(HL) by Catalytic Fast Pyrolysis and Hydrothermal Liquefaction

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5-16-2018 2:00 PM

Production of monomeric aromatics/phenolics from hydrolysis lignin (HL) by catalytic fast pyrolysis and hydrothermal liquefaction

Hooman Paysepar The University of Western Ontario

Supervisor Xu, Chunbao (Charles) The University of Western Ontario

Graduate Program in Chemical and Biochemical Engineering A thesis submitted in partial fulfillment of the equirr ements for the degree in Doctor of Philosophy © Hooman Paysepar 2018

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Recommended Citation Paysepar, Hooman, "Production of monomeric aromatics/phenolics from hydrolysis lignin (HL) by catalytic fast pyrolysis and hydrothermal liquefaction" (2018). Electronic Thesis and Dissertation Repository. 5381. https://ir.lib.uwo.ca/etd/5381

This Dissertation/Thesis is brought to you for free and open access by Scholarship@Western. It has been accepted for inclusion in Electronic Thesis and Dissertation Repository by an authorized administrator of Scholarship@Western. For more information, please contact [email protected]. Abstract

Bio-oil, produced from bio-feedstocks by thermochemical conversion technologies (e.g., pyrolysis or direct liquefaction), can be renewable replacement for petroleum for energy and chemical production. However, bio oil has high oxygen content, low stability, and low heating value. Thus, upgrading of bio-oil is necessary to remove the oxygen and make it a suitable substitute for conventional liquid transportation fuels or for value-added bio-based chemicals. Oxygen in a bio-oil can be removed by catalytic cracking or hydro-de-oxygenation to the form of H2O, CO and CO2 in the presence of a catalyst.

The overall objective of this PhD project was to develop novel technical solutions to production of monomeric aromatics/phenolics from hydrolysis lignin (HL) – a residue from cellulosic ethanol plants, for potential applications as fuels, fuel additives and chemicals. In this PhD thesis work, a catalytic fast pyrolysis (CFP) reactor system was in-house designed and constructed, and some novel zeolite-based solid acid catalysts with tailored strengths of acidity and improved resistance to carbon/coke deposition, such as acidified ZSM-5 catalysts, were developed to achieve a high yield (151 mg/g-HL) at a mild pyrolysis temperature (450C). In addition, hydrothermal liquefaction (HTL) – an emerging technology for biomass conversion under milder temperature (at 350C for 30 min) was employed to produce biocrude from hydrolysis lignin (HL) in water-ethanol (50:50, v/v) mixture with hematite ore as the catalyst. More importantly, the phenolics of the HL-derived biocrude was extracted and the phenolic extracts were used a bio-substitute to phenol for the synthesis of bio-phenol formaldehyde (BPF) resoles as wood adhesives. The dry bonding strengths of BPF resoles prepared with the phenolic extracts are higher than that of the BPF resoles prepared with the whole biocrude oils and the neat PF resole.

Keywords

Bio-oil, heavy oil (HO), hydrolysis lignin (HL), Xilinguole lignite (XL), fast pyrolysis (FP), catalytic fast pyrolysis (CFP), hydrothermal liquefaction (HTL), co-liquefaction, zeolite-X, zeolite-Y, H-ZSM-5, ZSM-5, hematite, iron ore, resin, phenol formaldehyde (PF) resole, bio oil phenol formaldehyde (BPF) resole, phenol extract (PE).

Co-Authorship Statement

Chapter 3: Catalytic fast pyrolysis of hydrolysis lignin for the production of aromatic/phenolic fuels or chemicals

Authors: Paysepar, H., Rao, K.T.V., Yuan, Z., Shui, H., and Xu, C.

The experiment work was conducted by Hooman Paysepar under supervision of Prof. Charles

(Chunbao) Xu and Prof. Hengfu Shui, and the guidance of Dr. Kasanneni Tirumala

Venkateswara Rao and Dr. Zhongshun Yuan. Writing and data analysis of this publication were conducted by Hooman Paysepar. It was reviewed and revised by Prof. Charles Xu and

Prof. Hengfu Shui. The manuscript is ready for submission to “Fuel”.

Chapter 4: Co-liquefaction of lignin and lignite coal for aromatic liquid fuels and chemicals in mixed solvent of ethanol-water in the presence of hematite ore

The experiment work was conducted by Hooman Paysepar under the supervision of Prof.

Charles (Chunbao) Xu, Prof. Hengfu Shui, and Prof. Shibiao Ren, and guidance of Dr. Shigang

Kang. Writing and data analysis of this publication were conducted by Hooman Paysepar. It was reviewed and revised by Prof. Charles Xu and Prof. Shibiao Ren. The manuscript was submitted to “Analytical and Applied Pyrolysis”.

Chapter 5: Zeolite catalysts screening for production of monomer aromatics/phenolics from hydrolysis lignin by catalytic fast pyrolysis.

Authors: Paysepar, H., Rao, K.T.V., Yuan, Z., Shui, H., Nazari, L., and Xu, C.

iii

The experiment work was conducted by Hooman Paysepar under supervision of Prof. Charles

Xu and Prof. Hengfu Shui, and the guidance of Dr. Kasanneni Tirumala Venkateswara Rao and Dr. Zhongshun Yuan. Writing and data analysis of theis publication were conducted by

Hooman Paysepar. It was reviewed and revised by Prof. Charles Xu and Dr. Hengfu Shui. The manuscript is ready for submission to a journal for publication.

Chapter 6: Improving activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis effect of acidic.

Authors: Paysepar, H., Rao, K.T.V., Yuan, Z., Shui, H., and Xu, C.

The experiment work was conducted by Hooman Paysepar under supervision of Prof. Charles

Xu and Prof. Hengfu Shui, and the guidance of Dr. Kasanneni Tirumala Venkateswara Rao and Dr. Zhongshun Yuan. Writing and data analysis of this publication were conducted by

Hooman Paysepar. It was reviewed and revised by Prof. Charles Xu and Prof. Hengfu Shui.

The manuscript is ready for submission to a journal for publication.

Chapter 7: Bio-phenol formaldehyde (BPF) resoles prepared using phenolic extracts from the biocrude oils derived from hydrothermal liquefaction of hydrolysis lignin.

Authors: Paysepar, H., Shanghuan Feng, Yuan, Z., Shui, H., and Xu, C.

The experiment work was conducted by Hooman Paysepar under supervision of Prof. Charles

Xu and Prof. Hengfu Shui, and the guidance of Dr. Shanghuan Feng and Dr. Zhongshun Yuan.

Writing and data analysis of this publication were conducted by Hooman Paysepar. It was

reviewed and revised by Prof. Charles Xu and Prof. Hengfu Shui. The manuscript is ready for submission to a journal for publication.

Dedication

My beloved wife, Fereshteh,

My wonderful parents, Hassan & Farideh,

For their endless love, encouragement, and support.

Acknowledgments

Many people have supported me during the completion of my thesis with insightful criticism, assistance, and expertise. This thesis would have never been possible without them.

I would like to express my sincere gratitude to my supervisors Professor Charles (Chunbao)

Xu at Western University and Prof. Hengfu Shui at Anhui University of Technology, Anhui

Province, China for their valuable guidance, continuous support, encouragement, advice and help throughout my PhD study.

My sincere appreciation is extended to Dr. Zhongshun (Sean) Yuan, Dr. Kasanneni Tirumala

Venkateswara Rao, Dr. Shibiao Ren, Dr. Shanghuan Feng for them priceless feedback, advice and guidance in the transition and completion of this research project.

In addition, I would like to thank my PhD supervision committee members, Dr. Cedric Briens and Dr. Dominic Pjontek, from the Institute for Chemicals and Fuels from Alternative

Resources (ICFAR), and my thesis examination committee (Dr. Ramin Farnood at U. of T.,

Drs. Yang Song, Sohrab Rohani and Cedric Briens at Western University), for their invaluable comments and suggestions.

I also gratefully acknowledge the financial support provided by the University of Western

Ontario Graduate Studies, the Department of chemical and Biochemical Engineering at the

University of Western Ontario (Teaching Assistantship, Graduate Research Scholarship),

NSERC/FPInnovations Industrial Research Chair Program in Forest Biorefinery and the

Ontario Research Fund-Research Excellence (ORF-RE) from Ministry of Economic

vii

Development and Innovation as well as the MITACS Accelerate Program. Support from the industrial partners including FPInnovations is also acknowledged.

I would also like to thank Fang (Flora) Cao and Thomas Johnston for their contributions and assistance in analyzing and characterization of my samples.

My deepest appreciation and sincere gratitude goes to my family, without whom I would have never been able to reach this point. Words cannot express how grateful I am to my parents for their love and support. At last, I would like to gratefully thank my beloved wife, Fereshteh

Najafi, for her patience, care, unconditional love, encouragement and support during all these years.

Hooman Paysepar

Western University

April 2018

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Table of Contents

Abstract ...... i

Co-Authorship Statement...... iii

Dedication ...... vi

Acknowledgments...... vii

Table of Contents ...... ix

List of Tables ...... xvi

List of Figures ...... xviii

List of Abbreviations and Symbols...... xxii

Chapter 1 ...... 1

1 General Introduction ...... 1

1.1 Introduction ...... 2

1.2 Background ...... 2

1.3 Research Objectives ...... 5

1.4 Thesis Overview ...... 6

1.5 References ...... 7

Chapter 2 ...... 9

2 Literature Review ...... 9

2.1 Sources of Lignocellulosic Biomass ...... 10

2.1.1 Cellulose ...... 11

2.1.2 Hemicellulose ...... 12

2.1.3 Lignin ...... 13

2.2 Thermochemical Conversion ...... 16

2.2.1 Combustion ...... 17

2.2.2 Gasification ...... 18 ix

2.2.3 Pyrolysis ...... 18

2.2.4 Hydrothermal Liquefaction ...... 19

2.2.5 Fractionation/pulping ...... 20

2.3 Pyrolysis Oil...... 21

2.3.1 Water Content ...... 22

2.3.2 Acidity...... 23

2.3.3 Viscosity ...... 23

2.3.4 Oxygen Content ...... 23

2.3.5 Heating Value ...... 23

2.4 Catalysts in Biomass Pyrolysis ...... 24

2.4.1 Microporous Catalysts ...... 27

2.4.2 Mesoporous Catalysts ...... 28

2.5 Extraction of Aromatics/Phenolics from Bio-oils...... 30

2.6 Phenol-Formaldehyde Resins/Adhesive ...... 31

2.7 Summary of the Literature Work ...... 34

2.8 References ...... 34

Chapter 3 ...... 49

3 Catalytic fast pyrolysis of hydrolysis lignin for the production of aromatic/phenolic fuels or chemicals ...... 49

Abstract ...... 50

3.1 Introduction ...... 51

3.2 Materials and methods ...... 54

3.2.1 Materials ...... 54

3.2.2 Catalyst characterization ...... 54

3.2.3 Experimental setup...... 55

3.2.4 Products separation ...... 57 x

3.2.5 Products analysis ...... 57

3.3 Results and Discussion ...... 58

3.3.1 Effects of the pyrolysis temperature on the product yields ...... 58

3.3.2 Char and gas analyses ...... 60

3.3.3 Bio-oils analysis ...... 62

3.3.4 Catalyst characterizations ...... 69

3.4 Conclusions ...... 75

3.5 Acknowledgments...... 75

3.6 References ...... 76

Chapter 4 ...... 83

4 Zeolite catalysts screening for production of monomer aromatics/phenolics from hydrolysis lignin by catalytic fast pyrolysis ...... 83

Abstract ...... 84

4.1 Introduction ...... 85

4.2 Materials and methods ...... 87

4.2.1 Materials ...... 87

4.2.2 Catalyst characterization ...... 87

4.2.3 Experimental setup...... 88

4.2.4 Product Separation ...... 90

4.2.5 Product characterization...... 91

4.3 Results and discussion ...... 92

4.3.1 Fresh catalysts characterization ...... 92

4.3.2 Effect of catalyst type on product yields ...... 94

4.3.3 Effects of catalyst on physical properties and elemental compositions of bio-oil ...... 96

4.3.4 Gas analysis ...... 99

4.3.5 Bio oil chemical compositions ...... 100

4.3.6 Spent catalysts characterization ...... 102

4.4 Conclusion ...... 113

4.5 Acknowledgments...... 114

4.6 References ...... 114

Chapter 5 ...... 119

5 Improving activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis ...... 119

Abstract: ...... 120

5.1 Introduction: ...... 121

5.2 Materials and methods ...... 122

5.2.1 Materials ...... 122

5.2.2 Catalyst Preparation ...... 123

5.2.3 Catalyst characterization ...... 124

5.2.4 Catalytic fast pyrolysis and vapor upgrading process...... 124

5.2.5 Product separation ...... 126

5.2.6 Products analysis ...... 127

5.3 Results and discussion ...... 128

5.3.1 Fresh catalysts characterization ...... 128

5.3.2 Effect of catalyst on products yields ...... 129

5.3.3 Gas analysis ...... 130

5.3.4 Bio-oil analysis ...... 131

5.3.5 Spent catalyst characterization ...... 137

5.4 Conclusions ...... 143

5.5 Acknowledgments: ...... 143

5.6 References: ...... 144 xii

Chapter 6 ...... 147

6 Catalytic co-liquefaction of lignin and lignite coal for aromatic liquid fuels and chemicals in mixed solvent of ethanol-water in the presence of a hematite ore ...... 147

Abstract: ...... 148

6.1 Introduction ...... 149

6.2 Experimental ...... 151

6.2.1 Materials ...... 151

6.2.2 Iron ore catalysts ...... 152

6.2.3 Experimental setup...... 153

6.2.4 Product separation ...... 153

6.2.5 Characterization of catalysts and liquefaction products ...... 155

6.3 Results and discussion ...... 156

6.3.1 Effects of temperature ...... 156

6.3.2 Effects of retention time...... 157

6.3.3 Synergy effect in co-liquefaction of lignin and lignite ...... 158

6.3.4 Co-liquefaction of lignin and lignite with catalyst ...... 160

6.3.5 Characterization of the liquefaction products ...... 162

6.4 Conclusions ...... 169

6.5 Acknowledgments: ...... 170

6.6 References ...... 170

Chapter 7 ...... 175

7 Bio-phenol formaldehyde (BPF) resoles prepared using phenolic extracts from the biocrude oils derived from hydrothermal liquefaction of hydrolysis lignin ...... 175

Abstract: ...... 176

7.1 Introduction ...... 177

7.2 Materials and methods ...... 179

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7.2.1 Materials ...... 179

7.2.2 Methods...... 180

7.3 Results and discussion ...... 185

7.3.1 Basic characterization of the BPF resoles ...... 185

7.3.2 Molecular weight and chemical structures of the BPF resoles and the bio- phenols ...... 187

7.3.3 Thermal stability and curing properties ...... 190

7.3.4 Bonding performance of the BPF resoles as wood adhesives ...... 198

7.4 Conclusion ...... 199

7.5 References ...... 200

Chapter 8 ...... 204

8 Conclusions and Future Work ...... 204

8.1 General Conclusions ...... 205

8.2 Contributions and Novelty ...... 209

8.3 Recommendations for Future Work...... 209

Appendices ...... 211

Appendix A: Production of bio-oil and aromatics by catalytic fast pyrolysis of woody biomass ...... 211

1.1 Materials ...... 211

1.1.1 Catalyst preparation ...... 213

1.1.2 Catalyst characterization ...... 213

1.2 Experimental apparatus ...... 214

1.3 Experimental procedure ...... 214

2 Characterization of bio-oil ...... 215

3 Effects of the sweeping gas flow rate, pyrolysis temperature, and catalysts on product yields ...... 216

References ...... 229 xiv

Appendix B: Permission to Reuse Copyright Materials ...... 230

Appendix C: Curriculum Vitae ...... 257

List of Tables

Table 2-1 Lignocellulosic biomass content [1]...... 10

Table 2-2 Typical properties of wood pyrolysis oil and heavy fuel oil [58]...... 21

Table 2-3 Catalysts used for bio-oil upgrading via catalytic cracking of bio-oil or pyrolytic vapors and their performance...... 26

Table 3-1 Results of elemental analysis of selective chars obtained from FP and CFP of HL at different temperatures...... 61

Table 3-2 Effects of catalyst on gas product distribution (% volume) at different temperatures...... 62

Table 3-3 Physical and chemical properties of the bio-oils...... 63

Table 3-4 Contents of 20 major monomeric phenolic compounds in the bio-oil products from CFP of HL with Zeolite X catalyst at various temperatures...... 66

Table 3-5 Contents of 20 major monomeric phenolic compounds in the bio-oil products from FP of HL without catalyst at various temperatures...... 67

Table 3-6 Acid properties of the fresh, spent, and regenerated Zeolite-X catalysts...... 71

Table 3-7 Textural properties of the fresh/spent zeolite X catalysts...... 74

Table 4-1 The properties of the 5 commercial zeolite catalysts...... 92

Table 4-2 Physical properties of bio-oils at 450 ᵒC...... 98

Table 4-3 Effect of catalysts on gas composition (vol.%) from fast pyrolysis of HL without and with various catalysts at different temperatures...... 99

Table 4-4 Total acidity values of all five Zeolite catalysts in fresh/spent/regenerated states...... 107

xvi

Table 4-5 Textural properties of the fresh, spent, and regenerate CBV-8014...... 113

Table 5-1 Textural properties of the fresh catalysts...... 128

Table 5-2 Gas composition (vol%) from the catalytic fast pyrolysis of hydrolysis lignin. .. 131

Table 5-3 Physical and chemical properties of the bio-oils...... 133

Table 5-4 Total acidity of the fresh, spent and regenerated catalysts of H₂SO₄-ZSM-5 and H₃PO₄-ZSM-5...... 140

Table 5-5 Textural properties of the acidified and metal loaded ZSM-5 catalysts...... 142

Table 6-1 Proximate and ultimate analysis of the HL and XL...... 151

Table 6-2 XRF analysis of the raw hematite ore...... 152

Table 6-3 Chemical and physical properties of the HOs from co-liquefaction of HL and XL at 400ᵒC for 2 h without and with hematite or reduced hematite catalyst...... 166

Table 6-4 Concentration of low-Mw aromatics/phenolics in HOs from co-liquefaction of XL and HL at 400ᵒC for 2 h...... 167

Table 7-1 Elemental composition and chemical contents of hydrolysis lignin...... 179

Table 7-2 XRF analysis of the raw hematite ore...... 180

Table 7-3 pH, solid content, viscosity and free formaldehyde content of all resoles...... 186

Table 7-4 Molecular weights and PDI of the BPF resoles and bio-phenols...... 187

Table 7-5 Thermal curing kinetic parameters for the resoles...... 194

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List of Figures

Figure 2-1 Schematic diagram of the molecular structure of cellulose[9]...... 11

Figure 2-2 Main components of hemicellulose [4]...... 13

Figure 2-3 Schematic structures of p-coumaryl, and sinapyl [13]...... 14

Figure 2-4 Different extraction processes to separate lignin from lignocellulosic biomass [20]...... 15

Figure 2-5 Thermochemical processes for biomass valorization...... 17

Figure 2-6 Bio-oil upgrading routes based on catalytic cracking: conventional method (a) and in situ method (b) [67]...... 25

Figure 3-1 Schematic diagram of the catalytic fast pyrolysis reactor...... 56

Figure 3-2 Product yields vs. temperature for FP of HL (a) compared with CFP of HL (b). . 60

Figure 3-3 GC-MS total ion chromatograms of bio-oils obtained from fast pyrolysis of HL with (a) and without (b) Zeolite X catalyst at 450 °C...... 65

Figure 3-4 Yields of phenolic compounds in bio-oils during FP (open) and CFP (solid) of HL at different temperatures...... 69

Figure 3-5 XRD patterns of fresh Zeolite-X (a), and spent Zeolite-X after experiments at 450ᵒC (b) and 500ᵒC (c) [46]...... 70

Figure 3-6 NH3-TPD curves of the fresh zeolite-X, spent catalysts after CFP of lignin at 450ᵒC and 500ᵒC, and these spent catalysts after regeneration ...... 71

Figure 3-7 TGA (a) and DTG (b) for the coke deposition on the spent zeolite-X...... 74

Figure 4-1 The catalytic fast pyrolysis reactor...... 90

xviii

Figure 4-2 Pyridine FT-IR spectra of the Zeolite-X, CBV-100, CBV-600, CBV-780, and CBV-8014 zeolite catalysts...... 94

Figure 4-3 Products yields in catalytic fast pyrolysis of hydrolysis lignin at various temperatures without or with various Zeolite catalysts...... 96

Figure 4-4 Yields of total monomeric aromatics/phenolics in fast pyrolysis of HL without/with zeolite catalysts at different temperatures...... 102

Figure 4-5 The XRD patterns of the fresh and spent catalyst of ZSM-5 (CBV 8014) after the 450 ᵒC experiment [31]...... 103

Figure 4-6 NH3-TPD profiles of all five Zeolite catalysts in fresh/spent/regenerated states.106

Figure 4-7 TGA-FTIR spectra of the evolved gas/vapour from spent catalysts of CBV-780

(a) and CBV-8014 (b) when heated from 340 to 600 ᵒC in N2...... 110

Figure 4-8 TGA/DTG profiles of the spent catalysts of CBV-8014 (a) and spent CBV-780 (b) heated from 25˚C to 800 ˚C in N2...... 112

Figure 5-1 Schematic diagram of the catalytic fast pyrolysis reactor...... 126

Figure 5-2 Pyridine FT-IR spectra of fresh catalysts of H₂SO₄-ZSM-5, H₃PO₄-ZSM-5, ZSM- 5, Ni-ZSM-5 and ZSM-5...... 129

Figure 5-3 Catalytic fast pyrolysis products yield over different catalysts at 450 ˚C...... 130

Figure 5-4 GC-MS total ion chromatogram of bi-oil obtain from catalytic fast pyrolysis of hydrolysis lignin over H2SO4-CBV8014 catalyst at 450 ᵒC. The labeling numbers are corresponding to the groups (1) through (4) of aromatics/phenolics...... 134

Figure 5-5 Compositions of GC-MS detectable aromatics/phenolics in bio-oils obtained with various catalysts...... 136

Figure 5-6 Total yield of monomeric aromatics/phenolics (mg/g-HL) obtained from CFP of HL over various catalysts at temperature 450 ᵒC...... 137

xix

Figure 5-7 X-ray diffraction patterns for the fresh and the spent catalysts of selected catalysts from pyrolysis of HL at 450 ᵒC for 20 min [21]...... 138

Figure 5-8 NH3-TPD profiles of the fresh, spent and regenerated catalysts of H₂SO₄-ZSM-5 and H₃PO₄-ZSM-5...... 140

Figure 5-9 TG (a) and DTG (b) profiles of the spent catalysts of H₂SO₄-ZSM-5, H₃PO₄- ZSM-5 and Ni-ZSM-5...... 141

Figure 6-1 Separation procedure of liquefaction products...... 155

Figure 6-2 Products distribution during co-liquefaction of HL and XL at various temperatures for 30 min residence time...... 157

Figure 6-3 Products distribution during co-liquefaction of HL and XL at 350 ᵒC for a residence time ranging from 0.5h to 2 h...... 158

Figure 6-4 Products distribution during liquefaction of individual HL or XL, and co- liquefaction of HL and XL at 350ᵒC for 30 min without catalyst...... 159

Figure 6-5 Products distribution during co-liquefaction of HL and XL with and without catalyst at 350ᵒC for 30 min (a), and 400ᵒC for 2 h (b)...... 161

Figure 6-6 XRD patterns of the raw hematite (a) and the reduced hematite (b)...... 162

Figure 6-7 FT-IR spectra of the XL, HL and the SR from the XL/HL co-liquefaction at 350 °C for 30 min...... 164

Figure 6-8 Gel permeation chromatograms of HOs from co-liquefaction of XL and HL at 400 ᵒC for 2 h without and with different catalysts...... 165

Figure 6-9 GC-MS spectra of the HO products from co-liquefaction of XL and HL at 400 ᵒC for 2 h...... 169

Figure 7-1 Extraction procedure for separation of phenolic extract from the biocrude oil. . 182

Figure 7-2 FTIR spectra of neat PF resole and all the BPF resoles...... 188 xx

Figure 7-3 FTIR spectra of the whole biocrude oils and the phenol extracts...... 189

Figure 7-4 DSC profiles of neat PF resole and BPF resoles heated at various rates...... 192

2 Figure 7-5 Linear plots of ln(β/Tp ) vs 1000/Tp and ln(β) vs 1000/Tp for all resoles based on the DSC measurements...... 196

Figure 7-6 TG and DTG profiles of the BPF and PF resole resins...... 197

Figure 7-7 Tensile strength of the three plywood samples bonded with the neat PF and BPF resole resins (dry strength: test after conditioning, wet strength: test after boiling in water for 3 h)...... 198

xxi

List of Abbreviations and Symbols

Abbreviation Meaning BPF Biocrude Phenol Formaldehyde

BTX Benzene, Toluene, and Xylene cP centipoise

C-BPF Catalytic Biocrude Phenol Formaldehyde

CFP Catalytic Fast Pyrolysis

DMA Dynamic Mechanical Analysis

DSC Differential Scanning Calorimetry

DTG Differential Thermal Gravimetric

E Activation Energy

FP Fast Pyrolysis

FTIR Fourier Transform Infrared Spectroscopy

GC-MS Gas Chromatography Mass Spectroscopy

GC-TCD Gas Chromatography Thermal Conductivity Detector

GPC Gel Permeation Chromatography

HHV High Heating Value

HL Hydrolysis Lignin

HLX Hydrolysis Lignin Zeolite-X

HNMR Proton Nuclear Magnetic Resonance

HO Heavy oil

HTL Hydrothermal Liquefaction

JIS Japanese Industrial Standard

xxii

NMR Nuclear Magnetic Response

PDI Polydispersity Index

PE Phenol Extract

PE-BPF Phenol Extract Bio-phenol Formaldehyde

PE-C-BPF Phenol Extract Catalytic Bio-phenol formaldehyde

PF Phenol Formaldehyde

R- Reduced

SR Solid Residue

TGA Thermogravimetric Analysis

THF Tetrahydrofuran

Tp Peak Curing Temperature

UTM Universal Testing Machine

WESO Water Ethanol Soluble Oil

WSP Water Soluble Product

XL Xilinguole Lignite

ZSM-5 Zeolite Socony Mobile-5

Z-X Zeolite-X

xxiii 1

Chapter 1

1 General Introduction

1.1 Introduction

The overall objective of this PhD project was to develop novel technical solutions to production of monomeric aromatics/phenolics from hydrolysis lignin (HL) – a residue from cellulosic ethanol plants, for potential applications as fuels, fuel additives and chemicals. In this PhD thesis work, a catalytic fast pyrolysis (CFP) reactor system was in-house designed and constructed, and some novel zeolite-based solid acid catalysts with tailored strengths of acidity and improved resistance to carbon/coke deposition, such as acidified ZSM-5 catalysts, were developed to achieve a high yield (151 mg/g-HL) at a mild pyrolysis temperature (450C). In addition, hydrothermal liquefaction (HTL) – an emerging technology for biomass conversion under milder temperature (at 350C for 30 min) was employed to produce biocrude from hydrolysis lignin (HL) in water- ethanol (50:50, v/v) mixture with hematite ore as the catalyst. More importantly, the phenolics of the HL-derived biocrude was extracted and the phenolic extracts were used a bio-substitute to phenol for the synthesis of bio-phenol formaldehyde (BPF) resoles as wood adhesives. The dry bonding strengths of BPF resoles prepared with the phenolic extracts are higher than that of the BPF resoles prepared with the whole biocrude oils and the neat PF resole.

1.2 Background

Recently, concerns about declining non-renewable fossil resources, energy security and their environmental impact are increasing worldwide. This has intensified the interest globally towards the development of alternatives to fossil fuels not only for energy security but also for chemical production. Biomass is renewable, carbon-neutral and abundantly available, and contains negligible sulfur, nitrogen, so it has been considered to be a promising substitute to fossil fuels for the production of energy and fuels, and the only renewable resource for chemicals [1].

Biomass contributes about 12% of today's world energy supply, whereas in many developing countries, its contribution ranges from 40 to 50%. It is, however, impossible to use solid biomass directly as an alternative fuel or chemical feedstock for industrial processes where fossil fuels, in particular oil, are used dominantly at present. It is necessary to develop technologies which make possible conversion of biomass to a more suitable form such as liquid or gas [2]. Thermochemical

biomass conversion processes, i.e., gasification, pyrolysis and liquefaction, have demonstrated to be effective for producing gas, liquid and solid fuel products [2]. A liquid product from biomass, bio-oil, can be readily stored and transported, accordingly separating the conversion and energy production processes, and can be used as a feedstock for chemical and material production [1,3]. Lignocellulosic biomass such as woody biomass contains approx.30-40% cellulose (linear polymer of C6 sugars), 25-35% hemicellulose (polymer of C5 and C6 sugars) and 20-30% lignin and 10% of ash and extractives [4]. Lignin, a natural, aromatic three dimensional high molecular weight biopolymer composed of phenyl propanol units [5], is a potential candidate for the production of fuels, aromatic chemicals and bio-based materials. All native lignins are heterogeneous in nature and mainly composed of two types of linkages: condensed linkages (e.g., 5-5 and β-1 linkages) and ether linkages (e.g., α-O-4 and β-O-4) [6]. According to the International Lignin Institute, about 40-50 million tonnes of kraft lignin (KL) are generated worldwide each year in the form of “black liquor”. While combustion of black liquor to regenerate pulping chemicals and to produce steam and power is an integral part of the kraft process, a small portion of the lignin can be removed without compromising mill material and energy balances. This presents an opportunity for revenue diversification, if value-added applications for kraft lignin can be identified. The interest in kraft lignin has reached a critical juncture. A commercial-scale, 75 t/d, lignin plant has been in operation since 2013 at Domtar’s Plymouth, North Carolina mill, and projects with targeted capacities of 30 t/d and 142 t/d are under construction in Hinton, Canada and Sunila, Finland, respectively. On the other hand, production of platform chemicals (e.g., lactic, succinic and other organic acids) from sugars is growing and the next generation of these technologies seek to use cellulose-derived sugar feedstocks. For this to be realized commercially, value-added applications are needed for the hydrolysis lignin (HL) by-products that are generated from cellulose hydrolysis. Value-added lignin by-products are also needed if the struggling cellulosic ethanol industry is ever to become commercially viable.

With pyrolysis, lignocellulosic macro-molecule compounds (cellulose, hemicellulose and lignin) are decomposed into vapors at an elevated temperature usually above 400-500C in inert atmosphere, followed by gas-phase homogeneous re-polymerization or condensation reactions to form oily products at a yield of 50-80 wt% depending on feedstock, heating rates and temperature, when a catalyst is not usually needed [2]. In the case of hydrothermal liquefaction (HTL), however,

feedstock macro-molecule compounds are decomposed/de-polymerized into reactive and unstable fragments of reduced molecular weights in the presence of a suitable solvent (such as water or organic solvent, or ionic liquid) and a catalyst (acid, base or solids), followed by stabilization and repolymerization into oily compounds having lower molecular weights. The low molecular weight pyrolysis oil, liquefied or de-polymerized products from HTL of lignocellulosic biomass or lignin have higher hydroxyl number and better reactivity, making them promising feedstock for the preparation of bio-based phenol formaldehyde (BPF) or bio-based polyurethane (BPU) or epoxy resin/foam materials [7,8]. It shall be noted however, pyrolysis is the only industrially realized process for biomass conversion by far,

Bio-oil is a complex mixture containing organic compounds which are formed by the thermal degradation of cellulose, hemicelluloses, lignin and other bio-molecules originally present in biomass [9]. Pyrolysis is a thermal decomposition process that takes place in the absence of oxygen to convert biomass into solid charcoal, liquid (pyrolysis oil or bio-oil), and gases at elevated temperatures. However, the biomass-derived oils cannot be used directly as fuels due to several poor properties, such as thermal instability, corrosiveness, poor volatility, high coking tendency, low heating value, and immiscible with petroleum fuels. The two key differences between bio-oils from pyrolysis and traditional petroleum or coal-derived oils are the high oxygen content and high unsaturated content in bio-oils. Therefore, upgrading commonly by catalytic hydrodeoxygenation (HDO) and zeolite cracking [10] is a necessary step of the lignocellulosic involves a series of complex reactions that can stabilize the bio-oil, reduces its oxygen content or eliminates the biomass or lignin-derived pyrolysis oil to meet the fuel specification.

Catalytic fast pyrolysis (CFP) of lignocellulosic biomass or lignin, via catalytic cracking of the pyrolysis vapor in-situ, can improve the aromatics/phneolics yield and oil quality via in-situ catalytic cracking and HDO [10]. However, several problems have emerged, including low selectivity toward monocyclic aromatic hydrocarbons (MAHs) – desirable products and high selectivity toward the polycyclic aromatic hydrocarbons (PAHs) and high potential of catalyst deactivation by carbon/coke deposition, which are not desirable for the high-value applications of bio-oils and industrial operations. For instance, Mihalcik et al. [11] reported that HZSM-5 yields 46.2% naphthalene ring compounds and only 46.7% MAHs. Thus, novel catalysts with high

selectivity towards target products MAHs or monomeric aromatics/phenolics and high resistance to carbon/coke deposition, must be developed to address the above problems [12].

1.3 Research Objectives

TASK 1: Catalytic fast pyrolysis (CFP) of lignocellulosic feedstock and hydrolysis lignin with different type of catalysts- a catalyst screening study, and optimizing the reaction conditions to achieve bio-oil products of a higher yield and better quality (aromatic/phenolic compositions, molecular weight, viscosity, etc.).

This Task established suitable reaction conditions (temperature, residence time) for achieving greater yield of bio-oil with higher concentration of aromatic/phenolic compounds for CFP of hydrolysis lignin with various zeolites: Zeolite X, Zeolite Y and ZSM-5.

TASK 2: Extracting aromatic/phenolic compounds from pyrolysis oils or HTL biocrude oils.

An effective extraction method was developed for concentrating phenolic compounds in pyrolysis oils or HTL biocrude oils.

TASK 3: Co-liquefaction of lignin and lignite for aromatic fuels and chemicals.

In this task, we aimed to produce aromatic fuels and chemicals via co-liquefaction of lignin and lignite in a low boiling point solvent (ethanol-water mixture) using inexpensive catalyst: iron ore such as hematite and goethite.

TASK 4: High value application of phenolic extracts for chemicals.

The phenolic extracts were used a bio-substitute to phenol for the synthesis of bio-phenol formaldehyde (BPF) resoles as wood adhesives.

1.4 Thesis Overview

The thesis consists of eight chapters organized in the following order:

Chapter 1 provides a general introduction to the importance of upgrading of bio-oil to a substitute for petroleum for energy and chemical production. The research objectives, research tasks accomplished, and thesis structure are outlined.

Chapter 2 presents a detailed overview of the available literature on fast pyrolysis, catalytic fast pyrolysis process, and hydrothermal liquefaction and their characteristics, focusing on upgrading of bio-oils. The applications of the aromatic/phenolic bio-oils are also described in this section.

Chapter 3 presents results of the catalytic fast pyrolysis (CFP)of hydrolysis lignin (HL) for the production of monomeric aromatic/phenolic compounds. The effect of process parameters on the yield of bio-oil and the yield of phenolic compounds were studied.

Chapter 4 presents a catalyst screening study with different zeolite catalysts including Zeolite- X, Zeolite-Y and ZSM-5 for CFP of HL. The yields of bio-oil and monomeric aromatics/phenolics were investigated. The fresh, spent, and regenerated catalysts were comprehensively characterized by NH3-TPD for the total acidity of the catalysts, thermogravimetric analysis (TGA) for evaluating the carbon/coke deposition on the spent catalysts, X-ray diffraction (XRD) for crystalline structure of the catalysts, and N2-isothermal adsorption for textural properties of the catalysts.

Chapter 5 focuses on tuning the acid strength and acid sites (Bronsted and Lewis sites) of ZSM- 5 catalyst to further enhance its activity and selectivity towards the production of monomeric aromatic/phenolic compounds. To the above end, different treatment approaches: acidification and metal loading, were employed, and the performance of the catalysts for CFP of HL were evaluated.

Chapter 6 describes an investigation on co-liquefaction of hydrolysis lignin and lignite for the production of aromatic/phenolic biocrude oils. The effects of variables including residence time, reaction temperature, solvent type, and the use of raw iron ore as an inexpensive catalyst were studied.

Chapter 7 describes an application of the whole phenolic bio-oil and phenolic extracts from the bio-oil as bio-phenols for the synthesis of bio-phenol formaldehyde (BPF) resoles. The BPF resoles were characterized for their physical/chemical properties, thermal curing by differential calorimeter scanning (DSC), and thermal stability by TGA. Plywood samples bonded with the BPF resoles were evaluated for their dry and wet bond strengths.

Chapter 8 presents the main conclusions obtained from the present research and suggests future studies.

1.5 References

[1] H.J. Park, J.K. Jeon, D.J. Suh, Y.W. Suh, H.S. Heo, Y.K. Park, Catalytic Vapor Cracking for Improvement of Bio-Oil Quality, Catal. Surv. from Asia. 15 (2011) 161–180. doi:10.1007/s10563-011-9119-7.

[2] A. Demirbaş, Mechanisms of liquefaction and pyrolysis reactions of biomass, Energy Convers. Manag. 41 (2000) 633–646. doi:10.1016/S0196-8904(99)00130-2.

[3] H. Zhang, R. Xiao, B. Jin, G. Xiao, R. Chen, Biomass catalytic pyrolysis to produce olefins and aromatics with a physically mixed catalyst, Bioresour. Technol. 140 (2013) 256–262. doi:10.1016/j.biortech.2013.04.094.

[4] Z. Fang, T. Sato, R.L. Smith, H. Inomata, K. Arai, J.A. Kozinski, Reaction chemistry and phase behavior of lignin in high-temperature and supercritical water, (2007). doi:10.1016/j.biortech.2007.08.008.

[5] A. Tejado, C. Peñ, J. Labidi, J.M. Echeverria, I. Mondragon, Physico-chemical characterization of lignins from different sources for use in phenol–formaldehyde resin synthesis, (2006). doi:10.1016/j.biortech.2006.05.042.

[6] F.S. Chakar, A.J. Ragauskas, Review of current and future softwood kraft lignin process chemistry, Ind. Crops Prod. 20 (2004) 131–141. doi:10.1016/j.indcrop.2004.04.016.

[7] Z. Yuan, S. Cheng, M. Leitch, C. Xu, Hydrolytic degradation of alkaline lignin in hot- compressed water and ethanol, Bioresour. Technol. 101 (2010) 9308–9313. doi:10.1016/j.biortech.2010.06.140.

[8] N. Mahmood, Z. Yuan, J. Schmidt, C. Xu, Production of polyols via direct hydrolysis of kraft lignin: Effect of process parameters, Bioresour. Technol. 139 (2013) 13–20. doi:10.1016/j.biortech.2013.03.199.

[9] C. Torri, M. Reinikainen, C. Lindfors, D. Fabbri, A. Oasmaa, E. Kuoppala, Investigation on catalytic pyrolysis of pine sawdust: Catalyst screening by Py-GC-MIP-AED, J. Anal. Appl. Pyrolysis. 88 (2010) 7–13. doi:10.1016/j.jaap.2010.02.005.

[10] P.M. Mortensen, J.-D. Grunwaldt, P.A. Jensen, K.G. Knudsen, A.D. Jensen, A review of catalytic upgrading of bio-oil to engine fuels, "Applied Catal. A, Gen. 407 (2011) 1–19. doi:10.1016/j.apcata.2011.08.046.

[11] D.J. Mihalcik, C.A. Mullen, A.A. Boateng, Screening acidic zeolites for catalytic fast pyrolysis of biomass and its components, J. Anal. Appl. Pyrolysis. 92 (2011) 224–232. doi:10.1016/j.jaap.2011.06.001.

[12] Y. Zheng, D. Chen, X. Zhu, Aromatic hydrocarbon production by the online catalytic cracking of lignin fast pyrolysis vapors using Mo2N/??-Al2O3, J. Anal. Appl. Pyrolysis. 104 (2013) 514–520. doi:10.1016/j.jaap.2013.05.018.

[13] C. Engtrakul, C. Mukarakate, A.K. Starace, K.A. Magrini, A.K. Rogers, M.M. Yung, Effect of ZSM-5 acidity on aromatic product selectivity during upgrading of pine pyrolysis vapors, Catal. Today. 269 (2016) 175–181. doi:10.1016/j.cattod.2015.10.032.

[14] Z. Yuan, N. Mahmood, J. Schmidt, M. Tymchyshyn, C. (Charles) Xu, Hydrolytic liquefaction of hydrolysis lignin for the preparation of bio-based rigid polyurethane foam, Green Chem. (2016) 2385–2398. doi:10.1039/C5GC02876K.

Chapter 2

2 Literature Review

This chapter supplies essential information on bio-oils derived from lignocellulosic woody biomass and lignin as bioresource alternatives for fossil-based chemicals, thermochemical conversion to obtain bio-oil, chemistry and application of bio-oils. Following a brief overview of bio-refinery, lignin and its chemical structure are presented. The production of aromatics/phenolics from lignocellulosic biomass through catalytic fast pyrolysis reaction is the main focus of this review. Furthermore, advances in the application of aromatic/phenolic bio-oil for production of bio-phenol formaldehyde resoles are introduced.

2.1 Sources of Lignocellulosic Biomass

There is a difference between biomass chemical composition and coal oil, oil shales, etc. The presence of large amounts of oxygen in plant carbohydrate polymers leads to variation of pyrolytic chemistry compared to fossil feedstocks. Lignocellulosic woody biomass is originally a composite material constructed from oxygen-containing organic polymers. Thus, based on the woody biomass main constituents (cellulose, hemicellulose, and lignin) the pyrolysis products form a complex mixture, and also is affected by the secondary reaction products that result from primary pyrolysis products cross-reactions [1]. The content percentage of cellulose, hemicellulose, and lignin vary by type of lignocellulosic biomass and three are presented in Table 2-1:

Table 2-1 Lignocellulosic biomass content [1].

Plant Material Lignocellulose Content (%)

Hemicellulose Cellulose Lignin

Orchard Grass (medium maturity) 40.0 32.0 4.7

Rice Straw 27.2 34.0 14.2

Birchwood 25.7 40.0 15.7

A short description of the characteristics and pyrolysis of cellulose and hemicellulose appears below. Once lignin is the main source of phenolic/aromatic compounds, we focus more on this component in this review.

2.1.1 Cellulose

Cellulose fibers contain 40-60 wt.% of dry wood and maintain wood’s strength [3]. Cellulose is a high molecular-weight (106 or more) linear polymer of β-(1 → 4)-D-glucopyranose units (Fig. 2- 1) [4]. Cellulose decomposition occurs at 240 -350 ˚C to produce anhydrocellulose and levoglucosan [5,6]. Cellulose can be converted to aromatics by catalytic fast pyrolysis. It is first pyrolyzed to anhydrosugars and other condensable oxygenated products like dihydroxyacetone and glyceraldehyde, and the anhydrosugars can be dehydrated and form furans, smaller aldehydes, and H2O [7,8].

Figure 2-1 Schematic diagram of the molecular structure of cellulose[9].

A study to investigate primary and secondary reactions in pyrolysis of cellulose can be found in Patwardhan et al. [10]. The oligomerization of levoglucosan and decomposition of primary products such as 5-hydroxymethylfurfural, anhydro xylopyranose, and 2-furaldehyde were the major secondary reactions occurring in a fluidized bed reactor [10]. Matsumura et al. [11] investigated the co-liquefaction of coal and cellulose in supercritical water concluding that cellulose can enhance the coal liquefaction and preferable liquefaction products by providing hydrogen for coal in the liquefaction process. Shoji et al. [12] worked on inhibition of char formation in FP of cellulose employing aromatic substances. They observed that only in FP with aromatic substances with polar substituents and high boiling points (> 400˚C) can completely inhibit char formation.

2.1.2 Hemicellulose

Hemicellulose (also named as polyose) is the second most common polymerized monosaccharide, such as glucose, mannose, galactose, xylose, arabinose, 4-O-methyl glucuronic acid and galacturonic acid in nature (Fig. 2-2). Lignocellulosic biomass usually contains 20 – 40 wt.% of hemicellulose, and has lower a molecular weight than cellulose [13]. The number of repeating saccharides in hemicellulose is ~150 while in cellulose it varies between 5000 – 10000 [14]. Hemicellulose decomposition occurs at temperature range of 200 – 260˚C [15].

The decomposition of hemicellulose is divided into two stages: the first step is dehydration and cracking of side units at a temperature around 100˚C, and then the main chain is decomposed at temperature range of 200 – 260˚C, producing more volatiles, less tar, and fewer chars than cellulose [16]. FP of hemicellulose extracted and purified from switchgrass was investigated by

Patwardhan et al. [17], they reported primary pyrolysis products as CO2, formic acid, Char, DAXP2, Xylose, acetol, CO, 2-furaldehyde, and AXP. Shen et al. [18] investigated the pyrolysis mechanism of the hemicellulose and the formation of main gaseous and bio-oil products. They proposed the probable routes for the creation of the products is from the decomposition of the three types of unit (xylan, O-acetyl xylan, and 4-O-methyl glucuronic acid). They found that the creation of CO was increased by increasing temperature, while slight changes in the yields of CO2 as predominant products in the gaseous mixture.

Figure 2-2 Main components of hemicellulose [4].

Pretreatment and enzymatic saccharification of corn fiber to sugars were reviewed by Saha [14], development and improvement of enzymes such as endo-xylanase, β-xylosidase, and α-L- arabinofuranosidase for bioconversion of hemicellulose were studied and bioprocess for large- scale conversion of hemicellulose to fuel ethanol, xylitol, 2,3-butanediol and other value-added fermentation products were described.

2.1.3 Lignin

The third major compound of wood is lignin, which has the composition 10 – 25 wt.% of dry wood [13]. Lignin is separated from cellulose fiber in the pulp and paper industry through different methods, such as chemical, biochemical, and physical [19–21]. Clarification of lignin structure plays a significant role in its application for chemicals and materials. Diverse analytical methods i.e. FTIR [22], NMR [23,24] and GPC [25] were used to discover the structure of lignin. Lignin is an amorphous cross-linked resin such as p-hydroxyl-phenyl propanol, guaiacyl-propanol, and syringyl-propanol which are mainly ether linkages together i.e. α-O-4, 5-O-4, and β-O-4 or condensed linkages i.e. 5-5, β-β, β-5and β-1 linkages. Lignin is a three-dimensional, highly branched, polyphenolic substance which includes irregular diversely bonded hydroxy- and methoxy- substituted phenylpropane units such as p-coumaryl, coniferyl, and sinapyl (Fig. 2-3) [4].

Two commercial separation processes are categorized as sulfur and sulfur-free, the resulted products from each of them are presented in Fig. 2-4. The physical and chemical properties of lignin vary based on the extraction or isolation technology applied to separate it. In addition to the lignin types shown in figure 4, another type of lignin is hydrolysis lignin (HL) which is produced through the FPI process, thermochemical pulp (TMP) bioconversion of hardwood, in which pretreatment of hardwood chips make them digestible biomass, then by enzymatic hydrolysis process sugars and HL are produced [26].

Figure 2-3 Schematic structures of p-coumaryl, and sinapyl [13].

The main monomer in softwood lignin is Guaiacyl, but hardwood lignin contains both Syringyl and Guaiacyl units [27]. In total, lignin consists of three types of the functional group including p- hydroxyphenyl, aliphatic hydroxyl, and carboxylic acid groups in which the reactivity of the lignin depends on the reactivity of the elevated functional groups [28].

Lignin is widely available as a by-product, present in black liquor, obtained in the production of pulp. It is mostly utilized in the pulp mills for heat and power generation i.e. recovery boilers [29], and a small portion of lignin is consumed as additives in printing inks, varnishes, and paints [30].

Whereas recently, it has been used as a feedstock for the synthesis of polymeric materials like adhesive resins [31]. Whilst lignin contains a phenolic polymer and by decomposition, at a temperature range of 290 – 500˚C an abundant oxygenates based on benzene rings, such as phenols are produced [15]. By pyrolysis of lignin, the polymer is depolymerized and phenols, guaiacols (2-methoxy-phenols) and syringols (dimethoxyphenols) and other substituted phenols are produced [32].

Figure 2-4 Different extraction processes to separate lignin from lignocellulosic biomass [20].

Characterization of six different types of lignin for depolymerization into aromatic monomers over solid acid catalysts was studied by Deepa and Dhepe [33]. They have shown that the SiO2 – Al2O3 catalyst gave exceptionally high yields of ca. 60% for organic solvent soluble extracted products with 95 ± 10% mass balance in depolymerization at 250˚C within 30 min. Base-catalyzed depolymerization was studied by Toledano et al. [34] for the valorization of lignin into monomeric phenolic compounds with focusing on avoiding repolymerization phenomenon by enhancing capping agent (phenol and boric acid) in order to increase the oil yield. They have reported that phenol experiments yielded high quantities of monomeric phenolic compounds (cresols, catechols, ferulic acid) while boric acid prevented to some extent the repolymerization phenomenon but it enhanced char production. A method for production of high value-added phenolics by combining

organosolv lignin extraction with lignin hydrothermal depolymerization without catalyst in aqueous ethanol was studied by Ye et al. [35] who reported that the highest yield of liquid products up to 65 vol% was recovered from lignin depolymerization under conditions of 523 K, 90 min, 65 vol% ethanol, and 3% lignin, only 17% solid residue was obtained. Yoshikawa and his coworkers [36] investigated the depolymerization and catalytic cracking of lignin for production of phenols. A new conversion process consisting of two reaction steps; in the first step, depolymerization of lignin was carried out in an autoclave reactor using silica-alumina catalyst in a water/1-butanol solution and in the second step, catalytic cracking of the liquid products from the first step was carried out using a fixed bed flow reactor over iron oxide catalyst, was investigated by them. The total recovered fraction of phenols and the conversion of methoxy phenol reached 6.6-8.6% and 92-94%, respectively.

2.2 Thermochemical Conversion

Thermochemical conversion is a commonly employed technique to upgrade biomass via both heat and chemistry including different possible routes to produce valuable fuels and chemicals. These processes are direct combustion, gasification, pyrolysis, hydrothermal liquefaction (HTL) and fractionation/pulping [13,37]. As shown in Fig. 2-5, the stored energy inside the biomass might be released directly as heat by combustion and co-firing. It can also be converted into liquid form

(e.g. bio-oils), solid (e.g. charcoal), or gaseous fuels (e.g. syngas) by pyrolysis, liquefaction, or gasification with different consumption purposes in the market.

Figure 2-5 Thermochemical processes for biomass valorization.

2.2.1 Combustion

The burning of biomass in air e.g. combustion which is the most extensively used process for biomass conversion, is handled for a different range of applications to transfer the chemical energy stored in biomass into heat, mechanical power, or electricity using various equipment such as furnaces, boilers, steam turbines, etc. [13,38]. It is feasible to burn any type of biomass; however, usually biomass with a moisture content of less than 50% is possible to burn and if the moisture content is higher, it would be better to be used it in biological conversion processes. There are three key steps that happen throughout the burning of biomass. In the first step drying, pyrolysis, and reduction occur, and in the second step combustion of volatile gases which provides more than 70% of the produced heat, and in the last step solid char is produced [13]. The combustion plant varied from very small scale i.e. domestic heating to large scale industrial plants.

2.2.2 Gasification

Gasification is a process that converts carbonaceous biomass into a combustible gas mixture ( H2, CO, CO2, and CH4) through the incomplete oxidation of the biomass ( normally 35% of the required O2 in complete combustion) at high temperatures, usually in the temperature range between 800 – 900˚C [38].

When air or oxygen is used, gasification is comparable to combustion, but is considered incomplete combustion. The difference between the two is their products, where combustion emphasizes heat generation, in gasification a valuable gaseous product is formed, which can be used directly for combustion, or stored for other utilizations; moreover, gasification is more environmentally friendly, as lower levels of toxic gases are emitted, and it also is more flexible in the application of solid by-products. On the other hand, gasification is comparable to a kind of pyrolysis process, which aims to produce more gaseous products [13]. The produced gas can be burnt directly or used as a fuel for gas engines and gas turbines, or a feedstock (syngas) in the production of chemicals like methanol and hydrogen.

2.2.3 Pyrolysis

Pyrolysis The pyrolysis process is a thermal decomposition of biomass in the absence of oxygen atmosphere and produces liquid oil, solid char, and non-condensable gas. Pyrolysis is an industrially recognized process for biomass conversion [39]. Three steps characterize a typical pyrolysis process through thermal gravity analysis (TGA): in the first step at a temperature range of 120 – 200˚C, pre-pyrolysis occurs with a slight weight loss related to some internal rearrangements i.e. bond breakage, free radicals, formation of carbonyl groups, and release of small amounts of water. Next, the key part of the pyrolysis process is solid decomposition, which involves considerable weight loss from the feedstock. The last step consists of char devolatilization through the cleavage of C-H and C-O bonds.

The pyrolysis process is divided into conventional (also named slow pyrolysis), FP and flash pyrolysis, depending on the heating rate and pyrolysis vapors residence time. Conventional slow pyrolysis (carbonization) has been used for thousands of years and has been mainly applied to charcoal production. It has a long residence time and temperature range of 300 – 700˚C, and also

a wide range of particle sizes can be employed in conventional pyrolysis. The thermal decomposition of biomass occurs at low heating rates so there is enough time for repolymerization reactions to increase solid yields [40,41]. The result, charcoal, has many applications, like domestic cooking and heating to metallurgical or chemical usage (e.g. the feedstock for the production of chemicals like activated carbon, fireworks, absorbents, soil conditioners, and pharmaceuticals) [42].

FP is usually applied at high heating rates (> 10 - 100 ˚C/s) and short residence time (0.5 - 10, typically < 2 s) [43]. It aims to maximize the yield of bio-oil products (50 - 70 wt.%). To increase its heating and heat transfer rates, a finely ground feed is typically used, and also to ensure a reaction, temperature (~500˚C) must be carefully controlled in the vapor phase; finally, the pyrolyzed vapors must be removed from the reactor and passed to the cooling section to increase bio-oil production. The bio-oils are constituted of an aqueous phase, which includes a low molecular weight of different light organo-oxygen compounds, and a non-aqueous phase (tar), which contains a high molecular weight of a wide range of insoluble aromatic organic compounds. By comparison, in flash pyrolysis, a higher heating rate (103 – 104 ˚C/s) and shorter residence time (< 0.5 s) are necessary. Thus, a higher bio-oil yield (75 – 80 wt.%) is produced [44,45]. The final product (bio-oil) from FP or flash pyrolysis can be simply stored and transported as any traditional liquid fuel.

2.2.4 Hydrothermal Liquefaction

Hydrothermal liquefaction (HTL) is a process at a temperature range of 280 – 370˚C and pressure range of 10 – 25 MPa [46]. Different processing parameters have changed the bio-oil yield in HTL e.g. temperature, particle size, biomass feedstock, biomass heating rate, solvent density, pressure, residence time, and reducing gas (hydrogen donors) [47]. In the HTL process, feedstock macro- molecule compounds are decomposed into fragments of light molecules in the presence of a solvent and a suitable catalyst. At the same time, these fragments, which are unstable and reactive, repolymerize into oily compounds having appropriate molecular weights [48]. In comparison with pyrolysis, a catalyst is usually unnecessary, and the light decomposed vapor fragments are converted to oily compounds through homogeneous reactions in the gas phase; in HTL, water

instantaneously works as a reactant and catalyst, which makes the process considerably varied compared to the pyrolysis process as water creates negative outcomes (as it decreases HHV) [46].

HTL is a green process, as it changes heteroatoms of hazardous materials like ammonia and NOx into low-risk by-products, compared to completely dissimilar combustion types which can be released into the air directly. In hydrothermal water conditions, biomass and oxygen quickly oxidize or mineralize to create CO2 or H2O, and heteroatoms of nitrogen in biomass mostly change to N2 with some N2O [47]. Similar to biomass liquefaction, liquefaction of coal to produce liquid transportation fuels has become an attractive approach for some countries such as South Africa, US, and China, where there are abundant coal reserves. Coal can be converted into liquid fuels by indirect coal liquefaction (ICL) or direct coal liquefaction (DCL). The gasification followed by catalytic conversion of syngas into clean hydrocarbons at the first conversion technique and in the latter process occurs at temperatures around 300–500°C under 5 –25 MPa H2 in an appropriate solvent with a suitable catalyst [48–50].

2.2.5 Fractionation/pulping

Biorefining, or biotechnology, is the process that converts renewable raw materials (biomass) into bio-based chemicals and fuels; and shares many likenesses with petrochemical refining. In both processes, the raw materials are separated into constituents that afford more useful intermediates that are more simply utilized than the first feedstock [51]. Pretreatment of lignocellulosic biomass includes a chemical, thermal, biological or mechanical process for the preparation of biomass for additional downstream processing in a biorefinery that can be used in the production of biofuels, biochemicals, cellulose-based materials, and lignin-based materials. Overall, if the lignocellulosic biomass that is processed achieves at least one of the following goals, it is called biorefinery [52,53]. 1- Fractionation into three main constituents (cellulose, hemicellulose, and lignin) for extra conversion to high-value bio-based products. 2- Production of main biofuels, with residues as by-products.

Changes to cellulose and hemicellulose biologically employing enzymes and microbes involve five major processes in applications as biofuels, biochemicals or in pulp industries including

chopping or grinding (size reduction), pretreatment to build cellulosic parts more responsive to enzymatic reaction, enzymatic saccharification for hydrolyzing cellulose and hemicellulose to fermentable sugars (monomeric sugars), microbial fermentation to change fermentable sugars into fuels and chemicals, and purification and recovery of the product, while the lignin can be used as a source of aromatic chemicals [52,54].

2.3 Pyrolysis Oil

Bio-oils, the liquid product from biomass pyrolysis, also known as pyrolysis oils, pyrolysis liquids, and bio-crude, are usually dark brown, free flowing liquids with a smoky odor. The physical properties of bio-oils are reported in many publications [47,55–57], and they have more than 400 identified compounds [58]. Bio-oil is not a product of thermodynamic equilibrium during the pyrolysis reaction but is produced in short reaction times through fast cooling to condensate pyrolysis vapors. Thus, bio-oils contain many reactive species and their chemical composition changes with time until they reach thermodynamic equilibrium.

Bio-oil is a complex mixture of different sized molecules derived from depolymerization and fragmentation of cellulose, hemicellulose, and lignin. Thus, as shown in Table 2-2, the elemental compositions of bio-oil and petroleum-derived oil differ. The most important properties of bio-oil are discussed in the next section.

Table 2-2 Typical properties of wood pyrolysis oil and heavy fuel oil [58].

Physical Properties Bio-oil Heavy Fuel Oil

moisture content, wt% 15-30 0.1

pH 2.5 -

Specific gravity 1.2 0.94

elemental composition, wt%

C 54-58 85

H 5.5-7.0 11

O 35-40 1

N 0-0.2 0.3

ash 0-0.2 0.1

HHV, MJ/kg 16-19 40

viscosity (at 50 ᵒC), cP 40-100 180

Solid, wt.% 0.2-1 1

distillation residue, wt.% up to 50 1

2.3.1 Water Content

Water in bio-oils could be due to original moisture in feedstock which is produced during pyrolysis through dehydration reaction. Hence, the water content in bio-oil varies from 15-30 wt.% based on the type of feedstock and pyrolysis reaction conditions. At elevated concentrations, water is miscible with the oligomeric lignin-derived components due to the solubilizing effect of other polar hydrophilic compounds i.e. low molecular weight acids, alcohols, hydroxy aldehydes, and ketones that are mostly produced by the decomposition of carbohydrates [60].

Water in bio-oil has some positive and negative effects on its properties. It could reduce the viscosity, thereby promoting fluidity in the oil, which is good for automatization and pumping of bio-oil and also leads to a more uniform temperature profile and a decrease in NOx emissions. On the other hand, water reduces the oil heating value, leading to a long ignition time and lower combustion rate in comparison with diesel fuels [61].

2.3.2 Acidity

Bio-oils contain significant amounts of carboxylic acids, such as acetic and formic acids, which cause low pH values of 2-3. Acidity causes increased corrosiveness in the oils, which becomes more severe at higher temperatures and with increases in water content. Therefore, high acidity resistance is needed for those materials in contact with the bio-oils, and an upgrading process is required before using bio-oil as transportation fuels [60].

2.3.3 Viscosity

The viscosity of the bio-oils can vary largely by type of biomass feedstock and pyrolytic process conditions. In a comparison between bio-oil and petroleum-derived oil viscosity, the first one decreases at higher temperatures much faster than the second. Thus, as is described previously, very viscous bio-oils can be pumped easily with moderate preheating. However, bio-oil viscosity increases with time, which could be a result of chemical reactions among different compounds present in the bio-oil forming larger molecules [60].

2.3.4 Oxygen Content

The oxygen content of the bio-oils is usually between 25-60 wt.% [59,62], and is distributed in more than 350 compounds depending on the biomass feedstock and pyrolysis reaction conditions. The most important issue between bio-oils, when compared to hydrocarbon fuels, is the presence of oxygen. Oxygen presence leads to a decrease in bio-oil heating value and immiscibility compared with hydrocarbon fuels, making them extremely unstable. Thanks to their complex composition, bio-oils have boiling points that range through a wide variety of temperatures. The single most abundant bio-oil component is water and the other main groups of compounds are hydroxy aldehydes, hydroxy ketones, sugars, carboxylic acids, and phenolics. Most of the last compounds are usually presented as oligomers with a wide range of molecular weights from 900 to 2500 [63].

2.3.5 Heating Value

Based on the type of biomass feedstocks, production processes, reaction conditions, and collecting efficiency, the bio-oil properties would vary. The low heating value of the bio-oils, which is only

40 – 50% [59] of the hydrocarbon fuels, is a result of high water and high oxygen content of the bio-oils.

2.4 Catalysts in Biomass Pyrolysis

The elimination of oxygen is necessary in preventing the undesirable properties of pyrolysis oil resulting from the chemical composition of bio-oil, which mostly consists of different classes of oxygenated organic compounds. The removal of oxygen allows the transformation of bio-oil into a liquid fuel that can be broadly accepted and is economically attractive. Hydrotreating and catalytic cracking are the two types of processes that have been used to remove oxygen from bio- oil. The first uses hydrogen to remove oxygen in the form of water, while the other accomplishes the removal of oxygen in the form of water and carbon oxides using solid acid catalysts like zeolites [64].

The current techniques for upgrading crude bio-oils include hydrogenation, esterification, catalytic cracking (or catalytic transformation) and catalytic reforming. Hydrogenation and esterification are more appropriate in upgrading bio-oil from FP as the pyrolytic bio-oil contains a lot of double bond compounds, such as aldehydes and ketones, and organic acids such as formic acid [65]. Those compounds can be saturated by hydrogen and esterified by alcohol to produce more stable hydrocarbons and more neutral esters. Fluid catalytic cracking (FCC) is the heart of the petroleum refinery process for upgrading heavy hydrocarbon molecules. During an FCC process, a hot catalyst is put in contact with heavy gas oil to produce cracked products and coke. It is anticipated that the FCC process could also be applied to oxygenated bio-oil components to produce hydrocarbon fuels. Similarly, catalytic pyrolysis could be integrated into FCC processes for simultaneous biomass liquefaction and upgrading [66]. Catalytic cracking accomplishes deoxygenation through simultaneous dehydration, decarboxylation, and decarbonylation reactions occurring in the presence of a catalyst [67]. Dozens of catalysts have been evaluated for the upgrading of pyrolysis oils or pyrolysis vapors, including microporous catalysts (ZSM-5, USY, etc.), mesoporous catalysts (MCM-41, FCC, MSU, SBA-15, Gamma-Al2O3, etc.), and macroporous catalysts (CaO, MgO, etc.) [8].

Since biomass pyrolysis reactions are highly endothermic, industrial pyrolyzers, commonly fluidized bed reactors or rotary kiln reactors, operate with a heat carrier such as heated sand particles [68]. Generally, there are two bio-oil upgrading routes based on catalytic cracking, i.e., the conventional method to upgrade bio-oil, and in situ method to upgrade the pyrolysis vapors, as described in Figure 2-6 [69]. For both methods, one of the major operating challenges is related to coke/carbon deposits in the catalyst surface and pores, which causes deactivation of the catalyst, although the deactivated catalysts can be regenerated by full combustion of the deposited coke at about 700°C [66,69].

Figure 2-6 Bio-oil upgrading routes based on catalytic cracking: conventional method (a) and in situ method (b) [67].

Since the bio-oils produced through pyrolysis are highly oxygenated with lower heating values, different catalysts have been tested to upgrade the quality of the oil by deoxygenation reactions to enhance the heating values of the oils. In particular, the concentration of oxygenates in the oil product can be reduced through catalytic cracking of bio-oil or pyrolytic vapors and replaced by aromatic/phenolic compounds in the resulted oil using solid acidic catalysts such as microporous materials (zeolites, Al2O3, SiO2) and mesoporous materials [32,69]. The catalysts used for bio-oil upgrading via catalytic cracking of bio-oil or pyrolytic vapors and their performance and selectivity toward aromatic/phenolic compounds production are summarized in Table 2-3. Zeolites have been the most widely used as catalysts in bio-oil upgrading via catalytic cracking and accounted as the most selective catalyst to produce high aromatics/phenolics content bio-oil (Table 2-3).

Table 2-3 Catalysts used for bio-oil upgrading via catalytic cracking of bio-oil or pyrolytic vapors and their performance.

Feed Reaction conditions Oil yield HHV of oil Aromatic/Phenolic H/C O/C References Temp. (w.t%) (MJ/kg) compounds (-) (-) Catalyst (C)

Wood pyrolysis bio-oil HZSM-5, HY 410-490 44.4 [70]

Beech sawdust 5% Fe/ZSM-5 500 51.2 26.9 44.2 (RA%) 0.3 [71]

Pubescence HZSM-5 420 46.1 3.2 (wt.%) [72]

Pine sawdust HZSM-5 400-500 53.7 24.8 12.4 (RA%) [73]

Aspen wood Blank 28.1 (RA%) [74]

Walnut shell HZSM-5 500 48.0 42.3 (RA%) [75]

Waste particle board Ga/HZSM-5 450-550 46.3 32.1 (RA%) [76]

Pine sawdust Mo-Cu/HZSM-5 500 45.6 29.2 40.8 (RA%) [56]

Rice husk ZSM-5 450-550 35.3 21.8 23.6 (RA%) 1.7 0.5 [77]

Pine wood Mo₂N/HZSM-5 750 8.4 (wt.%) [78]

Empty fruit bunch HZSM-5 500 37.0 31.0 40.3 (RA%) [79]

HHV: high heating value

RA: Relative Area

2.4.1 Microporous Catalysts

The conversion of bio-oil compounds over HZSM-5 involves a very complex combination of reactions, mainly consisting of cracking, deoxygenation, aromatization and polymerization reactions [80]. Among these reactions, the deoxygenation reactions and the cracking of non- volatile components were found to be the rate-determining steps in the bio-oil upgrading. It was proposed in the literature that the selectivity of hydrocarbons could be improved, either by choosing appropriate operating conditions to increase the cracking rate or by decreasing the coke formation rate or by operating at lower concentrations and low temperatures [67,69,81].

Upgrading of wood FP bio-oil has also been investigated with different zeolites such as ZSM-5, HZSM-5, HY, and silica-alumina. After catalytic upgradation, the bio-oil yield decreased significantly with increased hydrocarbon yields in the organic distillate fraction (ODF) in the following order: 4.4 wt.% (H-mordenite) < 5 wt.% (silicalite) < 13.2 wt.% (silica-alumina) < 14.1 wt.% (HY) < 27.9 wt.% (HZSM-5) [69]. ZSM-5 or HZSM-5 has a 3-dimensional pore structure with a pore size of 5.5–5.6 Å, which is suitable for aromatics and olefins formation [82]. It has been widely demonstrated that ZSM-5 or HZSM-5 can be one of the best catalysts for producing hydrocarbons due to its special pore structure and activity [8].

Developing processes with non-precious (expensive) metal-based catalysts with high efficiency and stability is crucial for the industrial growth of bio-oil production. Several kinds of non-precious metal catalysts (microporous) for oxygen reduction reaction (ORR) have been studied, including metal oxides, polyoxometalates, metal sulfides, and metal-N4 macrocyclic compounds, such as cobalt phthalocyanine and iron porphyrin compounds. In addition, nitrogen-doped carbon- supported catalysts (M-N/C, where M stands for metal, N/C for nitrogen-doped carbon support) have attracted attention because of their high ORR catalytic activities. M-N/C catalysts have been successfully synthesized from small molecules, macromolecules, and polymers as a catalyst precursor.

Numerous results have shown that the nature of the applied catalyst precursor and the process of the heat treatment are critical factors that determine catalytic activity; however, their mechanisms of action are not yet fully understood [83]. Lin and co-authors carried out catalytic fast pyrolysis

(CFP) of biomass with CaO in a fluidized-bed reactor [84]. The results indicated that the relative abundances of small-molecule compounds (furfural, furfuryl alcohol, etc.) increased with CaO as the catalyst given the dehydration reactions of the carbohydrates from cellulose/hemicellulose. Catalytic fast pyrolysis of biomass was also studied in a spout-fluid bed with CaO and MgO, where the results demonstrated that these catalysts enhanced the ring opening reactions of cellulose into furans and carbonyl compounds and have the ability to crack heavy compounds into smaller oxygenates [84].

Biomass CFP consists of two steps: biomass FP and pyrolysis vapors catalytic conversion. Firstly, Biomass is fast heated and converted into pyrolysis vapors, non-condensable gas (mainly CO and

CO2) and char, then the pyrolysis vapors reach the surface of the catalysts. The small-molecule oxygenates can enter microporous catalysts such as ZSM-5 and transform into aromatics and olefins via ORR reactions. However, large-molecule oxygenates from pyrolysis cannot enter the pores of microporous catalysts and would polymerize, forming coke on the catalyst surface, which decreases aromatics/olefin yields and rapidly deactivates the catalyst. On the contrary, mesoporous and macroporous catalysts can crack heavy compounds but cannot convert them into aromatics and olefins. These problems limit the development of CFP technology for biomass conversion [8].

2.4.2 Mesoporous Catalysts

In recent years, mesoporous catalysts, such as MCM- 41, SBA-15, FCC catalysts and MSU whose pore sizes (2-50 nm) are much larger than those of traditional zeolites, have attracted great interest for their potential to crack large molecules. These catalysts were found to show some promising effects for bio-oil upgrading. However, due to their poor hydrothermal stability and high production cost, it is difficult to use them in industrial scales for treating biomass pyrolysis vapors that have high water content [85].

Similar to zeolites, which have a high tendency for coke formation and aromatization reactions over the catalysts, thereby plugging the pores and deactivating the catalysts, the acidic MCM-41 and H-Y have a high tendency for coking reactions. In contrast, a large pore size would allow for more chemical compounds to enter through the pore system, which leads to more coke deposition.

Therefore, more aromatics are produced, as well as coke, which contributes to the fact that the coke formation on the H-Y catalyst was higher than that of the ZSM-5 catalyst [86]. Among the mesoporous materials, SBA-15 has been known to have highly ordered hexagonally arranged mesopores, thick walls, an adjustable pore size from 5 to 30 nm, and high hydrothermal and thermal stability [87]. However, SBA-15 is a pure silica material lacking acidity. Increasing its acid sites can be achieved by the incorporation of Al in the framework of the mesoporous silica by doping (one-pot synthesis) or post-grafting [88].

Some mesoporous materials have been studied for catalytic cracking of biomass FP vapors. Adam et al. [89] investigated the cracking effects of several Al-MCM-41 catalysts by using the pyrolysis– gas chromatography/mass spectrometry (Py–GC/MS) instrument, and the results revealed that these catalysts could eliminate levoglucosan, reduce large molecular mass phenols, and increase the yields of acetic acid, furans, small phenols, and hydrocarbons. A further study was conducted to test these catalysts in a lab-scale fixed bed reactor, where all the catalysts were found to increase the desirable products in catalytic bio-oils, and some Me-Al-MCM-41 (Me = Fe, Cu or Zn) catalysts improved the phenol yields. Triantafyllidis et al. [90] compared the performance of two mesoporous aluminosilicate materials (MSU-SBEA) to Al-MCM-41. The use of the MSU-S catalysts resulted in high yields of cokes and chars, and significantly low yields of organic liquids (more formation of PAHs and heavy fractions, and almost no acids, alcohols and carbonyls, and very few phenols) [90].

Mesoporous catalysts were used for biomass catalytic fast pyrolysis (CFP). For example, FCC catalysts have strong cracking effects for biomass pyrolysis vapors. The most likely polymerization precursors (2-methoxy- phenol, 2-methoxy-4-methyl-phenol, 4-ethyl-2-methoxy- phenol, 2-methoxy-4-vinyl phenol, 2,6-dimethoxyphenol, etc.) decreased, while mono-functional phenols, ketones, and furans increased with the FCC catalyst in the biomass pyrolysis process according to a study by Zhang et al. [8]. Qiang et al. [88] reported the catalytic effects of four catalysts by Py–GC/MS: the zeolite ZSM-5, two aluminosilicate mesoporous materials Al-MCM- 41 and Al-MSU-F, and a proprietary commercial catalyst alumina-stabilised ceria MI-575 in the catalytic pyrolysis of sawdust, and their results showed that although all the catalysts produced

aromatic hydrocarbons and reduced oxygenated lignin derivatives, ZSM-5 was still the most active catalyst in the catalytic pyrolysis of lignocellulosic materials [88].

2.5 Extraction of Aromatics/Phenolics from Bio-oils

Typically, lignocellulosic biomass (e.g. bark, sawdust, etc.) is used as a feedstock in the pyrolysis process to produce bio-based pyrolysis oil, char, and gas. The char is used to produce charcoal and activated carbon, for example in Brazil, where more than 40 million tonnes per year of wood is carbonized to get charcoal for steel production [91], and the bio-oil with low HHV, which is a complex mixture of different compounds, can be used as cheap fuel. This process has been replaced by the rapid growth of cracking technologies over the past few decades, since the isolation of aromatic and phenolic compounds from bio-oil allow the production of high-value bio-based chemicals.

The content of aromatics and mostly phenolic compounds in a bio-oil depends on the characteristics (mainly lignin content) of the feedstock as well as reaction conditions (temperature and catalyst) [63]. The amount of aromatic and phenolic chemicals in bio-oil can also be post- concentrated by developing a selective fractionation technique to separate or concentrate these aromatic and phenolic chemicals from bio-oil. Aromatics and phenols derived from lignocellulosic biomass pyrolysis oils are of high-value and demand chemicals. The extracted portion can be used in the production of fuel additives[92] or be further isolated to be utilized in phenol-formaldehyde (PF) resins [93,94], adhesives, especially in polymers, and as an intermediate in the synthesis of pharmaceuticals [95].

Different separation schemes were used by the researchers to obtain valuable compounds from bio-oil. Huang et al. [96] published a critical review on the separation technologies for biorefineries, including pre-extraction of hemicellulose and other value-added chemicals, detoxification of liquids and hyperbranched polymers, membrane pervaporation in bioreactors. A distribution coefficient at room temperature was measured by Won and Prausnitz [97] for the organic solvents in the presence of a phenolic solute (phenol, m-cresol, 3,4-xylenol, pyrocatechol, resorcinol, and o-chlorophenol). In another study, isolation of phenolic compounds from pyrolysis of Eucalyptus wood oil was investigated to recover valuable chemicals, including phenols, cresols,

guaiacol, 4-methyl guaiacol, catechol, and syringol. It was indicated that liquid-liquid extraction by alkali and organic solvents yielded a phenolic fraction and also the removal of phenols was made more efficient by enhancing highly alkaline conditions [91].

Murwanashyaka et al. [98] presented a study of a steam distillation and recovery of phenols from birch wood pyrolysis oil in a pilot plant reactor. They reported that the steam-distilled fractions were chemically and thermally stable for further purification processes. Effendi and his co-workers [94] published a study on the production and utilization of liquids from the thermal processing of biomass to replace synthetic phenol in phenol-formaldehyde resins. They believed that none of the phenolics production and fractionation techniques (fractional condensation and solvent extraction) can be substituted for 100% of the phenol content of the resins. Additionally, the use of fast pyrolysis oils from a wide variety of biomass feedstocks for the preparation of bio-phenol formaldehyde resins was studied. The low reactivity of those isolated phenolic compounds had a distinct impact on the performance of PF resins [99].

The supercritical fluid extraction of vacuum pyrolysis oil to extract cardanol and phenol was studied by Patel et al. [100], where pyrolysis oil from cashew nut shells and sugarcane bagasse was analyzed. Maximum oil yield (50 wt.%) with higher concentrations of phenol and cardanol was achieved at temperature ranges of 303-333 K, pressure ranges of 120-300 bar, and mass flowrate of 0.7-1.2 kg/h. Pyrolysis oil from lignocellulosic materials was used to investigate the isolation of phenolic compounds through the solvent-extracted method, the phenolic fraction contained phenol, o-cresol, guaiacol, m,p-cresol, 2,4-dimethylphenol, 4-methyl guaiacol, 4-ethyl guaiacol, 4-propyl guaiacol, eugenol, and isoeugenol [101]. Finally, Achladas [102] reported on the fractionation of phenol-rich Fir wood pyrolysis oil with silica gel open column chromatography. He indicated that about 12 -17% (w/w) can be achieved by his separation method.

2.6 Phenol-Formaldehyde Resins/Adhesive The conversion of biomass feedstocks into functional chemical intermediates and renewable fuels plays an important role these days by focusing on sustainable materials and addressing the global issue of fossil fuels and GHG emissions. The decomposition of carbohydrates, e.g. guaiacyl (G), syringyl (S), and p-hydroxyphenyl propane (p-H)-type, which are available in lignin, can create monomer phenolic groups [93]. In fact, during thermochemical (such as pyrolysis and

hydrothermal liquefaction) and biochemical conversions of cellulosic or lignocellulosic biomass, many phenol and derivative compounds are formed, such as phenol, guaiacol, cresol, eugenol, etc. In North America, more than 509 kilotonnes of adhesives were consumed in 2015, of which over 75% were formaldehyde-based adhesive resins such as urea-formaldehyde (UF), melamine- formaldehyde (MF), and phenol-formaldehyde (PF) [103].

Phenol-formaldehyde (PF) resins are produced by the reaction of phenol with formaldehyde, and are the first commercial synthetic resins [104]. PF Resins are classified into two types: resoles and the novolacs, which are produced by base catalysis (such as NaOH) with formaldehyde-to-phenol molar ratio (F/P > 1.0 normally 1.0-2.0), and acid catalysis (such as oxalic acid, hydrochloric acid or sulfonate acids) with F/P < 1.0, normally 0.7-1.0), respectively. In the reaction of phenol- formaldehyde with alkaline catalysis, resoles can be thermally self-cured (crosslinked) without needing a hardener, and they are widely used as wood adhesives. In contrast, a hardener (commonly Hexamethylenetetramine or HMTA) is needed for thermally curing novolacs, and novolacs are the normally used polymer matrix for fiber-reinforced plastics (FRP), and foundry adhesives [94,104,105].

Urea-formaldehyde (UF) resin, one of the most important formaldehyde resin adhesives, is a polymeric condensation product of formaldehyde with urea [106]. PF adhesives are widely consumed in the wood industry for their outstanding operations, such as high bonding strength, chemical stability, brilliant water resistance, and heat resistance. The usage of PF adhesives in the wood industry is almost double that of UF in the USA, Japan, and some European countries while the usage of UF adhesives is higher than PF adhesives in China due to the production cost of PF adhesives [107].

Phenol from petroleum is a costly raw material for PF resole production; moreover, given declining fossil fuels and petroleum resources, the phenol market is more challenging. Thus, interest in the production of bio-based phenol has increased in both academia and industry [68,95,108]. Modified PF adhesives with enzymatic hydrolysis lignin were studied by Jin et al. [107], where the produced adhesives were used to prepare plywood by hot-pressing. They reported that the performance of the modified adhesives and the plywood glued with them almost met the Chinese National Standard. In another work by Cetin and Ozmen [109], the application of lignin-based resin as an adhesive showed that particleboards bonded with phenolated lignin formaldehyde

resins (up to 30% lignin content) displayed similar physical and mechanical properties in comparison to particleboards bonded with PF resins.

The investigation of formaldehyde-free wood adhesives from kraft lignin and a polyaminoamide- epichlorohydrin (PAE) resin was investigated by Li and Geng [31]. The lignin adhesive was prepared by mixing an alkaline kraft lignin with PAE solution, at a weight ratio of 3:1 of lignin/PAE, resulting in the highest shear strength and the highest water resistance of the wood composites. The lignin fraction of bio-oil produced from wood in an auger fast pyrolysis reactor separated using water and methanol was investigated by Sukhbaatar [110], who used isolated pyrolytic lignin in PF resins synthesis at 30%, 40%, and 50% in phenol replacement levels. His evaluation results showed that up to 40% replacement of lignin into phenol is effective in synthesizing wood adhesive type PF resins.

Further, the usage of lignin-based resins, including lignin-phenol-formaldehyde, phenolated- lignin-formaldehyde, and commercial PF resin, as an adhesive in the production of particleboards was demonstrated by Cetin and Ozmen [109]. The physical properties were investigated. (e.g. internal bond, modules of rupture and modulus of elasticity). They reported that the particleboards bonded with phenolated-lignin formaldehyde resins (up to 30% lignin content) and exhibited similar physical and mechanical properties compared to commercial PF resins.

In another work by Feng et al. [111], the effect of bark extraction before liquefaction and liquid oil after liquefaction of bark-based phenol formaldehyde resoles showed that the liquid product from white birch bark liquefaction in water/ethanol (50:50, v/v) effectively operated in replacement of 50 wt.% of phenol in the synthesis of bark-based phenol-formaldehyde resin. They also examined extracted hydrothermal liquefaction oil from bark at 70% acetone and the fractionation of the liquefied oil in water as a replacement for 50 wt.% of phenol in the PF resole and compared the results with the neat PF resole. All the three resoles studied displayed lower thermal stability than the neat PF resole and all three resoles could meet the bond strength requirements as adhesives for plywood. Bark extraction before liquefaction led to less water resistance, while fractionated hydrothermal liquefaction oil after liquefaction improved the water resistance of the resole.

2.7 Summary of the Literature Work

This paper provides a critical review of various thermochemical conversion technologies, specifically focusing on catalytic fast pyrolysis, as well as challenges and opportunities for the future conversion of biomass into liquid fuels and chemicals including lack of appropriate approaches to produce high aromatics/phenolics content bio-oil and then extract phenols from bio- oil and application of extracted phenols. Some key findings are summarized below: 1. With the increase in the world’s energy and chemical demands associated with the limitations of traditional energy resources and declining fossil fuel sources, it is imperative to replace traditional energy and chemicals sources with renewable resources (biomass). 2. Lignocellulosic biomass is a promising resource for energy (bio-oil) and chemicals. 3. Pyrolysis is a promising industrial technology for the production of bio-oil, which can also be used as a feedstock for the thermochemical-based biorefinery. 4. Upgraded bio-oil by catalytic cracking or catalytic hydrogenation is a potential substitute for fossil liquid fuels, as it presents more than 400 identified compounds. 5. Zeolite catalysts with higher acidity or lower Si/Al ratios are effective in promoting cracking reactions of lignin into aromatic compounds in pyrolysis and quality of the pyrolysis oil. 6. Pyrolysis oil from lignocellulosic feedstock might be effective in replacing phenol in the synthesis of phenol-formaldehyde resins. 7. The industrial applications of phenolated bio-oil formaldehyde resin need to be investigated in future work.

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Chapter 3

3 Catalytic fast pyrolysis of hydrolysis lignin for the production of aromatic/phenolic fuels or chemicals

Abstract

Catalytic fast pyrolysis of hydrolysis lignin was investigated in a drop-tube fixed bed reactor at temperatures ranging between 400 – 800ᵒC using zeolite X as catalyst for the production of aromatic/phenolic fuel or chemicals. The yield of low molecular weight monomeric phenolics increased considerably while increasing the pyrolysis temperature from 400ᵒC to 450ᵒC, but decreased with further increasing the pyrolysis temperature. Zeolite X remarkably increased the yield of monomeric phenolic compounds in the catalytic fast pyrolysis of hydrolysis lignin at all temperatures (400 - 800ᵒC). No significant changes in the catalyst properties (crystallinity, acidity, textural structure) during fast pyrolysis of lignin suggesting high stability of the catalyst in the process. The superb activity and stability of the zeolite X catalyst might be owing to its strong acidity and low pore volume. Under the best reaction conditions tested in this study (450ᵒC, with zeolite X catalyst), the bio-oil yield was 50.5% in relation to the dry lignin, and the content of monomeric phenolics (mainly guaiacol, syringol, 4-methoxy-3-(methoxymethyl) phenol and metoxyeugenol) was 146.2 mg/g of bio oil.

3.1 Introduction

Nowadays liquid transportation fuels and chemicals are mainly produced from non-renewable resources (specially, petroleum and coals). As a result of declining fossil fuel reserves, fluctuating crude oil price, and increasing concerns over greenhouse gas emissions and climate change, there is an intensified interest in exploring environmentally friendly and renewable sources for fuels and chemicals. Biomass is considered to be the most promising and only alternative to fossil fuels for the production of liquid transportation fuels and chemicals, due to its abundance, renewability and huge potential of reduction of greenhouse gas emissions, in addition to its low contents of sulfur, nitrogen, and ash. Production of renewable chemicals and fuels from biomass has been becoming an attractive option [1–3]. Lignocellulosic biomass, e.g., forestry/agricultural biomass/residues, is abundant, sustainable and inexpensive source of carbon, consisting of three main components: lignin (20-40%), cellulose (30-50%) and hemicellulose (30-40%), depending in type of biomass. Lignocellulosic biomass has received increasingly more attention over the last 40 years for the production of chemicals and fuels via biological or thermochemical conversions [4,5]. Typical thermochemical conversion processes include combustion/co-combustion, pyrolysis, hydrothermal liquefaction and gasification [3]. Fast pyrolysis (FP) and gasification are accounted as the industrial realized thermochemical technologies for lignocellulosic biomass conversion, which is a thermal decomposition process taking place in the absence of oxygen, producing pyrolysis oil (or simply bio-oil) as the main product at a yield up to 60-70%, and bio-char (~20%) and gases (~20%) [3]. Among the various biomass conversion technologies developed, fast pyrolysis indeed has received most significant attention owing to its technology maturity and feedstock flexibility [6–8]. Without upgrading, the bio-oil products from fast pyrolysis cannot be directly used as a replacement for gasoline and diesel fuels due to their high oxygen content, high acidity and being corrosive. They are chemically and thermally unstable, as well as non-miscible with petroleum fuels, which makes it essential for bio-oil upgrading. Catalytic fast pyrolysis (CFP) aims at producing a better quality bio-oil product with improved properties (reduced oxygen content, lower acidity/corrosivity and higher heating values, etc.) by using catalysts such as zeolites [4,5,9,10]. Due to aromatic/phenolic polymer structure of lignin, it has been considered as a promising feedstock for CFP to produce renewable aromatic/phenolic fuel or chemicals[10].

During the catalytic fast pyrolysis process in the presence of zeolite catalysts, lignocellulosic materials were rapidly pyrolyzed to form pyrolysis vapor as the primary pyrolysis products that are predominantly oxygenated species, then the vapor entered into the pores of zeolite catalysts where they were catalytically converted via a series of reactions such as deoxygenation, decarbonylation, and oligomerization to the final aromatic/phenolic products, and the oxygen was removed mainly as CO, CO2, and H2O [10]. Of various catalysts studied to date, zeolites have received much attention due to their wide applications in cracking, relative strong acidity and unique microporous structures, vast availability, relatively low cost, and thermal stability [11,12]. Zeolite catalysts (e.g., ZSM-5, Mordenite, Ferrierite) have shown to be effective in selective deoxygenation of pyrolytic vapors, resulting in increased aromaticity and C/O molar ratio of the bio-oil products [5], [13–16] [17]. Several papers have reported the use of different types of zeolite catalysts in fast pyrolysis of lignocellulosic biomass. In a study by Uzun et al. [18] catalytic pyrolysis of waste furniture sawdust in the presence of ZSM-5 and H-Y (10 % of the biomass sample) was carried out and the maximum oil yield 37.5 and 30.0 %, respectively, was obtained at 500 ᵒC in a fixed-bed reactor system. The results also revealed that the yields of valuable organics (such as aromatics) were increased and acidic compounds decreased in the bio-oil by using of a zeolite catalyst. Different types of acidic zeolites were screened by Mihalcik et al. [5] in fast pyrolysis of lignocellulosic biomass and it was demonstrated that HZSM-5 (Si/Al = 23) and the pore size of 5.2 Å, was the most effective catalyst in vapor upgrading towards monomeric aromatic compounds formation. In a study by Ma et al. [4] different types of zeolite catalysts (with different pore sizes and Si/Al ratios) were tested, however, the highest aromatic oil yield (75 %) was obtained with H-USY (Y- type zeolite) that has the largest pore size (7.4 Å) but the lowest Si/Al ratio ( = 7), namely the higher number of acid sites, which was inconsistent with the findings of Mihalcik et al. [5]. Valorization of lignin for fuel through CFP in fluidized bed reactor at 400˚C is studied by Wild et al. [19]. They showed that the maximum oil yield was 21 wt.% and the phenolic fraction could reach up to 10 wt.%. However, there was a common challenge in processing lignin in fluidized bed reactors due to the thermoplastic behavior of lignin particles makes them melt during the feeding and agglomerate with the sand inside the fluidized bed reactor, although this challenge

could be partially addressed by selecting pyrolysis temperature at 400˚C. In another study by Custodis et al. [20], CFP of lignin was conducted in the presence of three mesoporous catalysts, Al-MCM-41, Al-SBA-15, and Al-MSU-J, in which no correlation of the product selectivity and yield with aluminum content and acidity of the catalyst was able to establish. Direct upgrading of vaporized lignin by CFP over HZSM-5 was investigated by Zhou et al. [21] in a fixed bed reactor that avoided the challenge of feeding, where they described that maximum oxygen free aromatics (70 wt.%) could be achieved at 600˚C. By far, the effects of Si/Al ratio for zeolite on the pyrolysis of lignocellulosic biomass or lignin are yet to be determined. Among all types of zeolites, zeolite type-X has very low Si/Al ratio (~

1.0) hence strong acidity with meso-porosity has been widely used for hydrogen storage or CO2 adsorption [22–24], while the performance of zeolite X (with very low Si/Al ratio) in pyrolysis of lignocellulosic biomass or lignin has not been reported. Moreover, the mesoporous structure of zeolite X might enhance the selectivity of smaller molecules such as monomeric aromatic/phenolic compounds, targeted in this work. Although zeolite catalysts have a common drawback in cracking or hydrocracking as they could be deactivated due to their high potential of coke deposition in the pores that masks the acid sites of the catalysts [25,26], it is thus of interest to investigate the performance of zeolite X in catalytic fast pyrolysis of lignocellulosic biomass for the production of monomeric aromatic/phenolic compounds and its stability during the CFP process. Most of the catalytic fast pyrolysis studies were focused on converting lignocellulosic biomass and lignin for the production of bio-oils for fuel applications (after hydro-treatment or cracking upgrading). However, fast pyrolysis of lignin could produce phenolic bio-oils rich in monomeric phenolics (phenol, guaiacol, and syringol compounds) [17], which can be utilized as aromatic fuel additives [27,28] or phenol replacement in the synthesis bio-based phenol formaldehyde resins/adhesives [29,30]. Therefore, this study aims to investigate the effects of zeolite X on fast pyrolysis of lignin, in particular hydrolysis lignin – a solid residue stream from cellulosic ethanol plants, at various temperatures in fixed bed reactor with respect to the yields, physical/chemical properties and contents of monomeric phenolics of the bio-oils products.

3.2 Materials and methods

3.2.1 Materials

The hydrolysis lignin (HL) used in this study, obtained from FPInnovations, was derived from Aspen wood that is composed of 30–55% cellulose, 15–35% hemicellulose and 5–31% lignin. HL is a residue produced in FPInnovations’s TMP-Bio process- by pretreatment of wood chips to make it more digestible biomass, followed by enzymatic hydrolysis to produce mixed sugars of xylose and glucose, and HL as the by-product of the process [31]. HL has the following textural compositions: 56.7% Lignin, 29.8% carbohydrates, 1.2% Ash and 12.3% others, with elemental compositions (dry basis): 49.76% C, 6.45% H, 0.33% N and balanced by 43.46% O. ACS reagent- grade acetone, purchased from Caledon Laboratory Chemicals (ON, Canada), was used as the reactor rising/washing solvent for product separation.

3.2.2 Catalyst characterization

The zeolite X powder with Si/Al molar ratio of 1.0 and particle size of >45µm was purchased from Sigma-Aldrich (USA) with CSA 1318-02-1. The catalyst powder was pelletized then crushed and sieved to particles of a size range of 420-850 µm. The regeneration of the used catalyst was performed by calcining the acetone-washed spent catalyst in a muffle furnace at 500°C in air for 4 h. The crystalline structure of the fresh/spent zeolite catalysts was characterized by X-ray diffraction (XRD) on a Rigaku–MiniFlex powder diffractometer (Woodlands, USA), using Cu-

Kα (λ = 1.54059 Å) over the 2θ range of 10°-70° with step width of 0.02°. Textural properties of the fresh/spent catalysts were measured by N2 isothermal adsorption at 77 K (NOVA 1200e surface area and pore size analyzer). The specific surface area was calculated using Brunauer-Emmett-

Teller (BET) method. Total pore volume was estimated using the volume of N2 gas adsorbed at a relative pressure (P/P0) of 0.99. Density functional theory (DFT) was used to calculate the pore size distribution based on N2 desorption isotherm. The total acidity of the catalysts was measured by NH3-Temperature Program Desorption (NH3-TPD), carried out on a Quantachrome ChemBET Pulsar TPR/TPD automated chemisorption analyzer. In a typical experiment, about 0.1 g of the sample was pre-treated at 300°C for 1 h under a flow of helium (99.9%, 120 cm3min-1). After pretreatment, the sample was saturated with anhydrous ammonia at 100 °C for 10 min and

subsequently flushed with He at the same temperature to remove any physisorbed ammonia. Then, TPD analysis was carried out by heating the sample in helium from ambient temperature to 600°C at 10 °Cmin-1 and the desorbed ammonia was measured by thermal conductivity detector. The coke content of spent catalysts was estimated by thermogravimetric analysis (TGA) on a PerkinElmer Pyris 1 TGA by heating the spent catalyst in 20 cm3min-1 flow of air from 40C to 800C at 10 Cmin-1.

3.2.3 Experimental setup

Catalytic fast pyrolysis (CFP) and non-catalytic fast pyrolysis experiments were carried out in a drop-tube/fixed bed reactor made of SS 316L tube (19 mm O.D., 673 mm length). The schematic diagram of the reactor is shown in Fig. 3-1. The reactor was heated in an electric furnace whose temperature was controlled by a temperature controller. The furnace temperature could be varied from 200ᵒC to 1200ᵒC. The flow rate of nitrogen gas, flowing downward through the biomass feeder and the reactor, was set and controlled with a mass flow controller meter (Brokenhorst High-Tech EL-FLOW). The temperature controller and mass flow controller meter were pre- calibrated and all the temperatures and gas flow rate are the actual values inside the reactor during the experiments, temperature was calibrated by putting a thermocouple on top of the catalyst bed. Fast pyrolysis of HL was carried out with and without catalyst at temperatures ranging from 400- 3 -1 800 ᵒC with sweeping N2 gas at a flow rate of 97 cm min . In a typical run, 2 g of feedstock was loaded into the feeder (25.4 mm OD tube) above the reactor separated from the reactor by a ball valve, and 0.4 g of quartz wool was put in the bottom of the reactor as a support for the catalyst- bed of 2 g of catalyst (for the CFP experiments) in the tubular reactor positioned in the hot-zone of the furnace, as illustrated in Fig. 3-1. In addition, for the CFP experiments, 0.4 g of quartz wool was loaded on the top of the catalyst-bed to separate the HL and pyrolysis char from the catalyst- bed. Before starting the experiment, the reactor and the feeder were vacuumed/purged thrice repeatedly to eliminate air inside the reactor system, and leak proof was ensured by pressurizing the reactor system with high-pressure nitrogen gas before each experiment. The reactor was then 3 -1 heated up to the desired temperature at 10-20 °C/min in 97 cm min flow of N2. After the reactor temperature reached to the specified temperature, the HL particles in the feeder was fed into the reactor rapidly by opening the ball valve and tapping the feeder for making sure all the feedstock

was fed into the reactor instantly and simultaneously by gravitational force and pressurized 3 -1 nitrogen. Assuming negligible change in total gas flow rate (97 cm min N2) during the pyrolysis experiments, the residence time of the vapor inside the 2 g catalyst bed with about 0.8 cm3 volume, was thus estimated to be < 0.5 s, with the heating rate estimated to be > 750 ˚C/s (according to gravitational and N2 pressure force to send the particles down). The vapor product was condensed into a liquid product in a condenser refrigerated at −6 °C. The non-condensable gaseous products were collected using a gas bag for 20 min after feeding the feedstock and passing through glass/quartz wools. After being cooled to room temperature, the reactor system including the tubular reactor and the condenser was washed with 150 cm3 of acetone for recovery of all liquid product (i.e., bio-oil).

Figure 3-1 Schematic diagram of the catalytic fast pyrolysis reactor.

3.2.4 Products separation

After the reactor was cooled down to room temperature, the reactor was opened and the whole reactor system was rinsed with 150 cm3 of reagent grade acetone to completely remove bio-oil on the inner reactor wall, on the solid residue (char) and catalyst bed, as well as in the condenser. The rinsing acetone was removed by evaporation under reduced pressure in a rotary evaporator at 45ᵒC, and the product was weighed and designated as bio-oil. The solid residue remaining on the top of glass wool and the spent catalyst were collected and oven dried at 105ᵒC to a constant weight to determine char yield, and to recover the spent catalyst. The overall yield (wt.%) of pyrolysis products were calculated based on the equation (3-1):

푚푎푠푠 표푓 푙𝑖푞푢𝑖푑, 푠표푙𝑖푑, 표푟 푔푎푠 (푔) Yield (bio-oil, char, or gas) (wt.%) = × 100 (3-1) 퐷푟푦 푚푎푠푠 표푓 푓푒푒푑 (푔)

3.2.5 Products analysis

The total volume of the produced gas collected in the gas bag was determined by injecting a known volume of air into the bag, based on the dilution factor calculated by the oxygen concentration measured by micro-GC-TCD (Agilent 3000 Micro-GC) equipped with dual columns (Molecular sieve and PLOT-Q) and thermal conductivity detectors. With the total volume of the gas and gas compositions of main species (CO2, CH4, CO and H2, C2 and C3 hydrocarbons), gas yields were determined. Elemental analysis of the HL feedstock, bio-oils and chars were analyzed with an elemental analyzer (CHNS-O Analyzer FLASHEA 1112 SERIES, Thermo Scientific), and their higher heating values (HHVs) were calculated based on the Dulong’s formula [2]. The water content of bio-oil was determined by Karl-Fisher titration method using a Mettler Toledo DL32 colorimetric titrator. The viscosity and pH values of bio-oil were measured with a viscosity meter (CAP 2000+ Viscometer, Brookfield) and pH meter (ORION 2STAR PHBenchtop, Thermo Scientific), respectively. The bio-oil products were quantitatively analyzed with a gas chromatograph-mass spectrometer [GC-MS, Agilent Technologies, 5977A MSD) with a SHRXI -5MS column (30 m × 250 mm × 0.25 mm) and a temperature program of 60ᵒC (hold for 2 min) → 120ᵒC (10 ᵒC/min) → 280 ᵒC (8

ᵒC/min, hold for 5 min)]. Compounds in the oil were identified by means of the NIST Library with 2011 Update and the concentrations of the low boiling point volatile compounds (including the target monomeric phenolics) in the bio-oil samples were determined using di-n-butyl ether (Alfa Aesar) as an internal standard. Molecular weight distributions of the bio-oils were measured by Waters Breeze GPC-HPLC instrument equipped UV detector using styragel HR 1 as the analytical column at 40 °C using 1 cm3min-1 THF as the mobile phase. Polystyrene narrow standards were used for calibration of the GPC-UV.

3.3 Results and Discussion 3.3.1 Effects of the pyrolysis temperature on the product yields

In each pyrolysis experiment (repeated at least for three times), the products namely char, bio-oil, and gas were obtained. Pyrolysis product yields were calculated based on mass fraction (%) of the specific product in relation to dry mass of the feedstock (i.e., HL). For most chemical processes, temperature is the most important operational parameter, particularly for endothermic processes such as the present lignin pyrolysis where the temperature plays a major role to provide heat required for decomposition of lignin molecules. In this work, CFP and fast pyrolysis (FP) of HL were carried out comparatively at various temperatures ranging from 400ᵒC to 800ᵒC, and the yields for bio-oil, gas, and char vs. temperature for CFP of HL compared with FP of HL are presented in Fig. 3-2. By increasing the temperature from 400ᵒC to 800 ᵒC, the char yield declined continuously from 38% to 22% in CFP of HL, or from 34% to 17% in FP of HL, while the gas yield increased dramatically from 12% to 39% (CFP of HL), or from 13% to 33% (FP of HL), which is believed to be caused by enhanced primary cracking of the lignin molecules and secondary cracking of the pyrolysis vapors at higher temperature [28, 29]. Comparing the results for CFP with those of FP, the presence of catalyst promoted the char and gas formation, likely due to the catalytic cracking of volatile vapor over the zeolite catalyst with acidic sites during the CFP process [9, 37]. Herewith, to distinguish from the primary chars formed by thermal cracking of the biomass feedstock, the carbon from catalytic cracking/condensation of the volatile vapors may be classified as the coke. Interestingly, the bio-oil yield did not show monotonic trends with increasing temperature. In CFP of HL, the bio-oil yield increased drastically while increasing temperature

from 400C to 500ᵒC, attaining a maximum bio-oil yield of 56% at 500ᵒC, but declined gradually with further increasing the temperature, accompanied by an appreciable increase in gas yield. Similar trend of bio-oil yield vs. temperature was observed in FP of HL, except that the oil yield (approx. 61 %) peaked at a higher temperature, i.e., 600ᵒC. Thus, the presence of the catalyst (zeolite X) although decreased the maximum bio-oil yield from 61% without catalyst to 56% with the catalyst, but lowered the peak-temperature by 100ᵒC, from 600ᵒC without catalyst to 500ᵒC with the catalyst. The above result suggests that secondary cracking of the pyrolysis vapor is thermodynamically and kinetically favored at an high temperature as widely reported in many literature studies [16,33,34].

(a) Fast Pyrolysis 100

Yield (wt.%) Yield 20

0 400 450 500 550 600 700 800 Temperature (ᵒC) Bio-oil yield Gas yield Char yield

(b) Catalytic Fast Pyrolysis 100

40 Yield (wt%) Yield 20

0 400 450 500 550 600 700 800 Temperature (C) Bio-oil Gas Char

Figure 3-2 Product yields vs. temperature for FP of HL (a) compared with CFP of HL (b).

3.3.2 Char and gas analyses

Table 3-1 presents the CHNO elemental compositions (mass fraction on dry basis) of selective samples of char obtained from CFP or FP of HL at 400ᵒC, 500ᵒC, and 700ᵒC. Carbon content in char increases with increasing reaction temperature as expected, accompanied by decreased O and H contents along with decreasing of char yield, where it shall be noted that the HL is sulfur-free lignin and hence the O content was calculated by difference, assuming that the sulfur content is negligible. Generally, when increasing temperature, cracking reactions of O-C and H-C bonds could be enhanced, leading to char with a higher C content but lower H and O contents, while producing more water as a part of pyrolysis -oil (Table 3-3) and more H2/CH4/CO gases (Table 3-2). As shown and discussed previously (in Fig. 3-2), the solid residue products contain both the HL residue (char) and the coke deposits (determined by TGA analysis) on the used catalyst. As shown in the schematic diagram of the catalytic fast pyrolysis reactor (Fig. 3-1), in the experiments the HL feed and the catalyst bed were not in physical contact, thus the presence of the catalyst should not affect the decomposition of the solid HL feed. Accordingly, the char yield can be considered the same in all experiments and equal to the char yield of the non-catalytic runs at the same temperature. Higher solid residue product yields in the CFP are credited to coke deposits on the

catalyst formed by catalytically driven vapor cracking/condensation reactions. Similarly, the effects of catalyst on char compositions are obvious and significant: generally, the use of catalyst increased H and N contents, but decreased C and hence HHV of the resulted chars, suggesting that the secondary chars formed by catalytic cracking/condensation of the volatile vapors during the CFP of HL contain higher H and N and lower C than the primary chars produced by thermal cracking of the biomass feedstock during the FP of HL.

Table 3-1 Results of elemental analysis of selective chars obtained from FP and CFP of HL at different temperatures.

FP without catalyst CFP with catalyst HL 400⁰C 500⁰C 700⁰C 400⁰C 500⁰C 700⁰C

C (%) 49.76 74.50 80.29 87.76 71.64 74.70 79.85

H (%) 6.45 3.79 3.11 1.76 3.97 3.24 2.01

N (%) 0.33 0.62 0.61 0.73 1.78 0.77 1.56

O (%)1 43.46 21.09 15.99 9.75 22.61 21.29 16.58

Char (%) - 32.79 27.78 17.78 38.19 29.41 23.47

HHV (MJ/kg)2 18.28 26.84 28.74 30.46 25.86 26.09 26.92

1 Calculated by difference (100% - C% - H% - N%) assuming negligible sulfur and ash contents; 2 Higher Heating

Value (HHV) calculated by Dulong formula, i.e., HHV (MJ/kg) = 0.3383C + 1.422(H - O/8)

The gas products from the CFP and FP of HL were analysed by GC-TCD and the results of the analysis (presented in volume %) at selective temperatures (400,500, and 700ᵒC) are shown in Table 3-2. As clearly shown and expected, increasing reaction temperature or the presence of the

Zeolite X catalyst produced more H2/CH4/CO gases, due to the enhanced cracking reactions of O- C, H-C and C-C bonds of the volatile vapors at a higher temperature or in the presence of acid

sites of the zeolite catalyst [8]. Moreover, the catalyst could also promote the deoxygenation reaction of oxygenated compounds to yield more CO [35].

Table 3-2 Effects of catalyst on gas product distribution (% volume) at different temperatures.

Catalyst Temp. (C) H2 CH4 CO CO2

400 1.1±0.0 17.0±0.0 78.8±1.4 1.2±0.0

None 500 5.7±0.1 23.7±1.9 69.0±5.2 0.0±0.0

700 7.2±0.1 25.3±3.1 58.6±6.4 0.4±0.0

400 1.1±0.0 19.2±0.0 76.8±0.0 1.1±0.0

Zeolite X 500 5.0±0.0 24.6±0.0 66.3±0.0 2.3±0.0

700 5.2±0.5 28.5±2.3 59.5±3.2 3.0±0.2

3.3.3 Bio-oils analysis

3.3.3.1 Physical properties and elemental compositions

The physical properties and elemental compositions of selective bio-oils derived from CFP or FP of HL with or without catalyst at various temperatures are comparatively listed in Table 3-3. As clearly shown in the Table 3-3, the presence of the catalyst in CFP of HL produced bio-oils with significantly better quality: lower viscosity (e.g., reducing from 7.10 mPa.s without catalyst to 5.60 mPa.s with catalyst at 400ᵒC ), increased pH values (3.3-5.0 without catalyst vs. 4.6-5.7 with catalyst), improved heating value (HHV = 12-17 MJ/kg vs. 20-22 MJ/kg), a higher C content (42- 47% vs. 53-56% ), lower O content (46-53% vs. 37-40%), lower O/C molar ratio (0.7-1 vs. 0.5- 0.6) and reduced aromaticity (H/C = 1.5-1.7 vs. 1.5). These presenting data showed that presence of catalyst could be a cause to the hydrodeoxygenation process that happen on the zeolite-X. The presence of the acidic catalyst was believed to promote hydrodeoxygenation/de-hydration

reactions [11], yielding more (CO, CO2) in the gas products (as evidenced in Table 3-2) and H2O in bio-oils (6.32-8.59% without catalyst vs. 11.4-15.5 with catalyst) as displayed in Table 3-3. On the other hand, the effects of catalyst on molecular weights of the bio-oils are less significant, whereas the Mw of bio-oil increases with increasing the pyrolysis temperature suggesting that repolymerization/condensation reactions of volatile vapors could be enhanced at a higher temperature [31,36,37].

Table 3-3 Physical and chemical properties of the bio-oils.

Temperature

Viscosity

Watercontent (%)

Type of catalyst

HHV

O/C ( O/C ( H/C

pH (

(g/mol)

(MJ/kg) Elemental composition, 3

(mPa.S) -

- -

(

)

) )

 (%,d.b.)

C H N O1 400 - 44.79 6.31 0.36 48.54 15.50 7.10 6.32 3.27 160 253 0.8 1.7 500 - 47.10 6.78 0.36 45.76 17.43 5.10 7.29 3.55 168 267 0.7 1.7 700 - 41.58 5.14 0.42 52.86 11.99 3.40 8.59 4.96 184 345 1 1.5 400 Z-X5 54.13 6.73 0.42 38.73 20.99 5.60 11.42 4.57 164 250 0.5 1.5 500 Z-X5 55.76 6.85 0.48 36.91 22.04 3.00 15.50 5.20 171 283 0.5 1.5 700 Z-X4 52.66 6.76 0.92 39.66 20.37 2.30 14.92 5.73 170 339 0.6 1.5 1By difference and assuming negligible sulfur and ash contents; 2Calculated by Dulong formula HHV (MJ/ kg) =

3 4 0.3383C + 1.422 (H - O/8); Measured at 50 ᵒC; Mn and Mw are the number-average and weight-average molecular weights determined by GPC-UV; 5Fresh Zeolite-X catalyst.

As shown in Fig.3-2, the product yields from FP and CFP at 500˚C are almost the same. However, the quality of the bio-oil from the CFP run improves (Table 3-3). Additionally, it is worthy to note that the HL feed (HHV of 25.10 MJ/kg) was converted at 500˚C to aromatic bio-oil (HHV of 17.44 MJ/kg in FP and 22.04 MJ/kg in CFP), gaseous products (HHV of 2.10 MJ/kg in FP and 2.16 MJ/kg in CFP), and char (HHV of 28.74 MJ/kg in FP and 26.09 MJ/kg in CFP), leading to the total recovery of energy of approx. 75% in FP and 81% in CFP.

3.3.3.2 Compositions and yields of monomeric phenolics by GC-MS

The produced bio-oil products were analyzed quantitatively for their compositions and yields of monomeric phenolics by GC-MS (pre-calibrated with pure compounds and using di-n-butyl ether as an internal standard). Due to the limitation of GC method (workable for low boiling point volatile compounds) and the complexity of chemical composition of pyrolysis bio-oil (containing a great number of high boiling point compounds), normally only about 10-40% of mass is detectable by GC-MS [35]. Typical ion chromatograms for CFP and FP oils are presented in Fig. 3-3, where 20 major phenolic compounds detected by GC-MS are labeled. The contents (in mg/g of bio-oil) of the 20 major monomeric phenolic compounds in the bio-oil products from CFP and FP of HL are summarized in Tables 3-4 and 3-5, respectively.

Figure 3-3 GC-MS total ion chromatograms of bio-oils obtained from fast pyrolysis of HL with (a) and without (b) Zeolite X catalyst at 450 °C.

Table 3-4 Contents of 20 major monomeric phenolic compounds in the bio-oil products from CFP of HL with Zeolite X catalyst at various temperatures. Phenolic concentration (mg/g of bio-oil) -OH HLX HLX HLX HLX HLX HLX HLX Compounds name MW group(s) 400ᵒC 450ᵒC 500ᵒC 550ᵒC 600ᵒC 700ᵒC 800ᵒC phenol 94 1 3.22 3.97 4.43 3.53 3.40 4.54 3.52 3-methyl phenol 108 1 - 0.58 1.09 2.39 1.30 2.04 2.05 Guaiacol 124 1 8.54 10.62 8.39 6.11 - - - p-Cresol 108 1 - - - - 1.52 2.67 4.99 2,5-dimethyl phenol 122 1 - 0.96 1.72 2.45 1.56 0.91 0.63 3,5-dimethylphenol 122 1 - - - - - 2.26 - Cresol 108 1 4.45 6.99 6.16 3.40 - - - 2,3,5-trimethylphenol 136 1 - - - - 0.57 0.51 - 4ethylguaiacol 152 1 3.28 4.52 4.06 2.32 - - - Catechol 110 2 - - - - 6.81 - - 3-Metoxy-1,2-benzendiol 140 2 5.17 6.20 6.30 7.44 - - - 2-Methoxy-4-vinylphenol 150 1 8.39 11.96 8.93 6.41 - - - Methylcatechol 124 2 - - - - 2.68 - - Eugenol 164.2 1 2.37 4.52 4.39 3.05 - - - Orcinol 124 2 - - - - 3.60 - - Syringol 154 1 42.26 37.72 29.79 14.60 - - - 4-ethylresorcinol 138 2 - - - - 1.92 - - Isoeugenol 164 1 7.57 10.94 9.80 5.43 - - - 4-Methoxy-3-(methoxymethyl) 168 1 16.54 19.77 16.94 8.69 - - - phenol Metoxyeugenol 195 1 23.95 27.44 21.38 7.74 - - - Sum 125.72 146.19 123.37 83.56 23.35 12.93 11.18

Table 3-5 Contents of 20 major monomeric phenolic compounds in the bio-oil products from FP of HL without catalyst at various temperatures. Phenolic concentration (mg/g of bio-oil) -OH HL HL HL HL HL HL HL Compounds name MW group(s) 400ᵒC 450ᵒC 500ᵒC 550ᵒC 600ᵒC 700ᵒC 800ᵒC phenol 94 1 3.20 8.58 3.53 8.13 2.46 3.13 2.36 3-methyl phenol 108 1 - 1.43 - 1.71 0.94 1.41 1.37 Guaiacol 124 1 8.45 16.70 8.62 10.07 - - - p-Cresol 108 1 - - - - 1.10 1.84 3.35 2,5-dimethyl phenol 122 1 - 0.73 - 1.47 1.13 0.63 0.42 3,5-dimethylphenol 122 1 - - - - - 1.56 - Cresol 108 1 4.73 6.72 4.55 1.59 - - - 2,3,5-trimethylphenol 136 1 - - - - 0.41 0.35 - 4ethylguaiacol 152 1 3.20 5.09 2.96 3.94 - - - Catechol 110 2 - - - - 4.93 - - 3-Metoxy-1,2-benzendiol 140 2 4.83 3.19 4.41 3.07 - - - 2-Methoxy-4-vinylphenol 150 1 7.26 6.04 7.53 7.55 - - - Methylcatechol 124 2 - - - - 1.94 - - Eugenol 164.2 1 1.79 1.61 2.00 4.26 - - - Orcinol 124 2 - - - - 2.61 - - Syringol 154 1 41.87 39.91 37.43 17.86 - - - 4-ethylresorcinol 138 2 - - - - 1.39 - - Isoeugenol 164 1 6.21 6.70 7.07 4.32 - - - 4-Methoxy-3-(methoxymethyl) 168 1 15.64 14.79 13.46 7.41 - - - phenol Metoxyeugenol 195 1 21.28 13.37 22.20 2.45 - - - Sum 118.44 124.87 113.76 73.84 16.91 8.92 7.50

The contents of 20 major monomeric phenolic compounds in the bio-oil products from CFP of HL with/without Zeolite X catalyst at various temperatures, as presented in above Tables 3-4 and 3-5, show that, the compositions of the bio-oils are strongly dependent on the pyrolysis temperatures employed. The detectable phenolic compounds in the HL-derived bio-oils by GC-MS are mostly monomeric phenolics, i.e. alkyl-phenols, derived from lignin’s macromolecules. It can be observed from both Tables that, the most abundant monomeric phenolics in the HL-derived bio-oils (irrespective of the presence of catalyst) are Guaiacol, Syringol, 4-Methoxy-3-(methoxymethyl) phenol and Metoxyeugenol, at all temperatures. Moreover, the monomeric phenolics are most

68 enriched in the pyrolysis oils obtained at 400 – 500ᵒC temperatures, but sharply decreased at temperatures above 500ᵒC, likely due to enhanced cracking of C-C bonds of volatile vapors at higher temperatures [10,39] to form gases, leading to the formation of more gases and less oils (as evidenced by the results in Fig. 3-2), or enhanced re-polymerization/condensation reactions of volatile vapors at higher temperatures [40–42] to form oligomers or condensed oils with larger

Mw, as illustrated previously in Table 3-3.

As shown in Table 3-4, the total content of detected phenolic compounds in the CFP oil is 125.7 mg/g at 400ᵒC and increases to as high as 146.2 mg/g at 450ᵒC and then decreases when further increasing the temperature, and to as low as 11.2 mg/g at 800ᵒC. The same trend was observed for the FP oils. Comparing between the contents of phenolic compounds in the FP and CFP oils, one may conclude that the presence of Zeolite X catalyst led to increased contents of almost all monomeric phenolic compounds in the oils at all temperatures. This result suggests that the use of Zeolite X catalyst in pyrolysis of HL or other lignocellulosic biomass could catalyze cracking of nonvolatile oligomers into monomeric compounds [9], and produce bio-oils with higher contents of phenolic compounds, as similarly observed in the literature work [43].

Fig. 3-4 presents yields of phenolic compounds (g/g of HL) in bio-oils during FP and CFP of HL at different temperatures. Similarly, as presented and discussed previously, during FP and CFP of HL the yield of monomeric phenolic compounds peaked at 450ᵒC, while decreased sharply at > 500C. For instance, the yield of monomeric phenolic compounds was 0.057 and 0.074 g/g of HL during CFP of HL at 400ᵒC and 450ᵒC, respectively, but it was as low as 0.005 g/g of HL at 800ᵒC. The similar trend was reported in a study by Thangalazhy-Gopakumar et al. [44], where the concentration of phenol and its derivatives increased with the increase in pyrolysis temperature whereas the concentration of guaiacol and its derivatives decreased as the temperature increased. Again, as shown in Fig. 3-4, the use of Zeolite X catalyst in pyrolysis of HL led to higher yield of volatile monomeric phenolics, which could be attributed to the catalytic cracking of non volatile oligomers into monomeric compounds [9,45].

0.08

0.07

0.06

0.05

0.04

(g/g ofHL) 0.03

0.02

0.01 Yields of monomeric aromatic/phenolic ofmonomeric Yields

- 350 400 450 500 550 600 650 700 750 800 850 Temperature (C)

Figure 3-4 Yields of phenolic compounds in bio-oils during FP (open) and CFP (solid) of HL at different temperatures.

3.3.4 Catalyst characterizations

3.3.4.1 Catalyst crystalline structure

XRD patterns of the fresh and spent zeolite-X catalyst after CFP of lignin at selected temperatures 450ᵒC and 500ᵒC (i.e. the best temperatures for phenolic bio-oil yield) are shown in Fig. 3-5. The characteristic peaks of zeolite X do not change much after CFP experiments at these temperatures when compared with those of the fresh catalyst. The height of the strongest peak at 2Ѳ = 30.04ᵒ, was commonly used to calculate the degree of crystallization, based on which the spent catalysts almost remained their crystallinity, being 96% and 98% of that of the fresh catalyst at 450ᵒC and 500ᵒC, respectively. The results indicate that the zeolite-X catalyst showed superb thermal stabilities of the framework during the CFP operations. Similar stability was reported for ZSM-5 zeolite catalysts [46,47].

(c)

(b)

(b) XRD intensity (a.u.) intensity XRD

(a)

10 20 30 40 50 60 70 2-Theta (deg.)

Figure 3-5 XRD patterns of fresh Zeolite-X (a), and spent Zeolite-X after experiments at 450ᵒC (b) and 500ᵒC (c) [46].

3.3.4.2 Catalyst acidity analysis

The NH3-TPD patterns for the fresh (Zeolite-X) and spent catalyst (Zeolite-X-450 and Zeolite-X- 500) after CFP of lignin at selected temperatures 450ᵒC and 500ᵒC, and these spent catalysts after regeneration (R-Zeolite-X-450 and R-Zeolite-X-500) are shown in Fig. 3-6, and the integrated values corresponding to the total acidity of the samples are shown in Table 3-4. As shown in the

Fig. 3-6, all zeolite-X catalysts show profiles with two NH3-desorption peaks at around 200ᵒC and 460ᵒC, which are often defined as weak and strong acid sites, respectively. From Fig. 3-6 it can be seen that the spent zeolite-X’s intensity and area of both strong acid and weak acid peaks are lower than those of the fresh catalyst, which appears that the amounts of strong acid (Bronsted acid) and weak acid (Lewis acid) sites were reduced in these spent catalysts after the high temperature experiments [48,49]. However, since the sample amounts used in the NH3-TPD analysis were not exactly same, conclusions should not be drawn simply based on the NH3-TPD patterns as shown in Fig. 6. In fact, from the total acidity (mmol/g) values as shown in Table 6, the total acidity of the spent catalyst (~1.27-1.28 mmol/g) remains almost the same when

71 comparted with that of the fresh catalyst (1.16 mmol/g), again suggesting strong stability of the zeolite-X during the CFP of lignin.

9 Zeolite-X 8 Zeolite-X 450 7 Zeolite-X 500 6 R-Zeolite-X 450 5 R-Zeolite-X 500 4

3 TCD Signal (mV) Signal TCD 2 1 0 100 200 300 400 500 600 Temperature (ᵒC)

Figure 3-6 NH3-TPD curves of the fresh zeolite-X, spent catalysts after CFP of lignin at 450ᵒC and 500ᵒC, and these spent catalysts after regeneration

Table 3-6 Acid properties of the fresh, spent, and regenerated Zeolite-X catalysts.

Catalyst Total acidity (mmol/g)

Z-X1 1.16

S-Z-X 4502 1.27

S-Z-X 5002 1.28

R-Z-X 4503 2.01

R-Zeolite-X 5003 2.04

1Fresh Zeolite X catalyst; 2Spent Zeolite X catalyst from 450C or 500C CFP experiment;

3Regenerated Zeolite X catalyst from 450C or 500C CFP experiment.

More interestingly, as illustrated in both Fig. 3-6 and Table 3-6, the regenerated catalysts have significantly increased weak acid (Lewis acid) sites, much higher than the spent and fresh catalysts, although the strong acid (Bronsted acid) sites remain the same. Some possible causes that lead to the increased Lewis acid sites are discussed here. As well known, the Bronsted acid sites of zeolite are created by aluminum substituting silicon in a tetrahedral zeolite framework, requiring a cation to satisfy the Al tetrahedron, and quite often the cation is a proton, forming a strong Bronsted acid site. Thus, the acidity of a zeolite increases by increasing the Al/Si ratio (or decreasing the Si/Al ratio). In the CFP experiments and the regeneration (calcination) operations, the Si/Al ratio of the zeolite would not likely change, so their strong acid (Bronsted acid) sites remain the same, as evidenced in Fig. 3-6. On the other hand, however, Lewis acidity of zeolite generally results from extra-framework aluminum, which is not tetrahedrally bound in the zeolite framework. Thus, during the pyrolysis and regeneration (calcination) operations, extra-framework aluminum is expected to change specially for zeolite-X with high framework aluminum by the high-temperature treatment that removes Al from the framework to the extra-framework, hence increasing the Lewis acidity, as shown in Fig. 3-6 and Table 3-6.

3.3.4.3 Carbon/coke deposition on the catalyst

In order to determine the extent of carbon/coke deposition during CFP of HL, thermogravimetric (TG) and differential thermogravimetric (DTG) measurement of the spent catalysts from the 450ᵒC and 500ᵒC experiments were conducted at a heating rate of 10 ᵒCmin-1 from 40 ᵒC up to 800ᵒC under 20 cm3min-1 flow of air, and the TGA (a) and DTG (b) profiles are illustrated in Fig. 3-7. The weight loss up to 100ᵒC (of approximately 5% for both samples) can be attributed to the removal of moisture and light compounds physically absorbed in the spent catalyst. The weight loss (~15 %) between 100 and 300ᵒC, peaked at approx. 170C, may be attributed to the loss of the condensed volatile compounds deposited on the catalyst during the CFP of HL, while the mass loss (3-5%) at 300-800ᵒC may be attributed to the carbon/coke deposition on the catalyst’s surface. Thus, the carbon/coke deposition on the spent catalyst was negligibly low, suggesting high resistance of the zeolite-X catalyst to carbon/coke deposition probably owing to its low surface area (<2 m2/g) and pore volume (<0.01 cm3/g) (Table 3-7). As well known, coke formation on

73 catalyst is strongly dependent on its acidity and textural structure, and generally catalysts with a higher acidity and larger pore volume are more susceptible to carbon/coke deposition at a higher temperature [46–49]. Very interestingly, as shown in Table the BET specific surface area was slightly increased from 1.5 m2/g for the fresh catalyst to 1.8-2.0 m2/g for the spent zeolite X catalysts after the CFP experiments at 450ᵒC and 500ᵒC, with slightly decreased pore size, which might be attributed to the ultrafine particles of the deposited carbon on the catalyst [53].

100 (a) Zeolite-X 450 90 Zeolite-X 500 80

70 Weight (%) Weight

50 0 100 200 300 400 500 600 700 800 Temperature (ᵒC)

0 (b)

-0.004 Zeolite-X 450 Zeolite-X 500 -0.008

-0.012 Deri. Weight (%/min) Weight Deri.

-0.016 0 200 400 600 800 Temperature (ᵒC)

Figure 3-7 TGA (a) and DTG (b) for the coke deposition on the spent zeolite-X.

Table 3-7 Textural properties of the fresh/spent zeolite X catalysts. BET surface area Total pore volume Average pore size Catalyst (m2/g) (cc/g) (nm)

Z-X1 1.5 0.009 12

Z-X 4502 2.0 0.010 11

Z-X 5003 1.8 0.008 9

1 Fresh zeolite X catalyst; 2 Spent zeolite X catalyst after CFP experiment at 450C; 3 Spent zeolite X catalyst after

CFP experiment at 500C.

3.4 Conclusions

In this study, catalytic fast pyrolysis of hydrolysis lignin with/without catalyst (zeolite-X) at various temperatures (400 – 800⁰C) was investigated aiming to produce aromatic fuel and monomeric phenolic chemicals. Some key conclusions from this work are summarized as follows: (1) The use of zeolite-X catalyst in fast pyrolysis of lignin shifted the peak temperature where maximum bio-oil yield was produced from 600ᵒC to 500ᵒC. The presence of the catalyst reduced bio-oil yield slightly from 60% to 56%, accompanied by increased gas yield and char yield, due to catalyzed cracking reactions of the volatile vapor. (2) Catalytic fast pyrolysis of hydrolysis lignin with zeolite-X produced more water in the bio- oils likely due to the hydrodeoxygenation/de-hydration reactions catalyzed by the acidic zeolite-X catalyst. (3) Zeolite-X remarkably increased the yield of monomeric phenolic compounds in the catalytic fast pyrolysis of hydrolysis lignin at all temperatures (400 - 800ᵒC). No significant changes in the catalyst properties (crystallinity, acidity, textural structure) during fast pyrolysis of lignin suggesting superb stability of the catalyst in the process. The high activity and stability of the zeolite-X catalyst might be owing to its strong acidity and low pore volume. (4) The most abundant monomeric phenolics in the lignin-derived bio-oils (irrespective of the presence of catalyst) are guaiacol, syringol, 4-methoxy-3-(methoxymethyl) phenol and metoxyeugenol, at all temperatures, which may be used for production of phenolic resole adhesives or food preservatives. (5) Zeolite X could effectively catalyze cracking of primary of pyrolysis vapors from lignin to form more monomeric phenolics.

3.5 Acknowledgments

The financial support for this work was provided mainly through the NSERC Discovery Program,

NSERC/FPInnovations Industrial Research Chair Program in Forest Biorefinery, and BioFuel Net.

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Chapter 4

4 Zeolite catalysts screening for production of monomer aromatics/phenolics from hydrolysis lignin by catalytic fast pyrolysis

Abstract

In this work, zeolite catalysts, widely used catalysts for effectively cracking of organics into highly deoxygenated and hydrocarbon-rich compounds, were screened for their performance in catalytic fast pyrolysis (CFP) of hydrolysis lignin (HL) in a drop-tube fixed bed reactor at temperatures of 400, 450, and 500ᵒC. Five commercial zeolite catalysts including zeolite X, Zeolite Y (CBV-100, CBV-600, and CBV-780) and ZSM-5 (CBV-8014) were screened, and ZSM-5 exhibited the best performance for converting hydrolysis lignin to monomeric aromatics/phneolics. It was demonstrated that the catalyst total acidity and the Bronsted acid sites play a key role in cracking and deoxygenation of the pyrolysis vapors toward the monomeric aromatic/phneolic hydrocarbons. CFP of HL under the best conditions (450ᵒC, ZSM-5 catalysts), produced bio-oil at 57.4 wt.% yield, and a high yield of monomeric aromatics/phenolics (being 0.11 g/g-HL).

4.1 Introduction

Increasing energy consumption and depleting petroleum resources combined with environmental concerns about greenhouse gas emissions (GHG) are making it vital to find sustainable sources for liquid fuels and chemicals [1,2]. Lignocellulosic biomass is accounted as a promising resource for energy and chemicals owing to its renewability, high carbon content and abundancy. Lignin is a by-product generated in large amount in pulping and cellulosic ethanol industries. Lignin is a natural macro-molecule containing multiple alkylphenol units, which can be converted to aromatics/phenolics for fuels and chemicals through bio-/thermo-chemical conversions. [3].

Fast pyrolysis is a typical thermochemical technology for direct conversion of lignocellulosic biomass into liquid bio-oils for fuels and chemicals, which by far the only industrially realized technology [4]. The foremost technical challenge of fast pyrolysis comes from the lack of commercial application of pyrolysis oils as they are of a lower heating value, only about 50% of that of petroleum, and a pyrolysis oil has poor instability caused by its high oxygen content, high acidity, and hence corrosive. Pyrolysis oils due to these detrimental properties, without expensive upgrading, are unsuitable to be used as a fuel or incorporated into petroleum. Presence of a catalyst in fast pyrolysis, also called catalytic fast pyrolysis (CFP), can produce upgraded bio-oils with a lower oxygen content, lower acidity/corrosivity and higher heating values, etc. Many catalyst have been investigated, including microporous, mesoporous, and macroporous catalysts (ZSM-5, MCM-41, CaO) [5–8]. Generally zeolites have been commonly used as catalysts for CFP of lignocellulosic biomass due to its high acidity or low Si/Al ratios, being effective for cracking of the vapor during the pyrolysis process [9,10].

In a study by Stefanidis et al. [11] different commercial catalysts (zirconia, titania, alumina, zeolite, etc.) were screened in a fixed bed reactor for CFP of wood biomass. Although each catalyst displayed various degrees of catalytic effects, high surface area alumina catalysts with strong Lewis acidity displayed the highest selectivity towards hydrocarbons formation but resulted in a lower yield of oil products, zirconia/titania produced higher yields of oil products than alumina, and ZSM-5 with high surface area displayed moderate selectivity towards hydrocarbons and moderate oil yields. In an another study by Yu et al. [12] CFP of lignin with four different zeolite catalysts of various pore sizes was investigated to determine the role of shape selectivity of

86 zeolites, where it was found that ZSM-5 produced the highest yield of aromatics. Al-MCM-41, Al-MCM-48, HZSM-5 and mesoporous MFI zeolite (ZSM-5) were studied for upgrading the pyrolysis vapor-phase from CFP of miscanthus [13]. In this literature work, it was shown that mesoporous Al-MCM-41 and AL-MCM-48 had better performance in terms of oxygen reduction than the microporous HZSM-5, and mesoporous catalysts can present higher acidity that could assist the removal of oxygenates and the production of phenolics. In another work by Du et al. [14] CFP of microalgae was carried out over various zeolites (H-Y, H-Beta, and HZSM-5). They demonstrated that all the three zeolite catalysts increased the aromatic yields and HZSM-5 was the most effective with the yield 18.13 %. Also, they investigated the effects of Si/Al ratio by using HZSM-5 of 30, 80, and 280 Si/Al ratios. In their research, HZSM-5 with Si/Al ratio of 80 and moderate acidity achieved the best aromatic yield. Their results are inconsistent with that reported by Park et al. [13]. The selectivity of five different ZSM-5 catalysts with different Si/Al ratios (23 – 280) toward production of aromatics was studied by Engtrakul et al. [15], and this study demonstrated that the overall acidity of the catalyst was directly correlated with aromatic yields. Similar results were reported by Zheng et al. [16] in their investigation of CFP of lignin over HZSM-5 of different Si/Al ratios. Whereas, a work by Custodis et al. [17] showed that the selectivity of mesoporous catalysts (Al-MCM-41, Al-SBA-15, and AL-MSU-J) towards to aromatics formation in CFP of lignin was hard to be correlated to solely on acidity of the catalysts. In summary, there are still inconsistent findings on the effects of catalysts acidity on the aromatic products’ selectivity, more comprehensive studies are required to correlating the product yields with the catalysts’ acidity and the type of acid sites.

Low-boiling point aromatic/phenolic compounds that can be potential used for bio-fuels, fuel additives or chemicals. GC-MS serve as a useful instrument to quantitatively analyze the concentrations of low-boiling point aromatics/phenolics, e.g., monomeric aromatics/phenolics from CFP of lignin. The main objective of this work is to screen some commercial zeolite catalysts including zeolite X, Zeolite Y (CBV-100, CBV-600, and CBV-780) and ZSM-5 (CBV-8014) for their performance in CFP of hydrolysis lignin (HL) were screened, and ZSM-5 exhibited the best performance for converting hydrolysis lignin to monomeric aromatics/phneolics measured by GC- MS.

4.2 Materials and methods 4.2.1 Materials

The hydrolysis lignin (HL) used in this study was provided by FPInnovations, and it was the residual from the TMP BioTM process for production of mixed sugars (xylose and fructose) from Aspen wood [18]. The HL is not soluble in common solvent as it contains 50-60 wt% lignin balanced by the residual cellulose and hemicellulose. The molecular weight of the HL could not be based on the ultimate analysis of the HL, it contains 49.76 wt.% carbon, 6.45 wt.% hydrogen, 0.33 wt.% nitrogen, and 43.46 wt.% oxygen (by difference), all on a dry basis. The proximate analysis of the HL (dry basis) was 82.20 wt.% volatile matter, 16.04 wt.% fixed carbon and 1.76 wt.% ash. Four zeolites including ZSM-5 (CBV 8014 in ammonium form) and orthorhombic smmetry and zeolite Y (CBV-100 in sodium form, and CBV-600/CBV-780 in hydrogen form), were all purchased from Zeolyst International (Conshohcken, PA). The zeolite X powder with Si/Al molar ratio of 1.0 and particle size of <45µm was purchased from Sigma-Aldrich (USA) with CSA 1318-02-1, (Zeolite Y and Zeolite-X with cubic/tetrahedral crystal systems). ACS reagent-grade acetone, purchased from Caledon Laboratory Chemicals (ON, Canada), was used as the reactor rising/washing solvent for product separation.

4.2.2 Catalyst characterization

The properties of the five commercial zeolite catalysts are listed later in Table 4-1, in which some characterization properties are obtained from the supplier. In order to prevent losses in the fixed catalyst bed pyrolysis reactor, all zeolite powders were pelletized by pressure pelletizer (about 10 tons), and after crushing, the fraction sieved between 20 and 40 mesh was used for the experiments. The regeneration of the used catalysts was performed by calcining the acetone-washed spent catalysts in a muffle furnace at 450ᵒC in air for 4 h. The crystalline structure of the fresh/spent ZSM-5 catalyst was characterized by X-ray diffraction (XRD) on a Rigaku-MiniFlex powder diffractometer (Woodland, USA), using Cu-Kα (λ = 1.54059 Å) over the 2θ range of 10°-70° with step width of 0.02°. Textural properties of the fresh/spent catalysts were measured by N2 isothermal adsorption at 77 K (NOVA 1200e surface area and pore size analyzer). The specific surface area was calculated using Brunauer-Emmett-Teller (BET) method. Total pore volume was 0 estimated using the volume of N2 gas adsorbed at a relative pressure (P/P ) of 0.99. Density

functional theory (DFT) was used to calculate the pore size distribution based on N2 desorption isotherm.

The total acidity of the zeolite catalysts was measured by NH3-Temperature Program Desorption

(NH3-TPD), carried out on a Quantachrome ChemBET Pulsar TPR/TPD automated chemisorption analyzer. In a typical experiment, about 0.1 g of the sample was pre-treated at 300 °C for 1 h under a flow of helium (99.9%, 120 cm3min-1). After pretreatment, the sample was saturated with anhydrous ammonia at 100°C for 10 min and subsequently flushed with He at the same temperature to remove any physisorbed ammonia. Then, TPD analysis was carried out by heating the sample in helium from ambient temperature to 600°C at 10 °C min-1 and the desorbed ammonia was measured by thermal conductivity detector. The strength of the Bronsted and Lewis acid sites of the zeolites was measured by pyridine FT-IR. A small amount of zeolite (0.2 g) was oven dried at 105˚C for 2hrs. 50 µL of pyridine was added to the catalyst and oven dried at 105˚C for another 2 hrs. Thereafter, 2 mg of catalyst was mixed with 200 mg of KBr and pressed to make a disc. The transparent disc was analyzed by FT-IR using a Perkin Elmer FT-IR spectrometer in the wave number range of 4000 - 500 cm-1 to examine the Bronsted and Lewis acid sites of the catalyst. Moreover, in order to examine the heavy residual oil and coke deposition on the spent catalysts, thermogravimetric analysis (TGA) was performed on a PerkinElmer Pyris 1 TGA by heating the spent catalyst in 20 cm3min-1 flow of air from 40C to 800C at 10 Cmin-1.

4.2.3 Experimental setup

Catalytic fast pyrolysis (CFP) experiments were carried out in a drop-tube/fixed bed reactor made of SS 316L tube (3/4 inch O.D., 26.5 inch length). The photo of the setup is shown in Fig. 4-1. The reactor was heated in an electric furnace whose temperature was controlled by a temperature controller. The furnace temperature could be varied from 200 to 1200 ᵒC. The flow rate of nitrogen gas, flowing downward through the biomass feeder and the reactor, was set and controlled with a mass flow controller meter (Brokenhorst High-Tech EL-FLOW). The temperature controller and mass flow controller meter were pre-calibrated and all the temperatures and gas flow rate are the actual values inside the reactor during the experiments, temperature was calibrated by putting a thermocouple on top of the catalyst bed.

CFP of HL was carried out at temperatures ranging 400, 450, and 500ᵒC with sweeping N2 gas at a flow rate of 97 cm3min-1. In a typical run, 2 g of feedstock was loaded into the feeder (1-inch OD tube) above the reactor separated from the reactor by a ball valve, and 0.4 g of quartz wool was put in the bottom of the reactor as a support for the catalyst-bed of 2 g of catalyst in the tubular reactor positioned in the hot-zone of the furnace, as illustrated in Fig. 4-1. Then 0.4 g of quartz wool was loaded on the top of the catalyst-bed to separate the HL and pyrolysis char from the catalyst-bed. Before starting the experiment, the reactor and the feeder were vacuumed/purged thrice repeatedly to eliminate air inside the reactor system, and leak proof was ensured by pressurizing the reactor system with high pressure nitrogen gas before each experiment. The 3 -1 reactor was then heated up to the desired temperature at 10-20°C/min in 97 cm min flow of N2. After the reactor temperature reached to the specified temperature, the HL particles in the feeder was fed into the reactor rapidly by opening the ball valve. Assuming negligible change in total gas 3 -1 flow rate (97 cm min N2) during the pyrolysis experiments, the heating rate for the HL feed in the reactor was estimated to be > 750 C/s (according to gravitational and N2 pressure force to send the particles down), and the residence time of the vapor inside the 2 g catalyst bed with about 0.8 cm3 volume, was thus estimated to be < 0.5 s. The vapor product was condensed into a liquid product in a condensation trap refrigerated at −6°C. The non-condensable gaseous products were collected using a gas bag for 20 min after feeding the HL. Once being cooled to room temperature, the reactor system including the tubular reactor and the condensation trap was washed with 150 ml of acetone for recovery of all liquid products (i.e., bio-oil).

Figure 4-1 The catalytic fast pyrolysis reactor.

4.2.4 Product Separation

When the reactor was cooled down to room temperature, it was opened and the whole reactor system was rinsed with 150 ml of reagent grade acetone to completely remove bio-oil from the inner reactor walls, the solid residue (char) and catalyst bed, as well as the condensation trap. The rinsing acetone was removed by evaporation under reduced pressure in a rotary evaporator at 45ᵒC, and the product was weighed and designated as pyrolysis oil or simply bio-oil. It should be noted that small amounts of bio-oil samples were collected before evaporation of acetone for GC-MS analysis, and the results were compared with bio-oil after the evaporation while no significant changes were observed. The char residue and spent catalyst were collected separately and oven

91 dried at 105ᵒC for an hour to a constant weight to determine char yield, and to recover the spent catalyst. The gas samples collected in the gas bag was analyzed by micro-GC to determine the gas compositions and yields.

4.2.5 Product characterization

The gas samples were analyzed by GC-TCD (Agilent 3000 Micro-GC) equipped with dual columns (Molecular sieve and PLOT-Q) and thermal conductivity detectors and the GC system to detect gas species up to C3, which are oxygen, nitrogen, hydrogen, carbon monoxide, carbon dioxide, methane, ethylene, ethane, propene, and propane. Elemental analysis of the HL feedstock, bio-oils and chars was performed with an elemental analyzer (CHNS-O Analyzer FLASHEA 1112 SERIES, Thermo Scientific), and their higher heating values (HHVs) were calculated based on the Dulong’s formula [19]. The water content of bio-oil was determined by Karl-Fisher titration method using a Mettler Toledo DL32 colorimetric titrator. The viscosity and pH values of bio- oils were measured with a viscosity meter (CAP 2000+ Viscometer, Brookfield) and pH meter (ORION 2STAR PHBenchtop, Thermo Scientific), respectively.

The volatile compositions bio-oil products were quantitatively analyzed with a gas chromatograph- mass spectrometer [GC-MS, Agilent Technologies, 5977A MSD) with a SHRXI -5MS column (30 m × 250 mm × 0.25 mm) and a temperature program of 60ᵒC (hold for 2 min) → 120ᵒC (10 ᵒC/min) → 280ᵒC (8 ᵒC /min, hold for 5 min)]. Compounds in the oil were identified by means of the NIST Library with 2011 Update and the concentrations of the low boiling point volatile compounds (including the target monomeric aromatics) in the bio-oil samples were determined using di-n-butyl ether (Alfa Aesar) as an internal standard. Molecular weight distributions of the bio-oils were measured by Waters Breeze GPC-HPLC instrument equipped UV detector using styragel HR 1 as the analytical column at 40°C using 1 cm3min-1 THF as the mobile phase. Polystyrene narrow standards were used for calibration of the GPC-UV.

4.3 Results and discussion

4.3.1 Fresh catalysts characterization

Table 4-1 lists some properties of the 5 commercial zeolite catalysts used in this study. The

SiO2/Al2O3 Mole Ratio ranges from 1.0 (Zeolite X) to 5.1-5.2 for CBV 100 (Zeolite Y) and CBV 600 (Zeolite Y), and to 80 for CBV 780 (Zeolite Y) and CBV 8014 (ZSM-5). These five zeolites have different cation forms including sodium form for Zeolite X and zeolite Y (CBV-100), hydrogen form for Zeolite Y (CBV-600/CBV-780) and ammonium form for ZSM-5 (CBV 8014). The three Zeolites Y and ZSM-5 have a higher BET surface area (425 m2/g) with a relatively large pore volume and microporous structure (e.g., 0.25 cm3/g total pore volume and 1.3 nm average pore size for ZSM-5). In contrast, the Zeolite X has a much lower total pore volume (0.01 cm3/g) but with a large average pore size (12 nm).

Table 4-1 The properties of the 5 commercial zeolite catalysts.

Unit Total Average SiO2/Al2O3 Na2O Surface Cell pore, pore Mole Cation Form Weight Area, Size, cm3/g size, nm Catalyst Ratio % m2/g nm

Zeolite X 1.0 Sodium n.a1 n.a. 1.5 0.01 12

CBV 100 5.1 Sodium 13 2.47 900 n.a n.a (Zeolite Y)

CBV 600 5.2 Hydrogen 0.2 2.44 660 n.a n.a (Zeolite Y)

CBV 780 80 Hydrogen 0.03 2.42 780 n.a n.a (Zeolite Y)

CBV 8014 80 Ammonium 0.05 n.a. 425 0.25 1.3 (ZSM-5)

1Not analyzed or not available.

Fig. 4-2 presents the pyridine FT-IR spectra of Zeolite-X, CBV-100, CBV-600, CBV-780, and CBV-8014 zeolite catalysts. Pyridine produces a band at around 1545 cm-1 when adsorbed on Bronsted acid sites, a band at around 1450 cm-1 when adsorbed on Lewis acid sites, and a band around 1490 cm-1 when adsorbed on Lewis and Bronsted acid sites [20]. Thus, as shown in Fig. 4-2, the Zeolite Y (CBV-100) has the lowest Bronsted acid peaks, while ZSM-5 (CBV-8014) has the highest Bronsted acidity peaks at 1545 cm-1 and 1490 cm-1, although it has the moderate total acidity (0.91 mmol/g) among all Zeolites tested (Table 5-4), and Zeolite-X with highest total acidity (1.16 mmol/g) between selected zeolite catalysts shows moderate range Bronsted acidity peaks. Therefore, the existence of the high Bronsted acid sites in the catalyst framework of ZSM- 5 (CBV-8014) or high total acidity may lead to its unique performance in the CFP of HL, as discussed later.

Figure 4-2 Pyridine FT-IR spectra of the Zeolite-X, CBV-100, CBV-600, CBV-780, and CBV-8014 zeolite catalysts.

4.3.2 Effect of catalyst type on product yields

Fast pyrolysis or CFP of HL was performed at temperatures of 400, 450, and 500ᵒC without or with various Zeolite catalysts (with varying Si/Al ratios): Zeolite X (Si/Al = 1), CBV-100 (5), CBV-600 (5), CBV-780 (80), and CBV-8014 (80). CFP products yields are presented in Fig. 4-3. Generally, when increasing temperature, the bio-oil and gas yields increased, accompanied by a decrease in char yield, irrespectively of the presence of catalyst. Increase in operation temperature promotes the cracking reactions and hence results in more gas production [22,23]. The presence of Zeolite X and CBV-100 catalysts resulted in reduction of bio-oil yield, likely due to the strong total acidity of these two catalysts (1.1-1.2 mmol/g determined by NH3-TPD, and presented in Table 5-4). Generally, in biomass CFP, the presence of catalyst with a high acidity would catalyze vapor cracking reactions, producing less oil and more gas products [24]. It should be noted that the mass balance in these operations without catalyst and with the Zeolite X and CBV-100 catalysts was in the range of 90-95 wt%, suggesting a mass loss of 5-10 wt%, which could be due to the formation of heavy organics or coke deposited in the glass wool/catalysts.

On the other hand, with the other three Zeolites, two Zeolite Y (CBV-600, CBV-780) and the ZSM-5, the presence of catalyst led to a significantly increased oil yield, slight increase in gas yield and essentially no change in char yields. These results may be explained below. As commonly known, a CFP process could be divided into two stages: Stage-1 the primary pyrolysis process (devolatilzation) in which gas, primary organic vapors and char is produced via thermal pyrolysis. At this stage, feedstock compositions, temperature and heating rate are the dominant factors for determination of the product yields. Stage-2 Catalytic cracking of the primary organic vapors into light vapors on the active sites of the catalyst. At this stage several reactions would occur, such as deoxygenation, aromatization, cracking to form H2O, CO2, CO, alkanes, alkenes and polymerizations/condensation to form heavy organics/coke [21].As such, the yield of char formed exclusively in Stage-1 should be essentially unaffected by the presence of a catalyst, which explained the result above that the char yield is essentially independent of the use of catalyst. In contrary, the presence of a catalyst would influence the primary organic vapor reactions in Stage- 2, where the catalysts (in particular CBV-600, CBV-780 and ZSM-5, all with strong Bronsted sites) would catalyze the deoxygenation/aromatization reactions [5], enhance cracking reactions to form lower Mw compounds, and prevent polymerizations/condensation, resulting in less formation of heavy organics/coke, as evidenced by the improved mass balance (95-99 wt%). .

None Zeolite-X CBV-100 CBV-600 CBV-780 CBV-8014 Bio-oil Gas Char 100

40 Yield (wt.%) Yield

- 400 450 500 400 450 500 400 450 500 400 450 500 400 450 500 400 450 500 Temperature (˚C)

Figure 4-3 Products yields in catalytic fast pyrolysis of hydrolysis lignin at various temperatures without or with various Zeolite catalysts.

4.3.3 Effects of catalyst on physical properties and elemental compositions of bio-oil

The physical properties and elemental composition of the obtained bio-oils with/without catalyst are given in Table 4-2. Generally speaking, the use of catalyst led to enhanced oil quality in terms of increased pH value and reduced molecular weight. The pH was increased from 4.32 without catalyst to 4.90-5.90 in the presence of catalyst due to hydrodeoxygenation reaction to remove the carboxylic groups and hence the acidity of the oil. The Mw decreased from 230 g/mol without catalyst to 120-214 g/mol with catalyst (except for Zeolite X) as a result of enhance cracking of the pyrolytic vapors on the catalyst surface. However, the water content of the oil increased by the presence of a catalyst most likely due to hydrodeoxygenation/de-hydration reactions by the acidic catalysts.

The presence of all Zeolite Y catalysts (CBV-780, 100, and 600) reduced the heating value of the oil from 17.4 MJ/kg without catalyst to 14.6, 12.7, and 8.6 MJ/kg, respectively. In contrast, the use of Zeolite X or ZSM-5 (CBV-8014) produced oil with much higher carbon and lower oxygen contents or much lower O/C ratio and hence a much higher heating value, being 21.5 MJ/kg and 23.7 MJ/kg, respectively. These results revealed that existence of a catalyst with either high total acidity (Zeolite X) or more Bronsed acid sites (ZSM-5) could promote hydrodeoxygenation reactions on the acidic sites of the catalyst leading to oil products with a greater heating value [25].

Table 4-2 Physical properties of bio-oils at 450 ᵒC. Catalyst 1 1 2 4 Mn Mw Pd pH Viscosity Water Elemental composition HHV O/C H/C (g/mol) (g/mol) (cP) content (% d.b.) (MJ/kg) (-) (-) (wt.%) C H N O3

None 153 230 1.5 4.3 7.1 8.1 47.1 6.7 0.4 45.8 17.4 0.7 1.7

Zeolite X 170 265 1.5 4.9 4.7 14.5 54.9 6.8 0.5 37.8 21.5 0.5 1.5

CBV-100 (Zeolite Y) 101 149 1.3 5.6 8.8 39.9 45.8 4.2 0.2 49.7 12.7 0.8 1.1

CBV-600 (Zeolite Y) 93 120 1.3 5.9 9.8 28.4 40.9 3.1 0.2 55.7 8.4 1.0 0.9

CBV-780 (Zeolite Y) 109 150 1.4 5.7 8.4 23.1 50.7 3.8 0.3 45.1 14.6 0.7 0.9

CBV-8014 (ZSM-5) 140 214 1.5 5.6 9.6 32.3 62.6 5.7 0.5 31.2 23.7 0.4 1.1

1 2 3 Mn and Mw are the number-average and weight-average molecular weights determined by GPC-UV; Measured at 50 ᵒC; By difference and assuming negligible

sulfur and ash contents; 4Calculated by Dulong formula HHV (MJ/ kg) = 0.3383C + 1.422 (H - O/8).

4.3.4 Gas analysis

The gas products from fast pyrolysis of HL without and with various catalysts at different temperatures, compared with those from the blank tests without catalyst, were analyzed by GC- TCD and the results of the analysis (presented in volume %) are shown in Table 4-3. As clearly shown and expected, increasing reaction temperature or the presence of the Zeolite catalysts

produced more CO/CO2 gases, due to the enhanced thermal cracking reactions and the deoxygenation reactions of the pyrolytic vapor catalyzed by the acidic Zeolites catalysts [11,26,27].

Interestingly, the formation of H2 and CH4, though increased with increasing temperature as expected due to the enhanced cracking of H-C and C-C bonds of the feed in Stage 1 of the pyrolysis

process, the presence of all Zeolite catalysts decreased the formation of H2 and CH4, which might

be owing to the in-situ catalytic reforming of CH4 to form CO and H2 and the in-situ consumption

of the H2 by the de-oxygenation reactions. More research in this regard is needed and interesting.

Table 4-3 Effect of catalysts on gas composition (vol.%) from fast pyrolysis of HL without and with various catalysts at different temperatures.

Catalyst Temp.(ᵒC) H₂ CH₄ CO₂

Blank 400 1.1±0.0 17.0±0.0 1.2±0.0 78.8±1.4

Blank 450 2.3±0.0 18.6±0.1 1.2±0.0 76.0±0.7

Blank 500 5.7±0.1 23.7±0.0 69.0±1.2 Zeolite X 400 1.1±0.0 19.2±0.0 1.1±0.0 76.8±0.0

Zeolite X 450 3.4±0.0 23.5±0.0 1.5±0.0 70.0±0.0

Zeolite X 500 5.0±0.0 24.6±0.0 2.3±0.0 66.3±0.0

CBV100 400 0.1±0.0 0.6±0.0 39.1±0.3 6.0±0.0 52.4±0.4 CBV100 450 0.2±0.0 0.7±0.0 44.6±0.7 7.6±0.7 0.2±0.0 44.8±0.1

CBV100 500 0.2±0.0 1.1±0.0 41.9±0.4 13.0±0.0 0.2±0.0 41.8±0.5

CBV600 400 0.4±0.0 44.2±0.2 4.3±0.0 0.2±0.0 48.9±0.2

100

CBV600 450 0.1±0.0 0.5±0.0 43.2±0.5 9.2±0.3 0.1±0.0 45.7±0.6

CBV600 500 0.5±0.0 0.9±0.0 39.6±0.5 12.8±0.4 44.5±0.1

CBV780 400 0.1±0.0 1.1±0.0 12.8±0.0 13.2±0.3 71.1±0.2

CBV780 450 0.5±0.0 2.0±0.1 15.0±0.5 14.0±0.0 66.7±0.6

CBV780 500 1.7±0.1 3.0±0.2 13.1±0.5 15.6±0.0 64.6±0.4

CBV8014 400 1.5±0.0 4.3±0.0 42.5±0.6 32.0±1.5 11.6±0.2

CBV8014 450 2.7±0.2 4.8±0.4 45.1±1.3 33.2±2.7 12.1±0.4

CBV8014 500 2.8±0.0 5.1±0.1 45.2±0.6 34.2±2.8 12.3±0.3

4.3.5 Bio oil chemical compositions

The produced bio-oil products were analyzed quantitively by GC-MS (pre-calibrated with pure compound of di-n-butyl ether as an internal standard) for their compositions and yields of low boiling points compounds. The yields of total monomeric aromatics/phenolics in fast pyrolysis of HL without/with zeolite catalysts at different temperatures are shown in Fig. 4-4. It should be noted that pyrolysis bio-oils have very complex composition, with more than 400 compounds of lower boiling points detectable by GC-MS [28], and many high-boiling point heavy compounds not detectable by GC-MS due to the limitations of the GC method (which is valid only for low boiling-point volatile compounds). In general, only about 10-40 wt.% of mass of a pyrolysis is measurable by GC-MS [29,30]. In all bio-oil samples analyzed in this study, the major volatile aromatic compounds detected and quantified are: benzene, toluene, C8 aromatics (including p-/o- xylene, ethylbenzene), C9-C11 aromatics (including C3-C5 alkyl derivatives of benzene), naphthalene (including naphthalene and its alkyl derivatives), eugenol, and syringol phenols (including phenol and 4-methyl-phenol), cresol, xylenols, eugenol, metoxyeugenol, and syringol. In the experiments without catalyst, as shown in Fig. 4-4, monomeric aromatics yield was 67.43 mg/g of hydrolysis lignin, and the major detected compounds include phenols (phenol, 3-methyl- phenol, 2,6-dimoxy-phenol), guaiacols (guaiacol and ethylguaiacol, 4-vinylguaiacol), eugenols (eugenol, iso-eugenol, trans-isoeugenol, metoxyeugenol), 3-metoxycatechol, syringol, 3-

101 metoxybenzene, syrinaldehyde, acetosyringone. Surprisingly, the use of two Zeolite Y catalysts (CBV-780 and CBV-100) decreased the yield of monomeric aromatics/phenolics, perhaps due to the yield of more compounds with higher boiling points due to the presence of less Bronsted acid sites or the relatively lower total acidity of these two Zeolite Y catalysts. Interestingly, the catalytic cracking of HL over one Zeolite Y (CBV-600) and ZSM-5 (CBV-8014) drastically increased the yield of total monomeric aromatics/phenolics (mainly xylene, methyl toluene, trimethyl benzene, phenol and other phenolic compounds) to up to about 0.11 g/g of HL at 450C with the ZSM-5 catalyst, compared with 0.07 g/g of HL without catalyst. This result can also be evidenced by the elemental analysis of the bio-oils (Table 4-2) where the H/C of the oil decreases from 1.7 without catalyst to 1.1 with the ZSM-5 catalyst. Therefore, the existence of the high Bronsted acid sites (Fig. 4-2) in the catalyst framework of ZSM-5 (CBV-8014) may account for its unique performance in the CFP of HL, promoting the deoxygenation reactions of the oil vapor to produce more monomeric aromatics (Fig. 4-4).

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None Zeolite X CBV-100 CBV-600 CBV-780 CBV-8014 0.12 0.11 0.10 0.09 0.08 0.07 0.06 0.05 0.04 0.03 0.02 0.01

Total monomeric aromatics/phenolics HL of g/g aromatics/phenolics monomeric Total - 400 450 500 Temperature (ᵒC)

Figure 4-4 Yields of total monomeric aromatics/phenolics in fast pyrolysis of HL without/with zeolite catalysts at different temperatures.

4.3.6 Spent catalysts characterization

4.3.6.1 Catalyst crystalline structure

The crystalline structure of both fresh and spent catalyst of ZSM-5 (CBV 8014) after the 450ᵒC experiment were characterized by X-ray diffraction (XRD), as illustrated in Fig. 4-5. As clearly shown in the Figure, the XRD pattern of ZSM-5 catalyst for the fresh and spent reveals strong XRD lines (of which the strongest lines are at 2Ѳ=23.30ᵒ) ascribed to the typical crystallographic planes of zeolite. The above XRD results indicate that the ZSM-5 catalyst (CBV 8014) has outstanding thermal stability during the CFP operations, as similarly reported in some literature work using ZSM-5 zeolite catalysts [31,32].

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Spent XRD Intensity (a.u.) XRD Intensity

Fresh

10 20 30 40 50 60 70 2ɵ (Cu Kα)

Figure 4-5 The XRD patterns of the fresh and spent catalyst of ZSM-5 (CBV 8014) after the 450 ᵒC experiment [31].

4.3.6.2 Catalysts total acidity analysis

The NH3-TPD profiles of all five Zeolite catalysts in fresh/spent/regenerated states are shown in Fig. 4-6. The total acidity values of all five Zeolite catalysts in fresh/spent/regenerated states are summarized in Table 4-4. As shown in the NH3-TPD profiles, all of the fresh catalysts display profiles with two NH3-desorption peaks at around 180-220ᵒC and 400-500ᵒC, which are often ascribed to the weak and strong acid sites, respectively. From Fig. 4-6, it can be seen that when compared with the corresponding fresh catalysts, all spent zeolite catalysts have a lower peak intensity and area on both strong and weak acid sites, suggesting that the amounts of strong acid (Bronsted acid) and weak acid (Lewis acid) sites were reduced during CFP of HL at 450C, as

104 similarly observed in the literature [33,34]. As shown in Fig. 4-6 and Table 4-4, the total acidity (mmol/g) values of these Zeolite catalysts can be recovered after regeneration of the spent catalysts. Interesting however, the NH3-TPD profile of the spent CBV-780 catalyst is very different from any others, as the TPD signals keeps increasing after around 400 ᵒC, rather than peaks at around 600C for all other spent catalysts. This difference should be discussed. First of all, CBV- 780 catalyst has the lowest acidity among all Zeolites tested (Table 5-4) which also account for the lowest yield of monomeric aromatics/phenolics in CFP of HL (Fig. 4-4). A possible explanation for the unusual continuously increased NH3-TPD signals from the spent CBV-780 after 400ᵒC might be due to desorption/decomposition of some heavy organics deposited on the catalyst during CFP of HL, and the continuously evolved organic gas/vapor upon heating during the NH3-TPD measurement could be detected as TPD signals by the thermal conductivity detector (TCD).

9 8 Zeolite-X 7 Zeolite-X 450 6 R-Zeolite-X 450 5 4

3 TCD Signal (mV) Signal TCD 2 1 0 100 200 300 400 500 600 Temperature (ᵒC)

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7 Fresh CBV-100 6 Reg CBV-100 5 Spent CBV-100 4 3

2 TCD Signal (mV) Signal TCD 1 0 100 200 300 400 500 600 Temperature (ᵒC)

3 Fresh CBV-600 2.5 Reg CBV-600 Spent CBV-600 2

1.5

1 TCD Signal (mV) Signal TCD 0.5

0 100 200 300 400 500 600 Temperature (ᵒC)

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4 Fresh CBV-780 3.5 Reg CBV-780 3 Spent CBV-780 2.5 2 1.5

TCD Signal (mV) Signal TCD 1 0.5 0 100 200 300 400 500 600 Temperature (ᵒC)

1.8 Fresh CBV-8014 1.6 Spent CBV-8014 1.4 Reg-CBV-8014 1.2 1 0.8 0.6 TCD Signal (mV) Signal TCD 0.4 0.2 0 100 200 300 400 500 600 Temperature (ᵒC)

Figure 4-6 NH3-TPD profiles of all five Zeolite catalysts in fresh/spent/regenerated states.

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Table 4-4 Total acidity values of all five Zeolite catalysts in fresh/spent/regenerated states.

Catalyst Total acidity (mmol/g)

Fresh Spent1 Regenerated

Zeolite X 1.16 1.27 2.01

CBV-100 (Zeolite Y) 1.11 1.03 1.08

CBV-600 (Zeolite Y) 1.01 0.68 0.79

CBV-780 (Zeolite Y) 0.42 2.352 0.25

CBV-8014 (ZSM-5) 0.91 0.34 0.46

1After 450ᵒC experiments; 2 This value is not likely the true value due to the interference of the evolved vapor by decomposition of the heavy organics deposited on the spent catalyst of CBV- 780.

To validate the above explanation, TGA-FTIR analysis was performed by heating the spent catalyst of CBV-780 and the spent catalyst of CBV-8014 (for comparison) in 20 cm3min-1flow of

-1 N2 from 40C to 600C at 10 Cmin where the gas/vapor evolved during the heating was online measured by FT-IR in the wave number range of 3700 - 700 cm-1 in each 20ᵒC from 340 to 600ᵒC. Fig. 4-7 presents the TGA-FTIR spectra of the evolved gas/vapour from spent catalysts of CBV-

780 and CBV-8014 when heated from 340 to 600ᵒC in N2.

As shown in Fig. 4-7a, many IR absorbance bands were detected while heating the spent catalyst of CBV-780, indicating the evolution of various gas/vapor from the spent catalyst sample when heated at elevated temperatures. The bands between 1500 to 1550 cm-1 are attributed to the bending -1 peaks of methyl (-CH3) and methylene (-CH2-) groups. The absorption peaks at 1650 cm may be attributed to C=O stretching vibration of carbonyl groups of ketones, aldehydes, and carboxylic acids. The absorbance at 2181 cm-1 of C-O stretching suggests the CO evolved from the spent CBV-780, formed by cracking and reforming of the oxygenated organics. The IR bands at 2375 -1 cm are attributed to the stretching vibration of C=O suggesting the emission of CO2, released by

108 de-oxygenation/cracking/reforming of the oxygenated organics. The broad absorption at 3273 cm- 1 is typical of O-H stretching suggesting the emission of phenolics, alcohols, carboxylic acids or pyrolysis water [35–37]. In contrary, the TGA-FTIR spectra from the heated spent catalyst of CBV-8014, almost no IR absorbance band was detectable, suggesting negligible deposition of heavy organics in the ZSM-5 catalyst during the CFP of HL. Therefore, the unusual continuously increased NH3-TPD signals from the spent CBV-780 after 400ᵒC (Fig. 4-6) can be explained by the continuously evolution of organic gas/vapor from the spent CBV-780 detected as TPD signals by the thermal conductivity detector (TCD) during the NH3-TPD measurement.

109

3273 (a) 1550 2181 1650 2375 600 ᵒC

580 ᵒC

560 ᵒC

540 ᵒC

520 ᵒC

500 ᵒC

480 ᵒC

460 ᵒC Absorbance (a.u.) Absorbance 440 ᵒC

420 ᵒC

400 ᵒC

380 ᵒC

360 ᵒC

340 ᵒC

700 1200 1700 2200 2700 3200 3700 Wave nmber (cm⁻¹)

110

(b) 600 ᵒC

580 ᵒC

560 ᵒC

540 ᵒC

520 ᵒC

500 ᵒC

480 ᵒC

460 ᵒC

440 ᵒC Absorbance (a.u.) Absorbance 420 ᵒC

400 ᵒC

380 ᵒC

360 ᵒC

340 ᵒC

700 1200 1700 2200 2700 3200 3700 Wave number (cm⁻¹)

Figure 4-7 TGA-FTIR spectra of the evolved gas/vapour from spent catalysts of CBV-780

(a) and CBV-8014 (b) when heated from 340 to 600 ᵒC in N2.

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4.3.6.3 Carbon/coke deposition on the catalysts

One of the major issues of CFP process is the formation and deposition of coke/carbon (retaining of carbonaceous deposits) on the catalyst surface, which could deactivate the catalyst by poisoning the acid sites and blocking pores of the zeolite catalyst. In order to examine the extent of carbon/coke deposition during the CFP of HL in this study, thermogravimetric analysis (TGA) and differential thermogravimetric (DTG) measurements were conducted on two selected spent catalysts of CBV-780 (the worst catalyst in terms of the yield of monomeric aromatics/phenolics) and CBV-8014 (the best catalyst) after 450ᵒC experiments. The TGA tests on these two spent catalysts were operated in air at a heating rate of 10 ᵒCmin-1 and the profiles are demonstrated in Fig. 4-8. The weight loss up to 100ᵒC (of approximately 2 wt.% for both samples) is due to the removal of moisture and light compounds physically adsorbed on the spent catalyst. The weight loss (~10 wt.% in CBV-8014 and 18 wt.% in CBV-780) between 100ᵒC and 600ᵒC, may be attributed to the combustion loss of the heavy organics (acetone insoluble) deposited on the catalyst during the CFP of HL, while the mass loss (1-1.5 wt.% for both) at 600-800ᵒC may be attributed to the coke or fixed carbon on the catalyst’s surface. In addition to TG, differential thermogravimetric curves (DTG, in wt.%/min) show that the mass loss peaks at 95C and 550C, representing the removal of moisture and acetone insoluble heavy organics deposited on the spent catalyst for both catalysts. The above results suggest that coke deposition on both Zeolite catalysts are negligible owing to high BET surface areas (>425 cm2/g) and microporous pore structure (e.g., 1.31 nm for the ZSM-5) for both fresh catalysts, as given previously in Table 4-1. However, the amount of heavy organics deposited on the spent Zeolite catalysts was relatively high, which could account for the decreased acidity (Table 4-4) and specific surface area/total pore volume of the spent catalysts (Table 4-5).

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100 1.5 ~10% 90 TGA 1 80

70 0.5

60 DTG 0 Weight (%) Weight 50

-0.5 (%/min) Weight Drei. 40 (a) 30 -1 0 100 200 300 400 500 600 700 800 Temperature (ᵒC)

100 1.5

90 ~18% 1 TGA 80

70 0.5

DTG

60 0 Weight (%) Weight 50

-0.5 (%/min) Weight Drei. 40 (b) 30 -1 0 100 200 300 400 500 600 700 800 Temperature (ᵒC)

Figure 4-8 TGA/DTG profiles of the spent catalysts of CBV-8014 (a) and spent CBV-780

(b) heated from 25˚C to 800 ˚C in N2.

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Textural properties of the fresh, spent, and regenerated catalyst of the ZSM-5 (CBV-8014) were measured and are compared in Table 4-5. It is clear that the surface area and total pore volume of the fresh catalyst (379.63 m2/g and 0.248 cm3/g) were decreased to 219.56 m2/g and 0.164 cm3/g, respectively, after the CFP experiment. However, the textural properties of the spent catalyst after regeneration restore to almost the same as those of the fresh catalyst, suggesting a good potential of recycling the catalyst in industrial applications.

Table 4-5 Textural properties of the fresh, spent, and regenerate CBV-8014.

Average Catalyst BET surface Total pore pore size area (m2/g) volume (cc/g) (nm)

CBV-8014 (Fresh) 379.63 0.248 1.31

CBV-8014 (Spent) 219.56 0.164 1.49

CBV-8014 (Regenerate) 377.76 0.277 1.47

4.4 Conclusion

In this study, performance of five different zeolite catalysts: Zeolite X, Zeolite Y (CBV-100, CBV- 600, and CBV-780) and ZSM-5 (CBV-8014) in catalytic fast pyrolysis (CHP) of hydrolysis lignin (HL) was compared at various temperatures (400, 450, and 500ᵒC) aiming to produce monomeric aromatics/phenolics. Some key conclusions from this work are summarized as following: (1) Existence of a Zeolite catalyst with either high total acidity (Zeolite X) or more Bronsted acid sites (ZSM-5) could promote hydrodeoxygenation reactions on the acidic sites of the catalyst leading to oil products with a greater heating value. (2) Zeolite Y (CBV-600) and ZSM-5 (CBV-8014) are most effective catalysts for promoting the yield of total monomeric aromatics/phenolics in CFP of HL. The highest yield of monomeric aromatic/phenolic compounds (0.11 g/g of HL) was obtained by CFP of HL with ZSM-5 (CBV-8014) catalyst owing to its more Bronsted acid sites. (3) During the CFP operations, no significant change in the ZSM-5 catalyst’s crystalline structure, while the catalyst’s total acidity and specific surface area/porosity decreased due

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to the deposition of heavy organics on the spent Zeolite catalysts. However, all these properties could restore to those of the refresh catalyst, suggesting a good potential of recycling the catalyst in industrial applications.

4.5 Acknowledgments

The financial support for this work was provided mainly through the NSERC Discovery Program, NSERC/FPInnovations Industrial Research Chair Program in Forest Biorefinery, and BioFuel Net.

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Chapter 5

5 Improving activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis

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Abstract:

This work aimed to further enhance the activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis. To this end, various treatment approaches including acidification with H2SO4 and H3PO4 and metal (Ni) loading were performed on the ZSM-5 zeolite. Catalytic fast pyrolysis (CFP) of hydrolysis lignin (HL) was conducted at 450ᵒC using ZSM-5 zeolites with various strengths of acidity (ZSM-5 and

Ni-ZSM-5 with moderate Lewis and Bronsted sites, H2SO4-ZSM-5 and H3PO4-ZSM-5 with more Bronsted sites). The results show that the yield of monomeric aromatic compounds increased considerably by increasing the Bronsted acid site and total acidity of the catalyst. With the best catalyst, H2SO4-ZSM-5, the total monomeric aromatics/phenolics yield increased to 151 mg/g-HL, compared to 68 mg/g-HL without catalyst, 84 mg/g-HL with ZSM-5, 96 mg/g-HL with H3PO4-

ZSM-5, and 85 mg/g-HL with Ni-ZSM-5. The H2SO4-ZSM-5 demonstrated to be thermally stable and has superb resistance to carbon/coke deposition, owing to its microporous structure, relative large BET surface area and presence of strong Bronsted acid sites.

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5.1 Introduction:

The fundamental requirements of developing biorefining technologies for transforming raw biomass into chemicals and fuels is the processing cost, efficiency and quality/values of the produces, which are all related to the development of inexpensive and effective catalysts. For example, fast pyrolysis though being the industrially realized biomass conversion technology is limited by the poor quality of pyrolysis bio-oil, consisting of hundreds of oxygenated organic compounds that are corrosive, instable and with a poor heating value [1]. Catalytic fast pyrolysis (CFP) has demonstrated to be cost-effective approach to improving the overall quality of the bio- oil through the catalytic cracking and de-oxygenation of pyrolysis vapor phase to low molecular weight bio-oil products with reduced oxygen content (and hence better quality for both fuel and chemical applications) [2,3].

Solid acid catalysts such as alumina and aluminosilicate zeolites (e.g., ZSM-5, Zeolite Y, Zeolite X) have widely used for CFP of biomass for producing high-quality bio-oils, owing to their unique chemical and structural properties (acidity, high surface area, and porous structure, etc.), although the application of solid acid catalysts in CFP of biomass has some challenges related to active sites poisoning and variations in the pore structure of the catalyst by coke/carbon deposition [4]. Compared with the alumina-based catalysts, zeolite catalysts perform well in terms of its Bronsted acidity and stability, both of which are important factors in CFP of lignocellulosic biomass for production of bio-oils. Different types of zeolites with variation in the Si/Al ratio would greatly affect the overall structure (such as surface area/porosity, acidity and acid strength, type of acid sites - Bronsted/Lewis sites, etc.) [5,6]. Ma et al. [7] showed that with increasing Si/Al ratio, the total acidity and the number of Bronsted acid sites on the zeolite catalyst decreased. In the work by Du et al. [8], effects of different Si/Al ratios of zeolite catalyst were investigated with respect to the yield of aromatic hydrocarbons in catalytic pyrolysis of microalgae, where three HZSM-5 catalysts with varied Si/Al ratios (30, 80, and 280) was compared, and it was shown that by increasing Si/Al ratio the aromatics yield decreased. It was also shown that the maximum yield of aromatics was achieved with HZSM-5 at Si/Al ratio of 80, which provides moderate acidity to achieve high aromatics production and reduce the coke formation in the process. In a work by Engtrakul et al. [1], effect of ZSM-5 acidity on aromatic product selectivity during upgrading of

122 pine pyrolysis vapor was investigated. They showed that by increasing acid site concentration, the formation rate of aromatic and cyclization products increased. In a work by Zheng et al. [9], effects of acidity of HZSM-5 catalyst on yield and selectivity of aromatics during catalytic upgrading of biomass pyrolysis vapor were examined. They showed that increasing total acidity of the zeolite catalyst promoted the yield of monomeric aromatic hydrocarbons. Elfadly et al. [10] reported production of aromatic hydrocarbons from catalytic pyrolysis of lignin over acid-activated bentonite clay, where it was aslo demonstrated that yield of aromatic hydrocarbons increased by acidification of the bentonite with strong acid (HCl). The HCl-activation was believed to enhance the activity of the catalyst by improving its textural properties and increasing the strong Bronsted acid sites. According to the study reported in the previous chapters, zeolites with higher total acidity and more Bronsted acid sites were also demonstrated to be favorable for the production of monomeric aromatics/phenolics from CFP of HL. Among all zeolites tested (Zeolite X, Zeolite Y and ZSM- 5), ZSM-5 with moderate total zeolite catalysts but more strong Bronsted acid sites was determined to be the best catalyst for production of monomeric aromatics/phenolics from CFP of HL at 450C. The main objective of the present study was to further enhance the activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis by increasing the strength of the acidity [8-10] or incorporation metals (metal- supported solid acids are common catalysts for hydro-de-oxygenation upgrading of bio-oils [3]).

To this end, acidification treatment (with H2SO4 and H3PO4) and metal (Ni) loading were performed on the ZSM-5 zeolite, and the catalytic performance of these catalysts was evaluated by conducting CFP of HL at 450ᵒC using ZSM-5 zeolites with various strengths of acidity (ZSM-

5 and Ni-ZSM-5 with moderate Lewis and Bronsted sites, H2SO4-ZSM-5 and H3PO4-ZSM-5 with more Bronsted sites).

5.2 Materials and methods

5.2.1 Materials

The ZSM-5 (CBV-8014) powder in ammonium form with Si/Al molar ratio of 80 was purchased from Zeolyst International (PA, USA). The hydrolysis lignin was supplied by FPInnovations, which is a by-product extracted from aspen using a proprietary hardwood fractionation process (or

123 called TMP-BioTM process) developed by FPInnovations [11]. The HL contains approximately 50- 60% lignin weight balanced by residual cellulose and carbohydrates and the molecular weight of HL is not measurable due to insolubility in any a common solvent. Nickel nitrate hexahydrate was purchased from Sigma-Aldrich. Reagent grade phosphoric acid (≥85.0%) and acetone were purchased from Caledon Laboratories Ltd (ON, Canada), ACS reagent grade sulfuric acid solution (≥98.0%) was supplied from VMR, USA, and di-n-butyl ether was provided by Alfa Aesar, USA.

5.2.2 Catalyst Preparation

5.2.2.1 Preparation of acidic ZSM-5 activated by H2SO4 and H3PO4

Acidified ZSM-5 was prepared by wet impregnation method. In a typical run, 10 g of ZSM-5 was immersed and stirred into the 100 g of 0.5 mol/L of acid solution for 0.5 h (1:10 solid to liquid ratio in weight). Then, the slurry was filtered and washed several times with distilled water for -2 -3 removing any unreacted SO4 or PO4 ion. The product was dried overnight in an oven at 105 ᵒC in air. The powder form catalyst was then calcined in a muffle furnace at 450 ᵒC for 4 h in air. To be consistent with the preparation Ni-ZSM-5 catalyst, the H2SO4-ZSM-5 or H3PO4-ZSM-5 was -1 also in-situ treated in 140 mLmin H2 flow at 550 ᵒC for 4 h before being used for CFP of HL.

5.2.2.2 Preparation of Ni-ZSM-5

Ni-ZSM-5 supported catalyst (5 wt.% Ni with respect to the weight of the support) was prepared by impregnation method. In a typical run, 0.625 g of nickel nitrate hexahydrate was dissolved in 20 mL of distilled water and 4 g of ZSM-5 (CBV-8014) was added under magnetic stirring for 4 h. The excess water was removed by oven drying at 105ᵒC in air overnight. The supported Ni catalyst was then calcined in a muffle furnace in air at 550ᵒC for 4 h. The calcined catalyst was in-

-1 situ reduced by H2 flow (140 mLmin ) at 550ᵒC for 4 h before it was used for CFP of HL.

It should be also noted that before being used for CFP of HL, all catalyst powders were pelletized then crushed and sieved to particles of a size range of 420-850 µm. The regeneration of the used catalyst was performed by calcining the acetone-washed spent catalyst in a muffle furnace at 500°C in air for 4 h.

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5.2.3 Catalyst characterization

The crystalline structure of the fresh/spent/regenerated zeolite catalysts were characterized by X- ray diffraction (XRD) on a Rigaku–MiniFlex powder diffractometer (Woodlands, USA), using

Cu-Kα (λ = 1.54059 Å) over the 2θ range of 10°-70° with a step width of 0.02°. Textural properties of the fresh/spent/regenerate catalysts were measured by N2 isothermal adsorption at 77 K (NOVA 1200e surface area and pore size analyzer). The specific surface area was calculated using

Brunauer-Emmett-Teller (BET) method. Total pore volume was estimated using the volume of N2 gas adsorbed at a relative pressure (P/P0) of 0.99. Density functional theory (DFT) was used to calculate the pore size distribution based on N2 desorption isotherm. The total acidity of the catalysts was measured by NH3-Temperature Program Desorption (NH3-TPD), carried out on a Quantachrome ChemBET Pulsar TPR/TPD automated chemisorption analyzer. In a typical experiment, about 0.1 g of the sample was pre-treated at 300°C for 1 h under a flow of helium (99.9%, 120 cm3min-1). After pretreatment, the sample was saturated with anhydrous ammonia at 100 °C for 10 min and subsequently flushed with He at the same temperature to remove any physisorbed ammonia. Then, TPD analysis was carried out by heating the sample in helium from ambient temperature to 600°C at 10 °Cmin-1 and the desorbed ammonia was measured by a thermal conductivity detector. The carbon/coke deposition for spent catalysts was characterized by thermogravimetric analysis (TGA) on a PerkinElmer Pyris 1 TGA by heating the spent catalyst in 20 cm3min-1flow of air from 40C to 800C at 10 Cmin-1. The strength of the Bronsted and Lewis acid sites of the zeolites was measured by pyridine FT-IR. A small amount of zeolite (0.2 g) was oven dried at 105˚C for 2hrs. Then 50 µL of pyridine was added to the catalyst followed by oven- drying at 105˚C for another 2 hrs. Thereafter, 2 mg of catalyst was mixed with 200 mg of KBr and pressed to make a disc that was subsequently analyzed by FT-IR to examine the Bronsted and Lewis acid sites on the catalyst.

5.2.4 Catalytic fast pyrolysis and vapor upgrading process

CFP experiments were carried out in a drop-tube/fixed bed reactor made of SS 316L tube (3/4 inch O.D., 26.5-inch length). The schematic diagram of the reactor is shown in Fig. 5-1. The reactor was heated in an electric furnace whose temperature was controlled by a calibrated temperature

125 controller. The furnace temperature could be varied from 200 to 1200ᵒC. The flow rate of nitrogen gas, flowing downward through the biomass feeder and the reactor, was set and controlled with a mass flow calibrated controller meter (Bronkhorst High-Tech EL-FLOW).

3 - The CFP experiments were carried out at 450ᵒC with sweeping N2 gas at a flow rate of 97 cm min 1. In a typical run, 2 g of HL feedstock was loaded into the feeder (1-inch OD tube) above the reactor separated from the reactor by a ball valve, and 0.4 g of quartz wool was put in the bottom of the reactor as a support for the catalyst-bed of 2 g of catalyst in the tubular reactor positioned in the hot-zone of the furnace, as illustrated in Fig. 5-1. 0.4 g of quartz wool was loaded on the top of the catalyst-bed to separate the HL and pyrolysis char from the catalyst bed. Before starting the experiment, the reactor and the feeder were vacuumed/purged thrice repeatedly to eliminate air inside the reactor system, and leak-proof was ensured by pressurizing the reactor system with high- pressure nitrogen gas before each experiment. The reactor was then heated up to 450ᵒC at 10-20 3 -1 °C/min in 97 cm min flow of N2. After the reactor temperature reached the specified temperature, the HL particles in the feeder were fed into the reactor rapidly by opening the ball valve. Assuming 3 -1 negligible change in total gas flow rate (97 cm min N2) during the pyrolysis experiments, the residence time of the vapor inside the 2 g catalyst bed (about 0.8 cm3 volume) was estimated to be < 0.5 s, and the heating rate of the feedstock in the CFP experiment was estimated at > 750 C/s. The vapor product from the reactor was condensed into a liquid product in a condensation trap refrigerated at −6°C. The non-condensable gaseous products were collected for 20 min after feeding the feedstock using a gas-bag for GC-TCD analysis.

126

Figure 5-1 Schematic diagram of the catalytic fast pyrolysis reactor.

5.2.5 Product separation

After the reactor was cooled down to room temperature, the reactor was opened and the whole reactor system was rinsed with 150 ml of reagent grade acetone to completely recovery of all liquid product (i.e., pyrolysis oil) on the inner reactor wall, on the solid residue (char), packed glass wool and catalyst bed, as well as in the condensation trap. The rinsing acetone was removed by evaporation under reduced pressure in a rotary evaporator at 45ᵒC, and the product was weighed and designated as pyrolysis oil or simply bio-oil. Then, the char residue and spent catalyst were collected and oven dried at 105ᵒC for an hour to a constant weight to determine char yield and to

127 recover the spent catalyst. The overall yield (wt.%) of pyrolysis products were calculated based on the equation (5-1):

푚푎푠푠 표푓 푙𝑖푞푢𝑖푑, 푠표푙𝑖푑, 표푟 푔푎푠 (푔) Yield (bio-oil, char, or gas) (wt.%) = × 100 (5-1) 퐷푟푦 푚푎푠푠 표푓 푓푒푒푑 (푔)

5.2.6 Products analysis

The gas samples were analyzed by GC-TCD (Agilent 3000 Micro-GC) equipped with dual columns (Molecular sieve and PLOT-Q) and thermal conductivity detectors. Elemental analysis of the HL feedstock, bio-oils and chars were analyzed with an elemental analyzer (CHNS-O Analyzer FLASH EA 1112 SERIES, Thermo Scientific), and their higher heating values (HHVs) were calculated based on the Dulong’s formula [12]. The water content of bio-oil was determined by Karl-Fisher titration method using a Mettler Toledo DL32 colorimetric titrator. The viscosity and pH values of bio-oil were measured with a viscosity meter (CAP 2000+ Viscometer, Brookfield) and pH meter (ORION 2STAR PHBenchtop, Thermo Scientific), respectively.

The bio-oil samples were quantitatively analyzed with a gas chromatograph-mass spectrometer [GC-MS, Agilent Technologies, 5977A MSD) with an SHRXI -5MS column (30 m × 250 mm × 0.25 mm) and a temperature program of 60ᵒC (hold for 2 min) → 120ᵒC (10 ᵒC/min) → 280ᵒC (8 ᵒC /min, hold for 5 min)] (bio-oils samples before and after evaporation were compared and no significant difference in the measurement). Compounds in the oil were identified by means of the NIST Library with 2011 Update and the concentrations of the low boiling point volatile compounds (including the target monomeric aromatics) in the bio-oil samples were determined using di-n-butyl ether as an internal standard. Molecular weight distributions of the bio-oils were measured by Waters Breeze GPC-HPLC instrument equipped UV detector using styragel HR 1 as the analytical column at 40°C using 1 cm3min-1 THF as the mobile phase. Polystyrene narrow standards were used for calibration of the GPC-UV.

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5.3 Results and discussion

5.3.1 Fresh catalysts characterization

Table 5-1 shows textural properties of the fresh catalysts used in this work. The ZSM-5 catalyst has microporous structure with an average pore size of 1.3 nm, BET specific surface area of 380 2 3 m /g and a total pore volume of 0.25 cm /g. The two acidified ZSM-5 catalysts (H2SO4-ZSM-5 or

H3PO4-ZSM-5) both have similar textural properties as the untreated ZSM-5 catalyst. However, Ni-ZSM-5 with 5 wt.% nickel loaded has reduced BET surface area (305 m2/g) , which is actually expected due to the deposition of metal ions inside the micropores, evidenced by the slightly increased average pore size (1.6 nm) compared with that of the ZSM-5 (1.3 nm).

Table 5-1 Textural properties of the fresh catalysts.

Catalyst name BET Specific Total pore Average pore Surface Area (m2/g) volume (cm3/g) size (nm)

H₂SO₄-ZSM-5 381 0.26 1.4

H₃PO₄-ZSM-5 401 0.28 1.4

ZSM-5 380 0.25 1.3

Ni-ZSM-5 305 0.24 1.6

The pyridine FT-IR spectra of all fresh catalysts used (H₂SO₄-ZSM-5, H₃PO₄-ZSM-5, ZSM-5, Ni- ZSM-5 and ZSM-5) are presented in Fig. 5-2. As indicated in the Figure, the IR adsorption band at around 1545 cm-1 can be ascribed to the Bronsted acid sites in the catalyst, the band at around 1450 cm-1 for Lewis acid sites, and the band at around 1490 cm-1 for both Lewis and Bronsted acid sites [20]. From Fig. 5-2, it is apparent that all ZSM-5 based catalysts contain both Lewis and Bronsted acid sites. ZSM-5 and Ni-ZSM-5 have weak Lewis acid sites and Bronsted acid sites. As expected, both acid sites, in particular Bronsted acid sites, in two acidified ZSM-5 catalysts (H₂SO₄-ZSM-5, H₃PO₄-ZSM-5) are remarkably higher than those of the untreated ZSM-5 catalyst,

129 which might contribute to some interesting performance of these two acidified zeolite catalysts in CFP of HL.

H₂SO₄-ZSM-5

H₃PO₄-ZSM-5

ZSM-5 Transmittance (%) Transmittance Ni-ZSM-5

Lewis Lewis & Bronsted Bronsted Lewis

1400 1450 1500 1550 1600 1650 Wave number (cm⁻¹)

Figure 5-2 Pyridine FT-IR spectra of fresh catalysts of H₂SO₄-ZSM-5, H₃PO₄-ZSM-5, ZSM-5, Ni-ZSM-5 and ZSM-5.

5.3.2 Effect of catalyst on products yields

Pyrolysis products yields over 4 different catalysts, compared with blank test without catalyst, are shown in Fig. 5-3. Irrespective of the use of catalyst, the bio-oil and char yields in all tests remained almost the same in the narrow ranges of 53-58% and 27-30%, respectively, whereas the presence of a catalyst consistently produced a higher gas yield, 13-17%, compared with 11% gas yield without catalyst. The maximum gas yield (17%) was observed with the H2SO4-ZSM-5 which has

130 the most strong Bronsted acid sites, suggesting the presence of the acid sites catalyze the cracking, decarbonylation, decarboxylation, hydrocracking, and hydro-deoxygenation reactions of the pyrolysis vapor, leading to increased gas formation [3, 7], which was also observed in our studies reported in the previous chapters.

100

Yield (wt.%) Yield 40

Bio-oil Gas Char

Figure 5-3 Catalytic fast pyrolysis products yield over different catalysts at 450 ˚C.

5.3.3 Gas analysis

Table 5-2 shows the gas compositions (presented in volume %) from CFP of HL, analyzed by GC-TCD. The data presented are on a nitrogen-free basis. Using a catalyst commonly increased the compositions of all gases species, apparently due to enhanced reactions such as cracking, decarbonylation, decarboxylation, hydrocracking, and hydro-deoxygenation in the presence of

131 acid catalysts [3,7], which is in a good agreement with the higher gas yield in all catalytic experiments (Fig. 5-3). For all runs with or without catalyst, the C1 – C3 gas compositions are similar, i.e., 5-7% CH4, 13-17% CO, 35-51% CO2 and 16-37% C3 gases. Interestingly, the hydrogen composition in the presence of Ni-ZSM-5 being 16.08±5.0% is much higher than that in other runs (1-6%), which might be attributed to steam reforming reaction of hydrocarbons (CH4 +

2H2O → 4H2 + CO2) or the gas-water shift reaction (CO + H2O → H2 + CO2). Both reactions could be catalyzed by nickel-based catalysts. Herewith the water was mainly pyrolytic water from the HL pyrolysis, but deoxygenation of pyrolysis vapor over the Ni-catalyst bed could also form water and contribute to the formation of hydrogen [14,15].

Table 5-2 Gas composition (vol%) from the catalytic fast pyrolysis of hydrolysis lignin.

Catalyst Name H₂ CH₄ CO CO₂ C₃

None 2.3±0.0 18.6±0.1 76.0±0.7 1.2±0.0

H₂SO₄-ZSM-5 1.5±0.3 5.1±1.8 17.0±5.8 45.9±9.4 30.5±1.5

H₃PO₄-ZSM-5 2.0±0.6 5.2±2.0 16.8±6.5 50.4±11.3 25.6±2.2

ZSM-5 2.7±0.2 4.8±0.4 12.1±1.1 45.1±1.3 33.2±2.7

Ni-ZSM-5 16.1±5.0 4.9±1.7 13.0±4.7 50.6±11.7 15.5±0.3

5.3.4 Bio-oil analysis

5.3.4.1 Physical properties and elemental compositions

Table 5-3 gives the physical and chemical properties the pyrolysis oil collected in the tests with and without catalyst at 450 ᵒC. The ZSM-5, acidified and Ni-loaded ZSM-5 catalysts all produced bio-oils with better quality than the oil produced without catalyst with respect to higher pH values, reduced viscosity, increased HHV and lower O/C ratio. Specifically, the presence of catalyst in CFP of HL led to increasing the oil’s pH from 4.32 without catalyst to 5.22-5.72 owing to the

132 catalyzed decarboxylation reactions, reducing oil viscosity from 7.10 cP to 4.56-5.28 cP, improving the oil’s HHV from 17.44 MJ/kg to 19.08-27.83 MJ/kg, increasing the oil’s C content from 47.1% to 52.74-67.42%, decreasing O content from 45.76% to 25.18-40.74%, reducing O/C and H/C from 0.7 to 0.3-0.6, and 1.7 to 1.2-1.4, respectively. Among all catalysts, the two acidified catalysts, in particular the H₂SO₄-ZSM-5, produced bio-oils with best quality, e.g., the highest pH value (5.72), the highest HHV (27.83 MJ/kg), the highest C content (67.42%) and the lowest O content (25.18%) and the smallest O/C (0.3). H₂SO₄-ZSM-5 has the strongest Bronsted acid sites that could significantly catalyze the cracking/hydrodeoxygenation/dehydration reactions [16,17] and hence lead to the best quality of the oil products. The promoted hydrodeoxygenation/dehydration reactions in all catalytic runs might be evidenced by the increased formation of CO2 in the gaseous products (Table 5-2) and the higher H2O content in the bio-oils (8.11 wt.% without catalyst to 7.17-18.27 wt.% with catalyst, as displayed in Table 5-3). Besides, the effects of catalyst on molecular weights of the bio-oils are less significant, and they are in relatively narrow ranges: Mn = 140-193 g/mol and Mw = 214-379 g/mol with a polydispersity index (PDI) of 1.5-1.9.

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Table 5-3 Physical and chemical properties of the bio-oils.

Catalyst Mn Mw PDI pH Viscosity Water Elemental composition HHV O/C H/C (g/mol)5 (cP)1 content (d.b.%) (MJ/kg)3 (-) (-) (g/mol)5 (wt.%) C H N O2

None 153 230 1.5 4.32 7.10 8.11 47.10 6.78 0.36 45.76 17.44 0.7 1.7

H₂SO₄-ZSM-5 179 295 1.6 5.72 5.19 18.27 67.42 6.68 0.73 25.18 27.83 0.3 1.2

H₃PO₄-ZSM-5 172 277 1.6 5.44 5.28 15.63 65.41 6.82 0.26 27.51 26.94 0.3 1.3

Ni-ZSM-5 193 379 1.9 5.22 4.56 7.17 52.74 5.96 0.32 40.74 19.08 0.6 1.4

ZSM-5 140 214 1.5 5.60 9.60 32.30 62.60 5.70 0.50 31.20 23.70 0.4 1.1

1 Measured at 50 ᵒC; 2 By difference and assuming negligible sulfur and ash contents; 3 Calculated by Dulong formula HHV (MJ/ kg) =0.3383C + 1.422 (H -

4 O/8); Mn and Mw are the number-average and weight-average molecular weights determined by GPC-UV.

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5.3.4.2 Compositions and yields of monomeric aromatics/phenolics

The produced bio-oils from CFP of HL at 450ᵒC with and without catalyst are quantitively analyzed for their low-boiling point compositions (including our target monomeric aromatics/phenolics) by GC-MS with di-n-butyl ether as an internal standard. As an example, the typical ion chromatogram for the boil-oil obtained with H2SO4-ZSM-5 catalyst (the best catalyst with respect to oil quality) is presented in Fig. 5-4. The main objective of the current work was to examine the effects of acid strength of the ZSM-5 catalyst (Bronsted and Lewis sites) on the catalyst’s activity for the production of monomeric aromatics and phenolics. The aromatic/phenolic compounds detected by GC-MS were divided into four distinct groups: (1) BTX including compounds such as benzene, toluene, xylene, ethyl toluene and trimethylbenzene; (2) monomeric phenolics such as phenol, guaiacol, cresol, eugenol,iso-eugenol,4-ethylguaiacol, 2- methylphenol, 2,5-dimethylphenol; (3) naphthalenes including naphthalene, 2-methylnaphthalene, 1,7-, 1,3-, and 2,6- dimethyl naphthalene, 1,2,4-, 1,4,5-, and 1,6,7-trimethyl naphthalene, etc.; (4) other monomeric aromatic/phenolic compounds, e.g., 2-methoxy-4-vinyl phenol, syringol, 4- methoxy-3-methoxymethyl phenol, 3-methoxy-1,2-benzenediol, etc.

3 3

2.5 Internal Standard 2 4

Millions 3 2 3 4 3 1 2 1.5 2 2 1 2 1 2 1 1

Abundance 0.5 1 0 2.5 4.5 6.5 8.5 10.5 12.5 14.5 Time (min)

135

Compositions of GC-MS detectable aromatics/phenolics in bio-oils obtained with various catalysts are shown in Fig. 5-5. The results reveal that in all bio-oils from pyrolysis of HL with/without catalyst the 10 – 40% of the mass of the oils was detectable by GC-MS as low boiling-point aromatics/phenolics, due to the limitation of GC-MS useful for volatile compounds only [18]. From this Figure, the presence of a catalyst significantly promoted the yields of aromatics/phenolics, and again the H2SO4- ZSM-5 catalyst (with the strongest Bronsted acid sites) produced the maximum amount of all four groups of aromatics/phenolics in resulted bio-oil, demonstrating that the strong Bronsted acid sites in the catalyst could catalyze cracking/hydrodeoxygenation/dehydration reactions of the pyrolysis vapor [10][16,17], leading to the production of more aromatic/phenolic compounds in CFP of HL. Fig. 5-6 presents total yield of monomeric aromatics/phenolics (mg/g-HL) obtained from CFP of HL over various catalysts at temperature 450ᵒC, from which it is obvious that the H2SO4- ZSM-5 catalyst (with the strongest Bronsted acid sites) produced the maximum total yield of monomeric aromatics/phenolics, being 151 mg/g-HL, compared to 68 mg/g-HL without catalyst, 84 mg/g-HL with ZSM-5, 96 mg/g-HL with H3PO4- ZSM-5 catalyst, and 85 mg/g-HL with Ni-ZSM-5.

136

160.00 BTX 140.00 Monomer Phenolics

Naphthalene Group oil) - 120.00 Other Monomer Aromatics

100.00

80.00

60.00

40.00 Compositions (mg/g (mg/g bio ofCompositions 20.00

- No Catalyst ZSM-5 Ni-ZSM-5 H₂SO₄-ZSM-5 H₃PO₄-ZSM-5

Figure 5-5 Compositions of GC-MS detectable aromatics/phenolics in bio-oils obtained with various catalysts.

137

160

140

120

100

80 HL)

20 Total yield of monomeric aromatics/phenolics (mg/g (mg/g of monomeric of aromatics/phenolics yield Total -

Figure 5-6 Total yield of monomeric aromatics/phenolics (mg/g-HL) obtained from CFP of HL over various catalysts at temperature 450 ᵒC.

5.3.5 Spent catalyst characterization

5.3.5.1 Catalyst crystalline structure

XRD patterns of the fresh and spent catalysts of H2SO4-ZSM-5, H3PO4-ZSM-5 and Ni-ZSM-5 are displayed in Fig. 5-7. In the XRD patterns of all catalysts (fresh/spent), the multiple strong peaks are typical XRD lines of zeolite. After the pyrolysis experiments at 450 ᵒC, no significant change can be observed in the zeolite XRD peaks in all spent catalysts, except Ni-ZSM-5 whose XRD lines are markedly weakened, probably due to the masking effects of the carbon/coke deposition on the supported metal catalyst [19]. The above results confirm that the ZSM-5 zeolite-based

138 catalysts have good thermal stability, while in fact from the literature, collapsing of zeolite crystalline structure normally starts at a temperature higher than 760ᵒC [20].

• ZSM-5 ○ NiO Spent Ni-ZSM-5

○ Fresh Ni-ZSM-5

Spent H3PO4-ZSM-5

XRD Intensity (a.u.) Intensity XRD Fresh H3PO4-ZSM-5

• Spent H2SO4-ZSM-5

• •

• •• • • •• •• • Fresh H2SO4-ZSM-5

0 10 20 30 40 50 60 2Ѳ

Figure 5-7 X-ray diffraction patterns for the fresh and the spent catalysts of selected catalysts from pyrolysis of HL at 450 ᵒC for 20 min [21].

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5.3.5.2 Catalyst acidity analysis

The NH3-TPD profiles for the fresh, spent and regenerated catalyst of H2SO4-ZSM-5 and H3PO4- ZSM-5 are shown in Fig. 5-8, and the total acidity of these catalysts are listed in Table 5-4. As illustrated in the Fig. 5-8, in all NH3-TPD profiles, two distinct NH3-desorption peaks at about 240ᵒC and ᵒC, which are frequently marked as weak and strong acid sites, respectively. The Figure also clearly shows that the NH3-desorption peaks (for both strong acid and weak acid sites) weaken in the NH3-TPD profiles of the spent catalysts when compared to those of the fresh catalysts, suggesting the loss of both strong acid (Bronsted acid) and weak acid (Lewis acid) sites in these spent catalysts after the pyrolysis experiments [15,21]. From Table 5, the total acidity of the H₂SO₄-ZSM-5 (0.97 mmol/g) is much higher than that of H₃PO₄-ZSM-5 (0.51 mmol/g), which is in a good agreement with the Pyridine FT-IR analysis results (Fig. 5-2) indicating that the H₂SO₄- ZSM-5 has much higher Bronsted and Lewis acid sites that H₃PO₄-ZSM-5. As clearly shown in this Table, the total acidity of both fresh catalysts decreased after CFP of HL experiments, and the spent catalysts after regeneration regained their acidity, suggesting good regenerability of these two acidified ZSM-5 catalysts.

3.5 H₂SO₄-ZSM-5 3 R-H₂SO₄-ZSM-5 2.5 S-H₂SO₄-ZSM-5 2 1.5

1 TCD Signal (mV) Signal TCD 0.5 0 100 200 300 400 500 600 Temperature (ᵒC)

140

3 H₃PO₄-ZSM-5 2.5 S-H₃PO₄-ZSM-5 R-H₃PO₄-ZSM-5 2

1.5

1 TCD Signal (mV) Signal TCD 0.5

0 100 200 300 400 500 600

Temperature (ᵒC)

Figure 5-8 NH3-TPD profiles of the fresh, spent and regenerated catalysts of H₂SO₄-ZSM-5 and H₃PO₄-ZSM-5.

Table 5-4 Total acidity of the fresh, spent and regenerated catalysts of H₂SO₄-ZSM-5 and H₃PO₄-ZSM-5.

Total acidity (mmol/g) Catalyst Fresh Spent Regenerated

H₂SO₄-ZSM-5 0.97 0.28 0.38

H₃PO₄-ZSM-5 0.51 0.35 0.46

5.3.5.3 Carbon/coke deposition on the spent catalysts

In order to examine the amount of carbon/coke deposition on the spent catalysts, thermogravimetric analysis (TGA) was conducted on the spent catalysts heated at 10 ᵒC/min from 40ᵒC up to 800ᵒC in 20 ml/min air. The TG and DTG profiles of the spent catalysts of H₂SO₄- ZSM-5, H₃PO₄- ZSM-5 and Ni-ZSM-5 are illustrated in Fig. 5-9.

141

100 (a) 90

Weight (%) Weight H₂SO₄-ZSM-5 50 H₃PO₄-ZSM-5 40 Ni-ZSM-5 30 0 100 200 300 400 500 600 700 800 Temperature (ᵒC)

0.1 (b) 0 -0.1 -0.2 -0.3

-0.4 H₂SO₄-ZSM-5 H₃PO₄-ZSM-5 -0.5 Deriv. weight (%/min) Deriv. Ni-ZSM-5 -0.6 0 100 200 300 400 500 600 700 800 Temperature (ᵒC)

Figure 5-9 TG (a) and DTG (b) profiles of the spent catalysts of H₂SO₄-ZSM-5, H₃PO₄- ZSM-5 and Ni-ZSM-5.

As shown in the TG profiles, the mass loss up to 100 ᵒC (~2% for all three samples) can be ascribed to physically absorbed moisture in the spent catalysts samples. The weight loss between 100 and 600ᵒC (~ 8-10%), which peaked at ~530 ᵒC (from the DTG curves), might be attributed to the decomposition of the condensed heavy volatile compounds (acetone insoluble tar) deposited on these catalysts during CFP of HL. The weight loss (1-2%) at 600 – 800ᵒC could be attributed to

142 the carbon/coke deposition on the catalyst’s surface during the pyrolysis. Therefore, the carbon/coke deposition on all spent catalysts was negligibly low, suggesting that the catalysts of H₂SO₄-ZSM-5, H₃PO₄- ZSM-5 and Ni-ZSM-5 have superb resistance to carbon/coke deposition in CFP of HL. The excellent resistance to carbon/coke deposition for these three modified ZSM-5 catalysts can also be evidenced by the negligible deterioration in the textural properties of these catalysts after the CFP experiments and after regeneration, as shown in Table 5-5. The superb resistance to carbon/coke deposition for these three modified ZSM-5 catalysts might be attributed to their microporous structure (1-2 nm average pore size), smaller pore volume (0.2-0.3 cm3/g) and relatively high BET specific surface area (305-401 m2/g)(Table 5-5), but high acidity (Fig. 6- 2, Table 6-4). Generally, a catalyst with higher acidity and larger pore volume are more susceptible to carbon/coke deposition [21–23].

Table 5-5 Textural properties of the acidified and metal loaded ZSM-5 catalysts.

BET surface Total pore Average pore Catalyst area (m²/g) volume (cc/g) size (nm)

H₂SO₄-ZSM-5 (Fresh) 381 0.26 1.4

H₂SO₄- ZSM-5 (Spent) 302 0.20 1.5

H₂SO₄- ZSM-5 (Regenerated) 320 0.22 1.3

H₃PO₄- ZSM-5 (Fresh) 401 0.28 1.4

H₃PO₄- ZSM-5 (Spent) 291 0.21 1.4

H₃PO₄- ZSM-5 (Regenerated) 317 0.21 1.3

Ni- ZSM-5 (Fresh) 305 0.24 1.6

Ni- ZSM-5 (Spent) 188 0.14 1.5

Ni- ZSM-5 (Regenerated) 294 0.20 1.4

143

5.4 Conclusions

This work aimed to further enhance the activity of ZSM-5 zeolite catalyst for the production of monomeric aromatics/phenolics from hydrolysis lignin via catalytic fast pyrolysis. Some key conclusions from this work are summarized as follows: (1) All ZSM-5 based catalysts contain both Lewis and Bronsted acid sites. ZSM-5 and Ni- ZSM-5 have weak Lewis acid sites and Bronsted acid sites, and both acid sites, in particular Bronsted acid sites of two acidified ZSM-5 catalysts (H₂SO₄-ZSM-5, H₃PO₄-ZSM-5) are remarkably higher than those of the untreated ZSM-5 catalyst. (2) Irrespective of the use of catalyst, the bio-oil and char yields in all tests remained almost the same in the narrow ranges of 53-58% and 27-30%, respectively, whereas the presence of a catalyst consistently produced a higher gas yield. (3) Among all catalysts, the two acidified catalysts, in particular the H₂SO₄-ZSM-5, produced bio-oils with best quality, e.g., the highest pH value (5.72), the highest HHV (27.83 MJ/kg), the highest C content (67.42%) and the lowest O content (25.18%) and the smallest O/C (0.3). H₂SO₄-ZSM-5 has the strongest Bronsted acid sites that could significantly catalyze the cracking/hydrodeoxygenation/dehydration reactions and hence lead to the best quality of the oil product.

(4) The H2SO4- ZSM-5 catalyst (with the strongest Bronsted acid sites) produced the maximum total yield of monomeric aromatics/phenolics, being 151 mg/g-HL, compared

to 68 mg/g-HL without catalyst, 84 mg/g-HL with ZSM-5, 96 mg/g-HL with H3PO4- ZSM- 5 catalyst, and 85 mg/g-HL with Ni-ZSM-5.

(5) The H2SO4-ZSM-5 demonstrated to be thermally stable and has superb resistance to carbon/coke deposition, owing to its microporous structure, relative large BET surface area and presence of strong Bronsted acid sites.

5.5 Acknowledgments:

The financial support for this work was provided mainly through the NSERC Discovery Program, NSERC/FPInnovations Industrial Research Chair Program in Forest Biorefinery, and BioFuel Net.

144

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[22] Park HJ, Heo HS, Jeon JK, Kim J, Ryoo R, Jeong KE, et al. Highly valuable chemicals production from catalytic upgrading of radiata pine sawdust-derived pyrolytic vapors over mesoporous MFI zeolites. Appl Catal B Environ 2010;95:365–73. doi:10.1016/j.apcatb.2010.01.015.

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Chapter 6

6 Catalytic co-liquefaction of lignin and lignite coal for aromatic liquid fuels and chemicals in mixed solvent of ethanol-water in the presence of a hematite ore

148

Abstract:

In this work, a raw hematite ore (Fe2O3) displayed to be a low-cost but effective catalyst for co- liquefaction of hydrolysis lignin (HL) and Xilinguole lignite (XL) in ethanol-water (50:50, v/v) mixed solvent under initial N2 atmosphere to produce heavy oil (HO) as a potential source of liquid fuel and aromatic chemicals. The liquefaction of HL and XL separately without catalyst resulted in a maximum of approx. 18 and 11 wt.% yield of HO, respectively, while the co-liquefaction process resulted in up to approx. 26 wt.% of HO, indicating synergy effect in co-liquefaction of lignin and lignite. The addition of the hematite ore in the co-liquefaction operation produced HO at a very high yield of about 40 wt.% at 400C for a residence time of 2 h, nearly doubling that of the operation without catalyst. The Produced HO products from the co-liquefaction operations at 400C for 2 h contain significant concentrations of low molecular weight aromatics at ~14 mg/g- HO in the presence of non-reduced hematite or goethite, and ~17 mg/g-HO in the presence of reduced hematite or goethite, compared with only <5 mg/g-HO without iron ore catalyst.

149

6.1 Introduction

Currently over 90% of the liquid fuels and chemicals are derived from fossil fuels, in particular petroleum. Due to the energy security concern and the environmental issues caused by the use of fossil fuels, there is a growing interest in producing bio-fuels (solid, liquid and gaseous) and bio- based chemicals/materials from biomass, as it is abundant, inexpensive and renewable or carbon- neutral [1–6]. Woody biomass is a particularly promising source for fuels and chemicals as it contains negligible sulfur, nitrogen and ash. Woody biomass (on a dry basis) is composed of three main components 30-40 wt.% cellulose, 20-30 wt.% hemicellulose and 20-30 wt.% lignin with the remaining 5-10 wt.% ash and extractives, depending on type of biomass [7–9]. Lignin is a natural aromatic macromolecule with cross-linked structure and molecular masses over 10,000 Da or g/mol, consisting of the following three monolignol monomers: p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) phenylpropanoid units, linked mainly via -O-4, α-O-4 or 5-5 linkages. Thus, liquefaction and de-polymerization of lignin or woody biomass produce aromatic/phenolic fuels/chemicals [6]. On the other hand, low rank coal such as lignite has abundant fused aromatic ring structure [10,11]. Thus, lignin and lignite can be natural sources of aromatic fuels and chemicals through various thermochemical conversions such as pyrolysis, liquefaction and depolymerization [6, 9].

Similar to biomass liquefaction, liquefaction of coal to produce liquid transportation fuels has become an attractive approach for some countries such as South Africa, US and China, where there are abundant coal reserves. Indirect coal liquefaction (ICL) and direct coal liquefaction (DCL) have been two well-known methods used for conversion of coal into liquid fuels, while the ICL process includes gasification followed by syngas catalytic conversion into fuels e.g. methanol, ethanol and gasoline. However, in the DCL process, coal is liquefied by a single step treatment into liquid fuels under temperature and pressure ranging between 300 – 500ᵒC and 10 – 30 MPa of hydrogen gas in the presence of appropriate solvents and catalysts. [12–14].

Co-liquefaction of coal with biomass (agricultural/forestry residues) has gained special research interest due to the potential synergy effects between biomass and coal during liquefaction [15–17], resulting in improved yields and quality (e.g., heating value, H/C ratio) of the liquid products under milder conditions of temperature and pressure, as detailed below. Co-liquefaction of cellulose and

150 low-rank coal in a supercritical water at 673 K and 25 MPa was investigated by Matsumura et al. [18], and they showed that the hydrogen released from biomass could promote coal liquefaction and had positive effect on quality of the liquefaction products. Wang et al. [19] worked on hydrothermal liquefaction of lignite, wheat straw and plastic waste in sub-critical water in a batch reactor and the effects of blending ratio of feedstocks, temperature, initial nitrogen pressure and additives on products distribution was investigated. They reported that when the mass blending ratio of lignite, wheat straw and plastic waste was 5:4:1, there existed a synergy effect for oil yield. Rafiqul et al. [20] examined hydro-liquefaction of a Chinese bituminous coal and bagasse at 350– 450°C for 15–45 min under hydrogen of a cold pressure of 300–700 psig. The addition of bagasse to the coal in liquefaction increased the oil yield, reaching 48% at the optimum conditions (420 °C, 500 psig of cold hydrogen pressure and 40 min of reaction time). In a study by Ikenaga et al. [21] in co-liquefaction of microalgae with Yallourn coal (1:1 wt/wt) under H2 at 5 MPa (cold pressure) in 1-methyl-naphthalene achieved 99.8% coal conversion and produced 65.5% yield of hexane- soluble oil at 400°C with Fe(CO)5 catalyst. In a another work by Li et al. [17], co-liquefaction of corn stalk and Shengli lignite were investigated, where the synergy effect was observed, which could be attributed to free radicals or intermediates produced by thermally degradation of corn stalk and lignite. Significant increases in solids conversion by 8.67% and in oil yield by 6.46% were obtained when co-liquefaction of corn straw/lignite at 4/6 mass blending ratio.

However, the use of tetralin, an expensive solvent with a high-boiling point, as the liquefaction solvent brings about some practical problems, e.g., high cost of the solvent, and poor recyclability of the solvent from the liquefied products. As a result, other low boiling point organic solvents, such as alcohols and cyclic carbonates were tested as solvents for low-temperature liquefaction of biomass [22]. These solvents could be easily recycled by evaporation after liquefaction and are much cheaper than tetralin. In a study by the authors’ group, 50 wt.% methanol-water or ethanol- water mixed solvent was found to be highly effective for the liquefaction of white pine sawdust

[23]. The 50 wt.% aqueous alcohol at 300°C for 15 min under N2 produced a 65% yield of bio- oil and >95% biomass conversion. In another study by the authors’ group [24], raw iron ore was found to be a very effective catalyst for direct liquefaction of peat into bio-crude in supercritical water in N2 atmosphere, at 400°C for 2 h. The addition of the raw iron ore produced a very high yield of heavy oil (HO), being ~40% nearly double that of the operation without catalyst.

151

This work aimed to investigate co-liquefaction of a lignite coal with a lignin in a low boiling point solvent (i.e., ethanol-water mixed solvent) using an inexpensive iron ore catalyst in N2 atmosphere (without using high-pressure hydrogen). The synergy effects in the co-liquefaction and effects of the catalyst on characteristics of the HO products obtained from the co-liquefaction were examined.

6.2 Experimental

6.2.1 Materials

The hydrolysis lignin (HL) used in this study was provided by FPInnovations and was not soluble in common solvent [25]. HL was the residual of sugar/ethanol production by TMP-Bio process from Aspen wood. The HL consists of 56.7 wt.% of lignin and 29.8 wt.% of carbohydrates. A Chinese Xilinguole lignite (XL) coal was used in this study. The coal and lignin were vacuum dried at 80⁰C overnight prior to use. The proximate and ultimate analysis results of the HL and XL feedstocks are given in Table 6-1. All solvents used are commercial pure chemical reagent (purity higher than 99.5%) without further purification supplied from Sinopharm Chemical Reagent.

Table 6-1 Proximate and ultimate analysis of the HL and XL.

Proximate analysis, wt.% (db)a Ultimate analysis, wt.% (daf)b HHV

d Fixed c (MJ/.kg) Volatile matters Ash C H N S O carbon

HL 71.42 1.89 26.69 49.76 6.45 0.33 - 43.46 18.27

XL 32.95 8.73 58.32 63.89 4.35 0.94 0.61 30.21 22.41 a Dry base; b Dry and ash free; c By difference; Calculated by Dulong formula [HHV (MJ/kg) =

0.338 × C + 1.428 × (H – O/8)].

152

6.2.2 Iron ore catalysts

The primary catalyst tested in this work was a hematite ore obtained from a local mine in Ma’anshan, Anhui, China. The raw hematite ore was analyzed by X-ray fluorescence (XRF), and the XRF measurement results are shown in Table 6-2. The raw hematite is mainly composed of

91.72±0.1 wt.% Fe2O3 and 3.66±0.1 wt.% SiO2 and 3.06±0.1 wt.% Al2O3. For reference, a synthetic goethite (FeOOH) was prepared and used in comparison with the hematite ore, as well as the in-situ reduced hematite and goethite obtained by hydrogen reduction at 400C for 4 h. The synthetic goethite was in-house prepared in the authors’ lab in the following procedures: precipitation of 45 g of FeCl3 (solid) with 300 ml of KOH (1 M) solution (both were commercial pure chemical reagent supplied from Sinopharm Chemical Reagent) at room temperature under magnetic stirring, followed by thoroughly washing using distilled water to remove the KCl byproduct and any unreacted KOH and FeCl3. The filtered paste-like powder was then dried in an oven in air at 105C overnight, and was recovered as the synthetic goethite (FeOOH). All the iron- based solid catalysts (i.e., the raw hematite, the reduced hematite, the synthetic goethite, and the reduced goethite) were crushed into fine particles of less than 100-mesh (<150 µm) before being used as the catalysts in the liquefaction experiments.

Table 6-2 XRF analysis of the raw hematite ore.

Compound wt. % Element wt. %

Fe2O3 91.72±0.1 Fe 64.15±0.1

SiO2 3.66±0.1 Si 1.71±0.0

Al2O3 3.06±0.1 Al 1.62±0.1

MnO 0.42±0.0 Mn 0.33±0.0

K2O 0.31±0.0 K 0.26±0.0

P2O5 0.22±0.0 Px 0.09±0.0

MgO 0.21±0.0 Mg 0.13±0.0

153

CaO 0.15±0.0 Ca 0.11±0.0

TiO2 0.13±0.0 Ti 0.08±0.0

Others 0.14±0.0 Others 0.10±0.0

6.2.3 Experimental setup

Hydrothermal liquefaction experiments were performed in a 50 mL stirred reactor. In a typical run, 3.0 g of mixed feedstocks of HL and XL (1:1 w/w) for co-liquefaction, or 3.0 g of HL or 3.0 g of XL for liquefaction of single feedstock, was loaded into the reactor with 30 mL water-ethanol (1:1 v/v) mixed solvent (equivalent to approx. 10 wt.% substrate concentration of the feed) together with 0.6 g catalyst (or approx. 20 wt.% in relation to the mass of the feedstock). The reactor was then sealed and the residual air inside the reactor was removed by N2 purging- vacuuming for at least five times, followed by pressurizing the reactor to 2 MPa using nitrogen. The reactor was heated with stirring to the desired temperature (350-420C), when the reactor was agitated at 600 rpm. Due to the water-ethanol vapor pressure, the reactor pressure increased as the temperature was raised to the reaction temperature. The average pressure inside the reactor during reaction was approx. 22 MPa depending on the temperature. As soon as the reactor reached the reaction temperature, it was maintained at that temperature for a specific residence time (0.5h-2 h). Then the reaction was stopped by quenching the reactor in a water/ice bath. At least 2 – 3 replicate runs were conducted for all the experiments and the reported results are the mean values. The relative errors of HO yields in all runs were mainly within ±4%.

6.2.4 Product separation

Fig. 6-1 summarizes the procedure used for separating the liquefaction products, i.e., HO, water- ethanol soluble oil (WESO), solid residue (SR), and (water + gas). Once the reactor was cooled to room temperature, the gas inside was released into a gas-collecting vessel, then the reactor was opened, and the solid/liquid products were rinsed from the reactor with distilled water. The water suspension was filtered under vacuum through a pre-weighted Whatman no. GB/T1914-2007 filter paper to separate the solid residue from the water-ethanol soluble liquid oil. Then, the filtrate was

154 evaporated under reduced pressure to completely remove solvent at 80C, and the remaining oily product was weighed and denoted as WESO. The reactor was then further rinsed with reagent grade acetone to completely remove the ethanol-water insoluble materials including HOs and the residual chars adhering on the inner reactor wall by scraping with a spatula. The slurry and rinsing acetone were collected and filtered under vacuum through the same filter paper retaining the ethanol-water insoluble solids on it. The total solid residue was rinsed with acetone until the resulting filtrate became colorless. The total solid residue was then oven dried at 80C overnight to a constant weight to determine the yield of SR and feedstock conversion. The filtrate was evaporated under reduced pressure to completely remove acetone at 45C, and the dark color oily product was weighed and denoted as HO. Yields of various products were then calculated by the following equations:

푚푎푠푠 표푓 ℎ푒푎푣푦 표𝑖푙 (푔) Yield of HO (wt.%) = × 100 (6-1) 푚푎푠푠 표푓 푑푎푓 푐표푎푙 푎푛푑 푙𝑖푔푛𝑖푛 (푔)

푚푎푠푠 표푓 푠표푙𝑖푑 푟푒푠𝑖푑푢푒 (푔) Yield of SR (wt.%) = × 100 (6-2) 푚푎푠푠 표푓 푑푎푓 푐표푎푙 푎푛푑 푙𝑖푔푛𝑖푛 (푔)

푚푎푠푠 표푓 푤푎푡푒푟−푒푡ℎ푎푛표푙 푠표푙푢푏푙푒 표𝑖푙푠 (푔) Yield of WESO (wt.%) = × 100 (6-3) 푚푎푠푠 표푓 푑푎푓 푐표푎푙 푎푛푑 푙𝑖푔푛𝑖푛 (푔)

Yield of wet gas (water + gas, wt.%) = 100 – yield of HO – yield of SR – yield of WESO (6-4)

Conversion (%) = 100 – yield of SR (6-5)

155

Figure 6-1 Separation procedure of liquefaction products.

6.2.5 Characterization of catalysts and liquefaction products

The CHNS element compositions of the feedstocks and the liquid/sold products were determined by the Vario EL III elementary analyzer, and their higher heating values (HHVs) were calculated based on the Dulong’s formula [26]. The HO products dissolved in acetone were quantitatively analyzed with a gas chromatograph-mass spectrometer [GC-MS, Agilent Technologies, 5977A MSD) with a SHRXI -5MS column (30 m × 250 mm × 0.25 mm) and a temperature program of 60C (hold for 2 min) → 120 ᵒC (10 C/min) → 280ᵒC (8 C /min, hold for 5 min)]. Compounds in the HO were identified by means of the NIST Library with 2011 Update and the concentrations of the low boiling point volatile compounds (including the target monomeric aromatics) in the HO samples were determined using di-n-butyl ether (Alfa Aesar) as an internal standard. The molecular weights and their distributions of the HOs were analyzed on a Waters Breeze gel

156 permeation chromatograph (GPC) [1525 binary high-performance liquid chromatography (HPLC) pump; UV detector at 270 nm; Waters Styragel HR1 column at 40ᵒC] using tetrahydrofuran (THF) as the mobile phase at a flow rate of 1 mL/min, and polystyrene standards were used for calibration. The gas samples were analyzed by GC-TCD (Agilent 3000 Micro-GC) equipped with dual columns (Molecular sieve and PLOT-Q) and thermal conductivity detectors. The vol.% compositions (after excluding N2) of a typical gaseous product in the co-liquefaction/liquefaction process with/without catalyst were: CO2 (56 vol.%), CH4 (20 vol.%), CO (13 vol.%) and H2 (11 vol.%)). The mass of produced gas is calculated based on the total volume of the gas and vol% of each gaseous component (excluding N2) from the GC-TCD analysis, assuming ideal gas law.

X-ray diffraction (XRD) patterns of the catalysts were collected on a Rigaku Ultima IV diffractometer, using Cu Kα radiation (λ = 0.15418 nm) at 40 kV and 40 mA. X-ray Fluorescence (XRF) measurement for the catalysts was performed with an ARL Advant'X Intellipower 3600 operating at 60 kV and 120 mA, respectively. The functional groups of the HL, XL coal and the HL-XL blend (1:1 w/w) were analyzed by Fourier Transform Infrared Spectroscopy (FTIR, Perkin Elemer) at the wave number of 600-500 cm-1 with a resolution of 4 cm-1.

6.3 Results and discussion

6.3.1 Effects of temperature

The widely acceptable reaction schemes of direct liquefaction of biomass or coal can be summarized as: first, cleavage of the weak chemical bonds in the biomass or coal, i.e. C-O-C or C-C forms intermediates that would be further converted into HO and gas [16,17]. Thus, temperature was normally found to be the most important factor during the liquefaction process [27]. Based on this, the effect of the temperature from 350 to 435C on the co-liquefaction of lignin and lignite were tested. Fig. 6-2 shows products distribution during co-liquefaction of HL and XL at various temperatures for 0.5h residence time. The total feedstock conversion (represented by the SR yield) and the (gas+water) yield, continuously increased with the rise of reaction temperature. The total conversion reached approx. 59 wt.% at 435°C, meanwhile, the (gas+water) yield increased to 36.64 wt.%, while the HO yield decreased continuously from approx. 26 wt.% to 18 wt.% by increasing the temperature from 350°C to 435°C. Although a higher temperature promotes the decomposition of coal or biomass to form intermediates, precursors of HO, but the

157 formed HO could further crack into gas or dehydrated into water at a higher temperature, as evidenced by the results of HO yield in this work, declining with increasing temperature from 350°C to 435°C, accompanied by continuously increased (gas+water) yield.

60 HO SR WESO Gas+water 50

30 Yield (wt%) Yield 20

0 350 370 390 410 430 Temperature (C)

Figure 6-2 Products distribution during co-liquefaction of HL and XL at various temperatures for 30 min residence time.

6.3.2 Effects of retention time

Fig. 6-3 shows the products distribution during co-liquefaction of HL and XL at 350 C for a residence time ranging from 0.5h to 2 h. It is shown that with an increase in reaction time from 30 min to 1 h, HO and solid residue yield decreased but they remain nearly constant after then between 1 h and 2h, while the yields of WESO and (gas+water) increased continuously in the entire time range (from 30 min to 2 h). This observation suggests that 30 min retention time may be

158 sufficiently long for the production of HO, and a longer retention time would cause further re- condensation, re-polymerization or de-hydration or increased extent of steam gasification reactions of HO, leading to the decrease in HO yield, and increased gas/H2O yield [27–29].

40 HO SR WESO Gas+water

30 Yield (wt%) Yield 20

0 0.5 1 1.5 2 Time (h)

Figure 6-3 Products distribution during co-liquefaction of HL and XL at 350 ᵒC for a residence time ranging from 0.5h to 2 h.

6.3.3 Synergy effect in co-liquefaction of lignin and lignite

In order to determine whether there is synergy effect in co-liquefaction of lignin and lignite, it is necessary to investigate the liquefaction of HL and XL separately and compare the results with those of co-liquefaction. In this work, the liquefaction of individual feedstock of XL or HL and co-liquefaction of these two feedstocks were conducted at 350°C and with 30 min retention time, and the results are compared in Fig. 6-4. It can be seen that the feedstock conversion (100% - SR yield) is 70.0 wt.% for liquefaction of HL, much higher than that of XL. 17.9 wt.%), and HO yield is 17.8 wt.% for HL, compared with 10.7 wt.% for lignite coal, suggesting that the lignin has much

159 higher activity in hydrothermal liquefaction than the lignite coal. From the results of co- liquefaction of lignin and lignite displayed in this figure, the total feedstock conversion is about 45 wt.%, which is approximately the average of those of XL (17.9 wt.%) and HL (70.0 wt.%). However, the HO yield (25.8 wt.%) is much higher than that of either lignite (10.7 wt.%) or lignin (17.8 wt.%). In general, during coal liquefaction, thermal decomposition of C-O-C or C-C bond in coal gives free radicals at around 350ᵒC. Then, the free radicals are stabilized by hydrogen from vapor phase or hydrogen donating substances such as ethanol/water solvent, which would increase the HO production. Consequently, the co-liquefaction of lignin and lignite promotes the heavy oil yield, i.e., there is a synergy effect in the co-liquefaction of lignin and lignite, which is consistent with the literature findings from co-liquefaction of low rank coals and lignocellulosic biomass [27,29,30].

5.41 HL & 25.77 54.30 14.51 Lignite

5.18

Lignite 10.65 82.12

2.05

Lignin 17.76 30.00 16.39 35.85

- 20 40 60 80 100 Yield (wt.%) HO SR WESO Gas+water

Figure 6-4 Products distribution during liquefaction of individual HL or XL, and co- liquefaction of HL and XL at 350ᵒC for 30 min without catalyst.

160

6.3.4 Co-liquefaction of lignin and lignite with catalyst

Fig. 6-5 displays products distribution during co-liquefaction of HL and XL with and without catalyst at 350C for 30 min and 400C for 2 h, respectively. The results as shown in this Figure demonstrate that the hematite and goethite are very active catalysts for co-liquefaction of XL and HL in particular at a higher temperature 400C, as similarly reported in our previous studies for hydrothermal liquefaction of peat [24]. It is also shown that hydrogen reduction of the hematite

(Fe2O3) or goethite (FeOOH) at 500C for 4 h drastically enhanced the HO yield at 400C for 2 h from 18.3 wt.% (without catalyst) to about 42 wt.% in the presence of either of these two reduced catalysts [31]. The metallic iron phase of the catalyst could be oxidized to form Fe3O4 during the co-liquefaction process, and the formed Fe3O4 could be reduced by hydrogen. Such redox behavior of the iron catalysts would promote both the hydrodeoxygenation process and the lignin and lignite hydrothermal degradation process, resulting in more HO yield [25,32,33].

According to Fig. 6-5, both hematite and goethite are effective catalysts for the co-liquefaction of lignin and lignite, which is consistent with the results reported in our previous studies for hydrothermal liquefaction of peat [24]. The goethite showed better performance than the hematite, but the reduced goethite and hematite exhibited almost the same activity with respect to HO yield, which implied that the catalytic active components would be the reduced iron species. As well known, goethite can be easily reduced to metallic Fe than hematite, so it explains that reduced goethite showed slightly better activity than hematite (Fe2O3). Fig. 6-5 also reveals that when using the reduced goethite and hematite as catalysts, a higher operating temperature and longer retention time, e.g. 400C and 2 h, are beneficial for their activity in co-liquefaction of HL and XL.

161

(a) 5.41 No-Catalyst 25.77 54.30 14.51 4.43 R-goethite 37.36 39.1 19.1 4.04 R-Hematite 37.8 45.53 12.62 3.8 Goethite 36.73 39.98 19.49 5.9 Hematite 27.73 47.68 18.68

0 20 40 60 80 100 Yield (wt.%) HO SR WESO Gas+water

(b)

No-Catalyst 18.3 43.5 13.43 24.77 3.63 R-goethite 42 35.27 19.1 3.99 R-Hematite 41.29 42.09 12.64 3.85 Goethite 37.6 40.79 17.77

Hematite 30.17 49.33 7.86 12.64

0 20 40 60 80 100 Yield (wt.%) HO SR WESO Gas+water

Figure 6-5 Products distribution during co-liquefaction of HL and XL with and without catalyst at 350ᵒC for 30 min (a), and 400ᵒC for 2 h (b).

XRD patterns of the raw hematite and the reduced hematite are presented in Fig. 6-6. After reduction, the intensity of the strong hematite peak at 2Ѳ = 33.28ᵒ reduces to 46% in the reduced

162

catalyst. It is hardly to observe any reduced iron species except magnetite Fe3O4 in the reduced hematite iron ore. As shown in Fig. 6-6, new iron oxide species i.e. Fe3O4 are observed in the reduced iron ore, although x-ray diffraction lines of metallic Fe species were not detected perhaps due to their high dispersion and low concentration, or because the reduced iron species on the surface of catalyst would be oxidized and react with the un-reduced Fe2O3 to form Fe3O4 when it was exposed to the air for the XRD analysis.

◊ Fe O 3 4 ◊ ● Fe2O3 ● ●

◊ ◊ ◊ ● ◊ ● ◊ ● ● ● ◊ ● ● b

● Intensity (a.u.) Intensity

● ● ◊ ● ● ● ●● ● a

10 30 50 70 2ɵ (deg.)

Figure 6-6 XRD patterns of the raw hematite (a) and the reduced hematite (b).

6.3.5 Characterization of the liquefaction products

6.3.5.1 Characterization of the feedstocks and solid residue from the co- liquefaction

The FT-IR spectra of the raw XL lignite coal, HL lignin and the spectra for the solid residue from the co-liquefaction (at 350°C for 30 min) are shown in Fig. 6-7. The strong absorption peak at 1040 cm-1 attributed to the stretching vibration of C-O ether group in HL and XL feedstocks is

163 much stronger than that in the solid residue from the co-liquefaction process, as expected due to the decomposition of the functional group during hydrothermal liquefaction. The strong absorption peaks at 1500-1700 cm-1 and 3200-3500 cm-1 can be attributed to the stretching vibration of C=C in aromatic group and hydroxyl group OH, respectively, in HL and XL. In addition to the band near 1600 cm-1, the IR bands 1500 cm-1 and 1450 cm-1 observed in HL can also assigned to aromatic ring C=C stretching vibration modes [34]. It is obvious that the IR intensity of the OH stretching for HL lignin is stronger than that for XL coal, and the solid residue is almost free of OH group, which is consistent with the higher oxygen content in HL compared with those of the XL coal and the solid residue (see Table 6-1). The bands between 3000 and 2800 cm-1 can be assigned to aliphatic C-H stretching vibration mode and used to measure the aliphatic hydrogen content [17,34,35]. The intensities of aliphatic C-H stretching mode of the lignin is higher than that of the XL coal or the solid residue.

164

SR from the co-liquefaction

HL lignin Transmittance (a.u.) Transmittance

XL lignite

3800 3400 3000 2600 2200 1800 1400 1000 600 Wavenumber (cm-1)

Figure 6-7 FT-IR spectra of the XL, HL and the SR from the XL/HL co-liquefaction at 350 °C for 30 min.

6.3.5.2 Characterization of HOs from the co-liquefaction

The gel permeation chromatograms (GPC) of HOs from co-liquefaction of XL coal and HL lignin over different catalysts and without catalyst are presented in Fig. 6-8. Weigh average (Mw) and number average (Mn) molecular weights of some HOs are calculated and presented in Table 6-3. Based on the GPC curves the average molecular weight and distribution of all HOs are similar, although the heavy oils produced in the presence of catalysts at 400C for 2 h have Mn

(194–198 g/mol), and Mw (330–342 g/mol), greater than those of the oil without catalyst (Mn =

171 g/mol and Mw = 278 g/mol). These results suggest that the presence of an iron catalyst, irrespective of hematite or goethite, in raw or reduced form, has insignificant effect on molecular weight and distribution of the resulting HO products.

165

0.45 0.4 0.35 0.3 0.25 0.2 HO-400ᵒC-2h

0.15 R-Goethite 400ᵒC-2h UV AbsorbanceUV 0.1 Goethite 400ᵒC-2h 0.05 Hematite 400ᵒC-2h R-Hematite 400ᵒC-2h 0 0 5 10 15 20 Elution time (min)

Figure 6-8 Gel permeation chromatograms of HOs from co-liquefaction of XL and HL at 400 ᵒC for 2 h without and with different catalysts.

The elemental composition (C, H, N, S, and O) as well as the average molecular weights (Mw and

Mn) of the HOs obtained at 400 C for 2 h with and without catalyst are comparatively showed in Table 6-3. The HOs are composed of 66 – 77 wt.% C, 7.9 – 8.7 wt.% H, 0.59 – 0.73 wt.% N, 12 – 25 wt.% O, and 0.73 – 0.85 wt.% S, and an HHV of 29– 36 MJ/kg, as presented in Table 6-3. The use of catalyst produced HO with greatly increased C content (from 66 to 77 wt.% C), reduced O content (from 24.7 wt.% to 12.5 wt.%) and hence increased HHV (from 29 to 36 MJ/kg), although the HOs obtained from this work contain less carbon and HHV and more oxygen compared with the oil products from co-liquefaction of Elbistan lignite and olive bagasse due to differences in feedstock and liquefaction conditions [36]. Considering the high O content in the HO products derived from co-liquefaction of XL and HL, the obtained HOs need further upgrading by hydrodeoxygenation before using as a fuel. However, as shown in Table 4-3, the HOs have an H/C molar ratio of 1.35-1.48, suggesting aromatic/phenolic structures, confirmed by the GC-MS

166

analysis (Table 6-4), the HOs from co-liquefaction of XL and HL may be used as phenol substitutes in the synthesis of bio-phenolic resins/adhesives [33].

Table 6-3 Chemical and physical properties of the HOs from co-liquefaction of HL and XL at 400ᵒC for 2 h without and with hematite or reduced hematite catalyst.

H/C HHVb M M HOs C H N S Oa w n PDI (-) (-) (MJ/kg) (g/mol) (g/mol)

No catalyst 65.89 8.10 0.59 0.73 24.70 1.48 29.41 299 153 1.95

Hematite 74.00 7.92 0.70 0.85 16.53 1.28 33.36 330 194 1.70

R-Hematite 77.28 8.67 0.73 0.84 12.48 1.35 36.25 334 196 1.70

a by difference; b Higher heating value (HHV) by the Dulong formula: HHV (MJ/kg) = 0.3383C

+ 1.422 (H - O/8).

Chemical compositions of the volatile fraction of the HO products were quantitatively characterized by GC-MS using Di-n-butyl ether as an internal standard. Fig. 6-9 shows GC-MS spectra for the selected HO products form the operation of co-liquefaction without and with catalyst at 400C for 2h.

167

Table 6-4 Concentration of low-Mw aromatics/phenolics in HOs from co-liquefaction of XL and HL at 400ᵒC for 2 h.

Aromatics/phenolics concentration (mg/g-HO)

No. Compounds name MW Goethite R-Goethite Hematite R-Hematite No catalyst

1 1,3,5-trimethyl benzene 94 0.63 0.25 0.93 - -

2 4-ethyl benzamine 108 0.45 0.44 0.17 0.81 -

3 Phenol 124 0.4 0.47 0.18 0.35 0.16

4 2-methyl phenol 108 - 0.52 0.19 - -

5 trimethyl phenol 122 0.88 1.08 0.51 0.13 0.4

6 2-ethyl phenol 122 0.74 0.1 0.41 1.18 0.13

7 2,5- methyl phenol (p-Xynelol) 108 0.58 0.91 0.33 0.83 0.18

8 2,3-methyl phenol (o-Xynelol) 136 1.32 1.54 1.61 2.03 0.43

9 ethyl-m-cresol 152 2.01 2.18 1.89 2.14 0.29

10 2,5-Diethyl phenol 110 1.96 1.83 1.51 2.22 0.23

11 2,4,5-trimethyl phenol 140 1.6 1.73 1.56 1.85 0.83

12 Thymol 150 3.23 2.44 2.05 2.06 0.84

13 2,3,5,6-tetramethyl phenol 124 - 3.14 2.31 3.47 1.19

Sum 13.81 16.63 13.64 17.06 4.68

168

The concentrations of the major aromatic compounds detected by GC-MS in HOs from co- liquefaction of XL and HL at 400C for 2 h are summarized in Table 6-4. Due to the limitation of GC-MS analytical technique (i.e., only low boiling point volatile compounds can pass the GC column for detection) and the complexity of chemical composition of tars (containing a great number of high boiling point compounds), normally only about 10-40% of mass of a bio-oil could be detectable by GC-MS [37]. By comparing the GC-MS results for HOs with and without catalyst, it can be seen that co-liquefaction in the presence of catalyst, specially an in-situ reduced catalyst, produced much more low Mw monomeric aromatic/phenolic compounds (4.68 mg/g-HO without catalyst vs. 13.6 ~ 17.1 mg/g-HO with a catalyst), which is in a good agreement with the lower H/C molar ratios for the HOs with a catalyst than that of the oil without catalyst (Table 6-3). As also shown in Table 6-4, when compared with the un-reduced catalysts, the in-situ reduced catalysts produced HOs with much more monomeric aromatic/phenolic compounds in co- liquefaction of XL and HL at 400C for 2 h. Thus, the HOs from co-liquefaction of XL and HL may be used to substitute phenol for producing bio-based phenolic resins as bonding agents and adhesives [33, 34].

169

Absorbance No Catalyst

7 10 9 12 13 R-Hematite 6 8 11 1 23 4 5

2.5 4.5 6.5 8.5 10.5 12.5 Elution time (min)

Figure 6-9 GC-MS spectra of the HO products from co-liquefaction of XL and HL at 400 ᵒC for 2 h.

6.4 Conclusions

In this study, effects of iron-based catalysts (hematite iron ore and synthetic goethite with/without reduction) in co-liquefaction of HL lignin and XL lignite coal in ethanol-water (1:1 v/v) mixed solvent were investigated experimentally at temperatures ranging from 350C to 435C for varied length of residence time from 30 min to 2 h. The following conclusions may be drawn:

(1) Hematite iron ore (consisting mainly of hematite (Fe2O3) and goethite (FeOOH)), in either reduced or un-reduced form, was found to be extraordinarily active for promoting heavy

oil (HO) yield. At 400C for 2 h, addition of the H2-reduced hematite ore dramatically

170

enhanced co-liquefaction process and produced heavy oil (HO) at a high yield close to 42 wt.%, almost doubling that of the operation without catalyst.

(2) The results demonstrated a positive synergy effect on HO yield during co-liquefaction of the HL lignin and XL lignite coal.

(3) Co-liquefaction of HL and XL in the presence of catalyst, specially an in-situ reduced

catalyst, produced much more low Mw monomeric aromatic/phenolic compounds. The HOs from the co-liquefaction may be used to substitute phenol for producing bio-based phenolic resins as bonding agents and adhesives

(4) The use of catalyst produced HO with greatly increased C content, reduced O content and hence increased HHV.

6.5 Acknowledgments:

The financial support for this work was provided mainly through the NSERC Discovery Program, NSERC/FPInnovations Industrial Research Chair Program in Forest Biorefinery, and BioFuelNet. This work was also partially supported by the National Science Foundation of China (Grants # 21476003, and 21776001).

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[38] Z. Du, X. Ma, Y. Li, P. Chen, Y. Liu, X. Lin, H. Lei, R. Ruan, Production of aromatic hydrocarbons by catalytic pyrolysis of microalgae with zeolites: Catalyst screening in a pyroprobe, Bioresour. Technol. 139 (2013) 397–401. doi:10.1016/j.biortech.2013.04.053.

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Chapter 7

7 Bio-phenol formaldehyde (BPF) resoles prepared using phenolic extracts from the biocrude oils derived from hydrothermal liquefaction of hydrolysis lignin

176

Abstract:

In this work, biocrude oils were produced by hydrothermal liquefaction (HTL) of hydrolysis lignin (HL) in water-ethanol (50:50, v/v) mixture with and without hematite ore as the catalyst. A neat phenol formaldehyde (PF) resole and four bio-phenol formaldehyde (BPF) resoles were prepared using whole biocrude oils and the phenolic extracts (PE) from the oils to substitute 50% of phenol. The results displayed that although the BPF resoles contain a higher free formaldehyde and less thermally stable than the neat PF resole, they could be cured at a lower temperature when compared with the neat PF resole. More importantly, all BPF resoles demonstrated to be suitable adhesives for plywood bonding. The dry and wet boning strengths for all BPF resoles meet and exceed the minimum requirements in accordance to the JIS standard. The dry bonding strengths of BPF resoles prepared with the phenolic extracts are higher than that of the BPF resoles prepared with the whole biocrude oils and the neat PF resole. The superior performance of the phenolic extracts from the HTL biocrude oils can be attributed to the lower molecular weights and enriched phenolic compositions of the phenolic extracts.

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7.1 Introduction

Currently, the raw materials used in the production of synthetic adhesives are primarily petrochemicals or their derivatives. The synthetic adhesives i.e. phenol formaldehyde (PF) resole and urea formaldehyde resole are the most expensive components in the production of engineered wood panels such as plywood, OSB, particleboard, etc. PF resoles are the alkali catalyzed polycondensation products from phenol and formaldehyde with an F/P molar ratio > 1.0. Due to the high cost of using phenol as the raw material and the fact that it derives from benzene - a non- renewable petroleum-based chemical through the cumene hydroperoxide route in industry, a number of studies in different countries have been carried to search cheaper as well as viable phenolic substitutes. To achieve this goal, a variety of renewable phenol alternatives and their derivatives such as lignin [2–4], tannin [5–8], and barks [9,10] have been investigated to replace petroleum-based phenol in the production of PF resins.

Lignin is the second most abundant polymer from lignocellulosic biomass and is a high molecular weight polymer composed of methoxylated alkylphenol units. Technical lignin can be isolated from wood, annual plants, i.e. agricultural residues by different extraction/pulping processes. Lignin is an amorphous three-dimensional phenyl-propanol polymer of three phenyl-propanols i.e., p-coumaryl alcohol (p-hydroxyl-phenyl-propanol), coniferyl-alcohol (guaiacyl-propanol) and sinapyl-alcohol (syringyl-propanol) [11], and it has been regarded as a rich source of phenols. However, since lignin has a random three-dimensional network with severe steric hindrance effects, it has relatively lower reactivity when using as bio-phenols for chemical synthesis. Accordingly, although many reports have announced the development of bio-phenol formaldehyde (BPF) adhesives using woody or agricultural lignin, the major challenge of substituting lignin for phenol is the fact that lignins as bio-phenols are less reactive due to the lack of reactive sites for the addition reactions with formaldehyde in the synthesis of BPF resins [12].

Various methods for the production of bio-phenols with lower molecular weights and hence improved reactivity from lignin have been studied, such as pyrolysis [13,14], catalytic cracking [15,16], and hydrothermal liquefaction (HTL) [17,18]. Recently, HTL of lignocellulosic materials has been received much attention for obtaining bio-phenols for phenolic resin production. It usually operates under high pressure at temperatures lower than 350 ᵒC in hot-compressed water

178 media (with or without some organic solvent), producing liquefaction oils, and commonly called biocrude oils. In a study by Tajedo e al. [19], biocrude oils from three different lignins (kraft pine lignin, soda-anthraquinone flax lignin, and ethanol-water wild tamarind lignin) were compared for their activity in the synthesis of BPF resins. Birocrude oils from kraft pine lignin demonstrated to be the best phenol substitute among others from various lignins. In an another work, effects of rubidium (Rb) and caesium (Cs) as catalysts on HTL of wood biomass at 280 ᵒC for 15 min for production of bio-phenols were investigated by Karagoz et al. [20]. In a previous study by the authors [21], HTL of lignocellulosic wastes of sawdust and cornstalks and two model biomass compounds (pure lignin and pure cellulose as references) was investigated at 250-350 ᵒC under the initial pressure of 2 MPa in hot-compressed water. It was showed that the relative concentration of phenolic compounds in the lignin-derived oil reached 80% of the volatile fraction of the oil based on gas chromatography-mass spectroscopy (GC-MS) analysis. In an another studies in our group [22], bark liquefaction in hot compressed water/ethanol (50:50, v/v) mixture contributed to very high yields of biocrude oils and the bark derived biocrude oils are rich in phenolic compounds, which makes it a suitable substitute for phenol in BPF resoles synthesis.

Thus, HTL of lignocellulosic biomass or lignin is a promising pathway to produce phenolic biocrude oils as bio-phenols for the synthesis of BPF resoles at a greater phenol substitution ratio. In a previous work by the authors’ group [23], biocrude oil derived from Eastern white pine (PinusStobus L.) sawdust in hot compressed water/ethanol (50:50, v/v) mixture could substitute 50-75 wt.% of phenol in BPF resole synthesis and the resultant BPF resoles showed comparable chemical and curing properties and dry/wet bonding strengths for their application as plywood adhesives.

On the other hand, various tranistion metals (Ni, Fe, etc.)-based calyats proved to be effective for propdcing high-quality phenolic biocrude oils, e.g., with reduced lower Mw in HTL of lignocellulosic biomasss [24, 25]. Hydrolysis lignin (HL) is a by-product generated from cellulose hydrolysis for the production of sugar as feedstock for bio-fuels (bio-ethanol/butanol) and biochemicals. FPInnovations has developed and patented the TMP-BioTM process to produce sugars from hardwood, which generates HL by-product [26]. Valorizing the HL by-product for high-value bio-based chemicals/materials is critically important for the overall economics of the TMP-BioTM process. Therefore, the present work aimed to synthesize BPF resoles as wood adhesives using

179 bio-phenols from HTL of HL with or without an inexpensive iron-based catalyst (hematite ore), and to investigate the comparative properties of BPF adhesives using the phenolic extracts separated from the biocrude oils and whole biocrude oils.

7.2 Materials and methods

7.2.1 Materials

Hydrolysis lignin (HL) used in this study was provided by FPInnovations, Canada, derived from Aspen wood in its pilot TMP-BioTM process. As shown in Table 7-1, the HL contains 50-60 wt% lignin balanced by the residual carbohydrates (cellulose and hemicellulose), ash and others, but the molecular weight of the HL was not measurable due to its insolubility in a suitable solvent. Elemental composition the HL are also presented in Table 7-1. Anhydrous ethyl alcohol (ethanol), ethyl ether, and acetone (≥99.5%) were purchased from Caledon Laboratory Chemicals, Canada. ACS reagent grade formaldehyde (37% aqueous solution) and sodium hydroxide solution (50% aqueous solution) were purchased from EMD, Germany. ACS reagent grade sulfuric acid solution (≥98.0%) was purchased from VMR, USA. Phenol (≥99.0%) was provided by Sigma-Aldrich.

Table 7-1 Elemental composition and chemical contents of hydrolysis lignin.

Elemental composition (wt.%, d.a.f.1) Chemical components (wt.%, d.b.2)

3 C H N O Lignin Carbohydrates Ash Others

49.76 6.45 0.33 43.46 56.7 29.8 1.2 12.3 1 Dry and ash free.

2 On a dry basis.

3 Determined by the difference.

The HTL catalyst used in this work was hematite ore obtained from a mine in Ma’anshan, Anhui, China. The raw hematite ore was characterized with X-ray fluorescence (XRF), and the XRF

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results are shown in Table 7-2. The raw hematite is mainly composed of 91.7±0.1 wt.% Fe2O3 and

3.7±0.1 wt.% SiO2 and 3.1±0.1 wt.% Al2O3.

Table 7-2 XRF analysis of the raw hematite ore.

Compound wt. % Element wt. %

Fe2O3 91.7±0.1 Fe 64.2±0.1

SiO2 3.6±0.1 Si 1.7±0.0

Al2O3 3.1±0.1 Al 1.6±0.1

MnO 0.4±0.0 Mn 0.3±0.0

K2O 0.3±0.0 K 0.3±0.0

P2O5 0.2±0.0 Px 0.1±0.0

MgO 0.2±0.0 Mg 0.1±0.0

CaO 0.2±0.0 Ca 0.1±0.0

TiO2 0.1±0.0 Ti 0.1±0.0

Others 0.1±0.0 Others 0.1±0.0

7.2.2 Methods

7.2.2.1 Preparation of Biocrude-oil with and without catalyst

Hydrothermal liquefaction experiments were performed in a 500 mL stirred reactor. In a typical run, 30.0 g of HL was loaded into the reactor with 300.0 mL water-ethanol (1:1 v/v) mixture together with 6.0 g of catalyst (20 wt.% of HL by weight) for the catalytic HTL process. The reactor was then sealed and the residual air inside the reactor was removed by N2 purging- vacuuming for at least five times, followed by pressurizing the reactor to 2 MPa using nitrogen. The reactor was heated at 10 ᵒC/min to 350 C under 600 rpm stirring. Due to the water-ethanol vapor pressure, the reactor pressure increased during the temperature elevation to 350C, at which the average pressure inside the reactor during the HTL was approx. 22.0 MPa. In this study, the

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HTL operating condition was fixed at 350C for 30 min, based on the previous studies by the authors’ group [22, 23]. Then the reaction was stopped by quenching the reactor in a water/ice bath. Once the reactor was cooled to room temperature, the gas inside was released into a gas-bag, then the reactor was opened, and the solid/liquid products were rinsed with reagent grade acetone to completely remove the ethanol-water insoluble materials including heavy oils and the residual chars adhering on the inner wall of the reactor by scraping with a spatula. The slurry and rinsing acetone were collected and filtered under vacuum. The total solid residue was rinsed with acetone until the resulting filtrate became colorless. The filtrate was then evaporated under reduced pressure to completely remove acetone at 45C, and the dark color oily product was weighed and denoted as biocrude oil. The abovementioned non-catalytic and catalytic HTL operations resulted in biocrude oil products in approx. 54% and 42% yield, respectively.

7.2.2.2 Preparation of phenolic extracts from biocrude-oils

To separate phenolic extracts from biocrude oils, the HL-derived oil was first mixed with sodium hydroxide solution to form a dark colored mixture with pH of 12-13. The mixture was then transferred into a separatory funnel with ethyl ether (EE). A first extract removed from the separatory funnel consisted of the neutral fraction of the oil, which was subjected to distillation process to remove the solvent and recover the neutral extract (mainly contains aromatic and long- chain hydrocarbon fractions of the HTL-oils). Then, the raffinate from the first extraction was adjusted to pH to 4.0-5.0 using sulfuric acid, before it was introduced into the second extraction stage in a separatory funnel, where it was contacted with EE solvent. In this extraction step the phenolic extract was removed with the solvent, which was distilled to recover the solvent and the phenolic extract. The resulted EE insoluble oil was denoted as insoluble residue. The entire extraction procedure is shown in Fig. 7-1. The extraction led to 29% and 27% neutral extract yield, 7% and 12% phenolic extract yield, and 64% and 62% insoluble residue yield with the non- catalytic HTL-oil and the catalytic HTL-oil, respectively. In this work, the whole biocrude oils from the non-catalytic HTL and the catalytic HTL operations, and the corresponding phenolic extracts are denoted as Biocrude, C-Biocrude, PE-Biocrude and PE-C-Biocrude, respectively.

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Molecular weights and polydispersity index (PDI) of the whole biocrude oils from the non- catalytic HTL and the catalytic HTL operations, as well as the phenolic extracts from these two biocrude oils were determined with a water Breeze GPC-HPLC instrument (1525 binary lamp, UV detector set at 270 nm, waters Styragel HR1 column at 40ᵒC) using tetrahydrofuran (THF) as the eluent and linear polystyrene standards for the molecular weights calibration.

The chemical structures of the two whole biocrude oils and the phenol extracts derived from the biocrude oils were investigated by Fourier transform infrared spectroscopy (FTIR). The FTIR spectra were collected on a Perkin Elemer FTIR by scanning the biocrude oils or phenol extracts at the resolution of 4 cm−1 from 4000 cm−1 to 550 cm−1.

Figure 7-1 Extraction procedure for separation of phenolic extract from the biocrude oil.

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7.2.2.3 Synthesis and characterization of bio-phenol formaldehyde (BPF) using whole biocrude oils or phenolic extracts from the biocrude oils

Formaldehyde/phenol molar ratio of 1.8/2.6 was applied for the PF/BPF resole synthesis. In this study, neat PF resole was first synthesized as the control in the following procedure: 10.0 g phenol, 10.0 g water and 3.0 g 50% NaOH solution were first charged into a 150 mL three- neck reactor connected to a refluxing condenser. The mixture was stirred and heated to 65ᵒC. During the heating process, 15.5 g 37% formaldehyde was added into the reactor drop-wise. The reactor was maintained at 65ᵒC for 60 min, then the temperature was increased to 85ᵒC and the reactor was kept at 85ᵒC for 120 min, finally it was cooled down in a water/ice bath. The obtained viscous resin product was designated as neat PF resole.

For the BPF resoles synthesis with 50% phenol substitution ratio, the whole biocrude oils from the catalytic/non-catalytic HTL and the obtained phenolic extracts were respectively used in the synthesis in the following procedure: 5.0 g of biocrude oil or phenolic extract, 10.0 g water and 3.0 g 50% NaOH solution were charged into a 150 mL three neck glass reactor. The mixture was heated to 80ᵒC and hold at 80ᵒC under stirring for 30 min. After cooling down, 5 g phenol was added to the reactor then the mixture was stirred and heated to 65ᵒC. During the heating process, 15.5 g 37% formaldehyde was added into the reactor drop-wise. The reactor was maintained at 65ᵒC for 60 min, then the temperature was increased to 85 ᵒC and the reactor was kept at 85ᵒC for 120 min, finally the reactor was cooled down in a water/ice bath. The obtained 4 BPF resoles employing the whole biocrude oils from the non-catalytic HTL and from the catalytic HTL, the phenolic extracts from the non-catalytic HTL biocrude oil and from the catalytic HTL biocrude oil were designated as 50% BPF resole, 50% C-BPF resole, 50% PE-BPF resole, and 50% PE-C-BPF resole, respectively.

Basic characterizations (e.g., pH, viscosity, solid content, free formaldehyde content) were carried out on all the synthesized resoles. pH values were measured with a pH meter (Thermo Scientific, Orion2 Star pH Benchtop) at room temperature. Viscosities were tested using a Brookfield CAP 2000+ viscometer (Brookfield Engineering Laboratories, Middleboro, MA) at 50ᵒC. Solid contents were determined by drying the resoles at 125ᵒC for 105 min. Free formaldehyde contents in the resoles were determined using a modified Walker’s hydroxylamine hydrochloride method

184 in accordance to EN ISO 9397 standard (1997). Specifically, 2.0 g resole was dissolved in 50 mL isopropanol/water (3:1, v/v) mixture in a 250 mL beaker at 23ᵒC. pH value of the solution was adjusted to 3.5 by adding 1.0 mol/L hydrochloric acid, then approximately 25 mL hydroxylamine hydrochloride solution (10 wt.%) was added. After 10 min stirring, the solution was titrated rapidly using 1.0 mol/L sodium hydroxide solution to pH 3.5. A blank test without any resole sample was also conducted in parallel. Free formaldehyde content in resole was calculated from equation (7- 1).

퐶(푉₁−푉₀) 퐹푟푒푒 푓표푟푚푎푙푑푒ℎ푦푑푒 푐표푛푡푒푛푡 (%) = 3 × (7-1) 푚

Where:

C: The real concentration (mol/L) of the used sodium hydroxide solution.

V0: The volume (mL) of sodium hydroxide solution used in the blank test.

V1: The volume (mL) of sodium hydroxide solution used in the test for the resole sample.

m: The weight (g) of the resole used for the test.

Gel Permeation Chromatography (GPC) was used for measuring the molecular weights and distributions for the resoles. Since the resoles have poor solubility in THF, they were acetylated before GPC measurements in the following procedure: 0.5 g resole sample was dissolved in 10 mL of pyridine/acetic anhydride (5:5, v/v) mixture and stirred at room temperature for 24 h. The acetylated PF resole was precipitated in 1.0 wt.% icy HCl solution, filtered and rinsed thoroughly with distilled water, followed by vacuum drying at 50ᵒC for 24 h. For the GPC measurement, the dried acetylated resole was dissolved in THF (0.1 wt.%), following the same procedure for the GPC measurements with biocrude oils. FTIR was also employed to characterize the chemical structure of the resoles (pre-cured at 125ᵒC for 105 min).

The curing properties of the resoles were tested by differential scanning calorimetry (DSC, Mettler Toledo, Stare System) using the non-isothermal method at varying heating rates. Briefly, 10 mg vacuum dried resole sample was loaded into an aluminum crucible and heated in 50 mL/min N2 flow from 40ᵒC to 200ᵒC at specified heating rates of 2.5 ᵒC/min, 5.0 ᵒC/min, 7.5 ᵒC/min and 10.0

185

ᵒC/min, respectively. Thermal stability of the PF resoles was characterized by thermogravimetric analysis (TGA, Pyris 1 TGA, Perkin Elemer). Before the TGA tests, the resoles were pre-cured at 125ᵒC for 105 min. In each TGA run, 10 mg pre-cured resole was loaded into a platinum pan and heated from 50ᵒC to 800ᵒC at 10ᵒC/min in 20 mL/min N2 flow.

In addition, to examine the performance of the resoles as wood adhesives, 3-ply plywood specimens were prepared from yellow birch veneers. Before plywood preparation, the veneers (11 × 11 × 1/16 in.3) were conditioned at 20ᵒC and 65% relative humidity for 15 days. The synthesized resole was applied by brushing uniformly on the surface of the conditioned veneers in an amount of 250 g/m2. The face and center veneer were then bonded in directions perpendicular to each other by hot-pressing under 10.0 MPa pressure at 150ᵒC for 4 min. Mechanical properties of the bonded plywood were measured by tension shear strength tests (i.e., tests for shear strengths by tension loading). Specimens for the tests were cut in accordance with ASTM D 906-98 (Reapproved 2011). One half of the specimens bonded by the same resole were tested after being conditioned at 20ᵒC and 65% relative humidity for 7 days for dry strength, while the other half were soaked in boiling water for 3 h for wet strength tests. The shear strength of 3-plywood specimens was measured by tension loading on a bench-top universal testing machine (ADMET eXpert 7603 eP2 Universal Testing System) at the loading rate of 3 mm/min till failure.

7.3 Results and discussion

7.3.1 Basic characterization of the BPF resoles

Basic properties of neat PF resole and the four BPF resoles are displayed in Table 7-3. pH values of all resoles (pH 10.46–11.26) are almost the same due to the base catalyzed synthesis condition of the resoles. Solid content of neat PF resole is 44.2%, slightly higher than that of BPF resoles (37.7–42.7%), likely due to the presence of low-boiling point compounds in the biocrude oils or the phenolic extracts, as similarly observed in some previous studies on barked–derived BPF resoles [9, 10]. The viscosity of the neat PF resole at 50ᵒC is 26.5 cP, while viscosities of all the BPF resoles (except for 50% BPF) are lower (13.1-20.6 cP), likely due to the lower solid content for the obtained BPF resoles, as described above.

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Table 7-3 pH, solid content, viscosity and free formaldehyde content of all resoles.

Free Solid Content Viscosity at 50 ᵒC formaldehyde PH (wt%) (cP) content (%) Neat PF 10.46(0.02) 44.2(0.01) 26.5(0.01) 0.34(0.02)

50% BPF 10.62(0.04) 42.7(0.00) 33.2(0.01) 0.91(0.01)

50% C-BPF 10.48(0.00) 39.1(0.00) 13.1(0.06) 0.88(0.03)

50% PE-BPF 11.02(0.01) 39.1(0.01) 20.6(0.07) 0.76(0.02)

50% PE-C-BPF 11.26(0.02) 37.7(0.01) 18.6(0.10) 0.65(0.01)

However, the free formaldehyde content in the neat PF resole (0.34%) is much lower than that in any a BPF resole, which is attributed to the relatively lower reactivity of bio-phenols (bio-oils or phenol extracts) towards formaldehyde delaying the addition reaction during the BPF resole synthesis due to the facts that the bio-phenols have larger molecular weights (as evidenced in our GPC analysis results given in Table 7-4) and hence greater steric hindrance of their molecules [9, 10, 27]. Free formaldehyde content in these BPF resoles follows an order of 50% PE-C-BPF resole (0.65wt%) <50% PE-BPF resole (0.76wt%) <50% C-BPF resole (0.88wt%)<50% BPF resole (0.91wt%). The relatively lower free formaldehyde content in two phenol extracts-based BPF resoles, compared with the two whole biocrude-based resoles, could be attributed to the the lower molecular weights and presence of enriched phenolic compounds (more reactive toward formaldehyde) in these two phenol extracts (as evidenced by the GPC and FTIR analysis results, presented in Table 7-4 and Fig. 7-3, respectively) [9, 22][28].

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7.3.2 Molecular weight and chemical structures of the BPF resoles and the bio-phenols

Molecular weights and poly dispersity indexes (PDI) of the BPF resoles in comparison with the neat PF resole and various bio-phenols (the Biocrude, C-Biocrde, PE-Biocrude and PE-C- Biocrude) are displayed in Table 7-4. Molecular weights of all BPF resoles are greater than that of the neat PF resole, likely due to the larger molecular weights of the bio-phenols used in the resole synthesis. As shown in the Table, the weight average molecular weight (Mw) of bio-phenols are in the range of 780-1630 g/mol, 7-16 times larger than that of phenol (94 g/mol). Among the four bio-phenols used, PE-Biocrude and PE-C-Biocrude have a much lower Mw (780 g/mol and

960 g/mol, respectively) compared with the two whole biocrude oils (Mw =1380 g/mol and 1630 g/mol, respectively), which could account for the higher reactivity of the phenol extracts in the resinification reactions with formaldehyde, resulting in lower free formaldehyde contents in these two phenol extracts-based BPF resoles (Table 3). In addition, as clearly shown in the Table, all BPF resoles have a higher molecular weight than the corresponding bio-phenol, which confirms the polymerization reactions among the bio-phenols, phenol and formaldehyde during the resinification process.

Table 7-4 Molecular weights and PDI of the BPF resoles and bio-phenols.

Mn (g/mol) Mw (g/mol) PDI=(Mw/Mn)

Neat PF resole 440 730 1.66

50% BPF resole 1390 9720 6.99

50% C-BPF resole 1250 6810 5.45

50%PE-BPF resole 760 2110 2.77

50%PE-C-BPF resole 510 1850 3.63

Biocrude-oil 610 1630 2.67

C-Biocrude-oil 590 1380 2.34

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PE-Biocrude-oil 340 960 2.82

PE-C-Biocrude-oil 260 780 3.00

The IR spectra of the neat PF resole and all BPF resoles are shown in Fig. 7-2. The neat PF resole and all the BPF resoles display similar IR absorbance profiles, which indicates that BPF resoles have similar chemical structure to the neat PF resole. All the spectra display a strong broad band of -OH stretching at the wavelength of 3600–3200 cm−1, attributed to the presence of OH groups in the resoles such as phenolic group. All resins have C-O stretching (such as methylol (CH2OH) group) between 1000 - 1033 cm-1, and aromatic rings at 1600-1700 cm-1 [29]. The medium −1 -1 absorbance at 1448 cm and 1481 cm can be assigned to the bending of CH2, indicating the existence of methylene bridge in all the pre-cured resoles.

Ar-CH Aromatics rings C-O 50% PE-C-BPF resole -CH2-

50% PE-BPF resole -OH

50% C-BPF resole

50% BPF resole

Neat PF resole

500 1000 1500 2000 2500 3000 3500 4000 Wavelength (cm⁻¹)

Figure 7-2 FTIR spectra of neat PF resole and all the BPF resoles.

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Moreover, all bio-phenols (the two whole biocrude oils and the two corresponding phenolic extracts, i.e., Biocrude, C-Biocrude, PE-Biocrude and PE-C-Biocrude) were analyzed by FTIR, as illustrated in Fig. 7-3. The strong absorption peaks between 1600-1700 cm-1 and 3200-3600 cm-1 can be attributed to the stretching vibration of C=C in the aromatic group and hydroxyl group OH, respectively. As indicated in the Figure, the intensity of these peaks are much stronger in the phenol extracts compared with those in the whole biocrude oils. This result indicates the extraction process employed could effectively produce phenolic feedstocks with enriched content of phenolic compounds, which again explain the higher reactivity of the phenol extracts in the resinification reactions with formaldehyde, resulting in lower free formaldehyde contents in these two phenol extracts-based BPF resoles (Table 7-3).

Biocrude oil

PE-Biocrude-oil

C-Biocrude-oil

PE-C-Biocrude-oil

600 1100 1600 2100 2600 3100 3600 Wave Number (cm⁻¹)

Figure 7-3 FTIR spectra of the whole biocrude oils and the phenol extracts.

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7.3.3 Thermal stability and curing properties

The DSC profiles for curing of neat and all the BPF resoles at various heating rates ranging from 2.5 C/min to 10 C/min are shown in Fig. 7-4. As illustrated, all the resoles shows characteristic exothermic peak for condensation and crosslinking reactions (indicated by exothermic peaks) at 127-163 ᵒC.

Neat PF resole 10.0 ᵒC/min

7.5 ᵒC/min

5.0 ᵒC/min Heating Value (w/g) Value Heating 2.5 ᵒC/min

100 110 120 130 140 150 160 Temperature (ᵒC)

50% BPF resole

10.0 ᵒC 7.5 ᵒC

5.0 ᵒC Heating (W/g) Heating value 2.5 ᵒC

100 110 120 130 140 150 Temperature (ᵒC)

191

50% C-BPF resole 10.0 ᵒC

7.5 ᵒC

5.0 ᵒC

Heating (W/g) Heating value 2.5 ᵒC

80 100 120 140 Temperature (ᵒC)

50% PE-BPF resole

10.0 ᵒC/min 7.5 ᵒC/min

5.0 ᵒC/min Heating Value (W/g) Value Heating

2.5 ᵒC/min 100 110 120 130 140 150 Temperature (ᵒC)

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50% PE-C-BPF resole

10.0 ᵒC/min 7.5 ᵒC/min

Heating (W/g) Heating value 5.0 ᵒC/min 2.5 ᵒC/min

110 120 130 140 150 160 170 Temperature (ᵒC)

Figure 7-4 DSC profiles of neat PF resole and BPF resoles heated at various rates.

The broad exothermic peak for each resole is attributed to combination of various curing reactions including the condensation of free phenol or bio-oil with methylol groups (-CH2OH) to form a methylene linkage and the condensation of two methylol groups to form dibenzyl ether linkage and also dehydration of the dibenzyl ether to from methylene. In some of the resoles (e.g., 50% C- BPF resole and 50% BPF at some heating rates), the condensation peak is not so distinct. The exothermic peak temperatures for all resoles under various heating rates are summarized in Table 7-5. As given in the Table, the substitution of phenol with a bio-phenol (whole biocrude-oils or phenol extracts, except for the phenol extract from the catalytic HTL oil) into PF resole shifts the peak curing temperature to a lower value, suggesting that the large molecules of phenolic components derived from lignin in the BPF resoles could cure more readily at a lower temperature [9, 10] [29]. However, the presence of phenol extract from the catalytic HTL oil retards the curing process for the PE-C-BPF resole by shifting the peaks curing temperature to higher values, probably due to the lower reactivity of this bio-phenol.

By employing a multiple heating rate method, the curing kinetics of the PF resoles can be examined. Based on the curing peak temperatures as summarized in Table 7-5, the curing kinetic parameters were calculated from Kissinger Eq. (7-2) and Crane Eq. (7-3):

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훽 푑푙푛 ( 2 ) 푇푝 퐸 Kissinger Equation: 1 = − (7-2) 푑( ) 푅 푇푝

푑푙푛 (훽) 퐸 Crane Equation: 1 = − (7-3) 푑( ) 푛푅 푇푝

β: heating rate (K/min).

Tp: the peak temperature (K) in the DSC profile.

E: activation energy (kJ/mol).

N: the reaction order.

R: gas constant (=8.314 J/mol/K).

E/R and the reaction order (n) were directly evaluated from the slope of the regression line of the

2 working plots of ln(β/Tp ) and ln(β) versus 1000/Tp, respectively, as displayed in Fig. 7-5. The obtained thermal curing kinetic parameters for all resoles are listed in Table 7-5.

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Table 7-5 Thermal curing kinetic parameters for the resoles.

Heating Rate a b (K/min) Tp(K) E(kJ/mol) n Neat PF resole 2.5 410.27 99.62 0.93

5 418.08

7.5 421.04

10 429.67

50%BPF resole 2.5 400.22 121.65 0.95

5 408.61

7.5 412.02

10 415.15

50%C-BPF resole 2.5 409.67 119.93 0.95

5 413.94

7.5 419.85

10 424.89

50% PE-BPF 2.5 406.10 136.42 0.95 resole 5 411.51

7.5 414.66

10 420.05

50% PE-C-BPF 2.5 420.22 124.79 0.95 resole 5 428.46

7.5 433.78

10 435.61

a Based on the Kissinger equation.

b Based on the Crane equation.

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The activation energy for the neat PF resole curing was determined to be 99.62 kJ/mol and for the BPF resoles: 50% BPF, 50% C-BPF, 50% PE-BPF and 50% PE-C-BPF resoles, the activation energy increases to 121.65, 119.93, 136.42, 124.79 kJ/mol, respectively. The increased activation energy in all BPF resins suggests that the presence of large molecules of phenolic components derived from lignin decreases the curing speed of the BPF resoles, although enabling the curing of the BPF resoles at a lower temperature, as indicated by the reduced curing peak temperatures (Fig. 7-4 and Table 7-5). The higher curing activation energy of the BPF resoles might be due to the larger molecular weights, stronger steric hindrance and less reactivity of the bio-phenols [9, 10] [29]. The curing reaction order values, n, for all resoles is close to 1.0, suggesting first-order for the curing PF or BPF resoles curing reactions, which is in a good agreement with our previous findings [9].

-9.4 R² = 0.959 -9.6 R² = 0.9314R² = 0.9394 R² = 0.9928 Neat PF resole -9.8 R² = 0.9902 50% BPF resole -10 50% C-BPF resole 50%PE-BPF resole

Tp² -10.2 50% PE-C-BPF resole

β)/ -10.4 ln( -10.6 -10.8 -11 -11.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55 1000/Tp

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R² = 0.9456 2.5 R² = 0.9398 R² = 0.9628 R² = 0.9912 R² = 0.9935

β) ln( 1.5 Neat PF resole 50% BPF resole 1 50% C-BPF resole 50% PE-BPF resole 50% PE-C-BPF resole 0.5 2.25 2.3 2.35 2.4 2.45 2.5 2.55 1000/Tp

2 Figure 7-5 Linear plots of ln(β/Tp ) vs 1000/Tp and ln(β) vs 1000/Tp for all resoles based on the DSC measurements.

The thermal stability of the resoles were characterized by TGA. The TGA and differential thermogravimetry (DTG) profiles of all pre-cured resoles are illustrated in Fig. 7-6. Residual weight at 800ᵒC for the neat PF is about 55 wt.%, and it varies from 32 wt.% to 47 wt.% in BPF resoles. The lower weight residue for the BPF resoles indicate that they are less thermally stable compared to the neat PF resole, as similarly reported for other bio-based PF resins [9, 10]. The lower thermal stability of the BPF resoles might be due to some less stable component of the biocrude oils or phenolic extracts, e.g., the side alkyl phenol groups in bio-phenols could decompose at elevated temperature [30]. The mass loss of BPF resoles and the neat PF resole below 200 ᵒC could result from further condensation reactions and additional crosslinking or condensation reactions removing water. At 200-600ᵒC, fast decomposition of the BPF resoles, indicated by the mass loss peaks (DTG bottom peaks) occurred (peaked) at temperatures 380- 480ᵒC, compared with 520ᵒC decomposition peak for the neat PF resole. These decomposition peaks likely resulted from thermal decomposition of the bridge of methylene linkage [9, 10]. For all resoles, decomposition peaks at >700ᵒC were observed, which could be due to the cracking of

197 the condensed ring network of the resins. In conclusion, as described before in the DSC analysis, substitution of phenol with biocrude oils or phenolic extracts from the biocrude oils resulted in BPF resoles with decreased thermal stability, typical for almost all bio-based PF resins as reported in the literature [9, 10, 29].

100 0.3

90 0.2 80

Neat PF resole 70 50% BPF resole 0.1 50% C-BPF resole 60 50% PE-BPF resole 50% PE-C-BPF resole 50 0

Weight Residue (%) Residue Weight Derivatives (%/min) Derivatives -0.1 30

20 -0.2 10

0 -0.3 0 200 400 600 800 Temperature (ᵒC)

Figure 7-6 TG and DTG profiles of the BPF and PF resole resins.

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7.3.4 Bonding performance of the BPF resoles as wood adhesives

The tensile strengths of the 3-ply plywood specimens bonded with a BPF or neat PF resole resin are illustrated in Fig. 7-7.

3.50 Dry strength Wet strength 3.00

2.50

2.00

1.50

1.00 Tension shear stregth (MPa) stregth shear Tension

0.50

- Neat PF 50% BPF 50% C-BPF 50% PE- 50% PE-C- BPF BPF

Figure 7-7 Tensile strength of the three plywood samples bonded with the neat PF and BPF resole resins (dry strength: test after conditioning, wet strength: test after boiling in water for 3 h).

Interestingly under dry condition, the tensile shear strength for 50% PE-BPF (2.65 MPa) and 50% PE-C-BPF resoles (2.33 MPa) are even higher than that of the neat PF resole (2.25 MPa), although the dry bonding strength for the 50% BPF (2.02 MPa) and 50% C-BPF (1.48 MPa) are lower than that of the neat PF resole. However, dry bonding strength for all BPF resoles are still comparable to the neat PF resole, and higher than the minimum requirement of dry bonding strength (1.2 MPa)

199 in accordance to the JIS K-6852 Standard. The dry bonding performance of the phenol extracts- based BPF resoles are superior to the starch/tannin/kraft lignin-based PF wood adhesives reported in literature [31,32]. The use of the phenolic extracts as a substitute for phenol in the synthesis of BPF resoles produced high-performance adhesives for plywood bonding, which is believed attributed to the lower molecular weights and enriched phenolic compositions of the phenolic extracts (as shown and discussed previously in Table 7-4 and Fig. 7-3). After being boiled in water for 3 h, all plywood specimens bonded with either a BPF or the neat PF resole showed decreased boning strength, and the wet bonging strength of all BPF resoles are in the range from 1.27 MPa (50% C-BPF) to 1.97 MPa (50% PE-BPF), all above the minimum requirement of wet bonding strength (1.0 MPa) in accordance to the JIS K-6852 Standard.

7.4 Conclusion

In this study, biocrude oils were obtained from HTL of HL with or without the catalysis of hematite ore. A neat PF resole and four BPF resoles were prepared using whole biocrude oils and the phenolic extracts (PE) from the oils to substitute 50% of phenol. The obtained BPF resoles were comprehensively characterized, and the major conclusions can be summarized as follows: (1) All BPFs have similar physical/chemical properties (non-volatile content, pH value, functional structure, etc.) to the neat PF resole. (2) All BPF resoles contain a higher free formaldehyde and less thermally stable than the neat PF resole. (3) The presence of large molecules of phenolic components derived from lignin enables the curing of the BPF resoles at a lower temperature, although the curing speed of the BPF resoles decreases indicated by their slightly higher curing activation energy when compared with the neat PF resole. (4) The dry and wet boning strengths for all BPF resoles meet and exceed the minimum requirements in accordance to the JIS standard. The dry bonding strengths of BPF resoles prepared with the phenolic extracts are higher than that of the BPF resoles prepared with the whole biocrude oils and the neat PF resole. (5) The superior performance of the phenolic extracts from the HTL biocrude oils can be attributed to the lower molecular weights and enriched phenolic compositions of the phenolic extracts.

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7.5 References

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[2] Khan MA, Ashraf SM, Malhotra VP. Eucalyptus bark lignin substituted phenol formaldehyde adhesives: A study on optimization of reaction parameters and characterization. J Appl Polym Sci 2004;92:3514–23. doi:10.1002/app.20374.

[3] Alam Khan M, Marghoob Ashraf S, Prakash Malhotra V. Development and characterization of a wood adhesive using bagasse lignin. Int J Adhes Adhes 2004;24:485–93. doi:10.1016/j.ijadhadh.2004.01.003.

[4] Cheng S, Yuan Z, Leitch M, Anderson M, Xu C. Highly efficient de-polymerization of organosolv lignin using a catalytic hydrothermal process and production of phenolic resins/adhesives with the depolymerized lignin as a substitute for phenol at a high substitution ratio. Ind Crop Prod 2013;44:315–22. doi:10.1016/j.indcrop.2012.10.033.

[5] Moubarik A, Allal A, Pizzi A, Charrier F, Charrier B, Moubarik A, et al. Characterization of a formaldehyde-free cornstarch-tannin wood adhesive for interior plywood Beschreibung eines neuen formaldehydfreien Maisstärke-Tannin Holzklebstoffes für Sperrholz im Innenbereich. Eur J Wood Prod 2010;68:427–33. doi:10.1007/s00107-009-0379-0.

[6] Moubarik A, Charrier · B, Allal A, Charrier F, Pizzi A, Charrier B, et al. Development and optimization of a new formaldehyde-free cornstarch and tannin wood adhesive. Eur J Wood Prod Eur J Wood Prod 2010;68:167–77. doi:10.1007/s00107-009-0357-6.

[7] Vázquez G, González-Lvarez J, López-Suevos F, Antorrena G. Rheology of tannin-added phenol formaldehyde adhesives for plywood n.d. doi:10.1007/s00107-001-0277-6.

[8] Özacar M, Soykan C, Şeng??l İA. Studies on synthesis, characterization, and metal adsorption of mimosa and valonia tannin resins. J Appl Polym Sci 2006;102:786–97. doi:10.1002/app.23944.

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[10] Feng S, Yuan Z, Leitch M, Xu CC. Adhesives formulated from bark bio-crude and phenol formaldehyde resole. Ind Crop Prod 2015;76:258–68. doi:10.1016/j.indcrop.2015.06.056.

[11] Dereca Watkins ଝ, Nuruddin M, Hosur M, Tcherbi-Narteh A, Jeelani S. Extraction and characterization of lignin from different biomass resources 2015. doi:10.1016/j.jmrt.2014.10.009.

[12] Effendi A, Gerhauser H, Bridgwater A V. Production of renewable phenolic resins by thermochemical conversion of biomass: A review ARTICLE IN PRESS. Renew Sustain Energy Rev 2008;12:2092–116. doi:10.1016/j.rser.2007.04.008.

[13] Park HJ, Park KH, Jeon JK, Kim J, Ryoo R, Jeong KE, et al. Production of phenolics and aromatics by pyrolysis of miscanthus. Fuel 2012;97:379–84. doi:10.1016/j.fuel.2012.01.075.

[14] Guo Z, Wang S, Gu Y, Xu G, Li X, Luo Z. Separation characteristics of biomass pyrolysis oil in molecular distillation. Sep Purif Technol 2010;76:52–7. doi:10.1016/j.seppur.2010.09.019.

[15] Yoshikawa T, Shinohara S, Yagi T, Ryumon N, Nakasaka Y, Tago T, et al. Production of phenols from lignin-derived slurry liquid using iron oxide catalyst. Appl Catal B Environ 2014;146:289–97. doi:10.1016/j.apcatb.2013.03.010.

[16] Yoshikawa T, Yagi T, Shinohara S, Fukunaga T, Nakasaka Y, Tago T, et al. Production of phenols from lignin via depolymerization and catalytic cracking. Fuel Process Technol 2013;108:69–75. doi:10.1016/j.fuproc.2012.05.003.

[17] Kleinert M, Barth T. Phenols from lignin. Chem Eng Technol 2008;31:736–45. doi:10.1002/ceat.200800073.

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[18] Fang Z, Sato T, Smith RL, Inomata H, Arai K, Kozinski JA. Reaction chemistry and phase behavior of lignin in high-temperature and supercritical water 2007. doi:10.1016/j.biortech.2007.08.008.

[19] Tejado A, Peñ C, Labidi J, Echeverria JM, Mondragon I. Physico-chemical characterization of lignins from different sources for use in phenol–formaldehyde resin synthesis 2006. doi:10.1016/j.biortech.2006.05.042.

[20] Karagöz S, Bhaskar T, Muto A, Sakata Y. Effect of Rb and Cs carbonates for production of phenols from liquefaction of wood biomass 2004. doi:10.1016/j.fuel.2004.06.023.

[21] Tymchyshyn M, Xu C. Liquefaction of bio-mass in hot-compressed water for the production of phenolic compounds n.d. doi:10.1016/j.biortech.2009.11.091.

[22] Feng S, Yuan Z, Leitch M, Xu CC. Hydrothermal liquefaction of barks into bio-crude - Effects of species and ash content/composition. Fuel 2014;116:214–20. doi:10.1016/j.fuel.2013.07.096.

[23] Cheng S, DCruz I, Wang M, Leitch M, Xu C. Highly efficient liquefaction of woody biomass in hot-compressed alcohol-water co-solvents. Energy and Fuels 2010;24:4659–67. doi:10.1021/ef901218w.

[24] Yao S, Du Y, Huang F, Wang S, Wang M. Co-liquefaction of lignite and biomass over Ni 7 W 3 and Ni 3 W 7 catalysts. Can J Chem Eng 2015;93:1335–42. doi:10.1002/cjce.22220.

[25] Veses A, Puértolas B, Callén M, García T. Catalytic upgrading of biomass derived pyrolysis vapors over metal-loaded ZSM-5 zeolites: Effect of different metal cations on the bio- oil final properties. Microporous Mesoporous Mater 2015;209:189–96. doi:10.1016/j.micromeso.2015.01.012

[26] Del RLF, Wafa ADW, Mao C, Yuan Z, A novel post-treatment to enhance the enzymatic hydrolysis of pretreated lignocellulosic biomass, WO2016138587A1, WO Application, September 9, 2016.

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[27] Zhang W, Ma Y, Wang C, Li S, Zhang M, Chu F. Preparation and properties of lignin– phenol–formaldehyde resins based on different biorefinery residues of agricultural biomass. Ind Crops Prod 2013;43:326–33. doi:10.1016/j.indcrop.2012.07.037.

[28] Hoong YB, Paridah MT, Loh YF, Koh MP, Luqman CA, Zaidon A. Acacia mangium Tannin as Formaldehyde Scavenger for Low Molecular Weight Phenol- Formaldehyde Resin in Bonding Tropical Plywood Acacia mangium Tannin as Formaldehyde Scavenger for Low Molecular Weight Phenol-Formaldehyde Resin in Bonding Tropical Plywood. J Adhes Sci Technol 2010;24:8–10. doi:10.1163/016942410X507740doi.org/10.1163/016942410X507740.

[29] Cheng S, D’Cruz I, Yuan Z, Wang M, Anderson M, Leitch M, et al. Use of biocrude derived from woody biomass to substitute phenol at a high-substitution level for the production of biobased phenolic resol resins. J Appl Polym Sci 2011;121:2743–51. doi:10.1002/app.33742.

[30] O’Connor D, Blum FD. Thermal stability of substituted phenol-formaldehyde resins. J Appl Polym Sci 1987;33:1933–41. doi:10.1002/app.1987.070330606.

[31] Moubarik A, Pizzi A, Allal A, Charrier F, Charrier B. Cornstarch and tannin in phenol– formaldehyde resins for plywood production. Ind Crops Prod 2009;30:188–93. doi:10.1016/j.indcrop.2009.03.005.

[32] Danielson B, Simonson R. Kraft lignin in phenol formaldehyde resin. Part 1. Partial replacement of phenol by kraft lignin in phenol formaldehyde adhesives for plywood Kraft lignin in phenol formaldehyde resin. Part 1. Partial replacement of phenol by kraft lignin in phenol formaldehyde adhesives for plywood Kraft lignin in phenol formaldehyde resin. Part 1. Partial replacement of phenol by kraft lignin in phenol formaldehyde adhesives for plywood. J Adhes Sci Technol 1998;12:923–39. doi:10.1163/156856198X00542doi.org/10.1163/156856198X00542.

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Chapter 8

8 Conclusions and Future Work

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This chapter summarizes the major findings and contributions from studies conducted in this research work. The recommendations for future works pertaining to the improvement of current research are also provided.

8.1 General Conclusions

The aim of this study was to investigate novel techniques for producing monomeric aromatics/phenolics from hydrolysis lignin (HL) for potential applications as fuel, fuel additives and chemicals. Effects of temperatures (400 – 800ᵒC) on fast pyrolysis were studied to examine the relationship between thermal cracking and maximum oil product yield with considering quantity of aromatics/phenolics were produced in the resulted bio-oil. Catalyst screening with different commercial zeolite catalysts for catalytic fast pyrolysis (CFP) of HL was investigated at selected temperature ranges (450, 450, and 500ᵒC) to find a highly selective catalyst to enhance bio-oil production with high monomeric aromatics/phenolics content. Then, ZSM-5 was modified to obtain tailored strengths of acidity and improved resistance to carbon/coke deposition, With the

H2SO4-acidified ZSM-5, the CFP of HL achieved a high yield (151 mg/g-HL) at 450˚C. Moreover, the operating conditions of co-liquefaction of lignin and lignite coal, such as temperature, reaction time were optimized, and different types of iron ore were screened for production of high yields of phenolic biocrude oils. The optimized operating conditions from the co-liquefaction were employed to produce biocrude from HL in water-ethanol (50:50, v/v) mixture with hematite ore as the catalyst. More importantly, the phenolics of the HL-derived biocrude was extracted and the phenolic extracts were used a bio-substitute to phenol for the synthesis of bio-phenol formaldehyde (BPF) resoles as wood adhesives.

The following detailed conclusions could be drawn from this research:

➢ The use of zeolite-X catalyst in fast pyrolysis of lignin shifted the peak temperature where maximum bio-oil yield was produced from 600 ᵒC to 500 ᵒC. The presence of the catalyst reduced bio-oil yield slightly from 60 % to 56 %, accompanied by increased gas yield and char yield, due to catalyzed cracking reactions of the volatile vapor.

206

➢ Catalytic fast pyrolysis of hydrolysis lignin with zeolite-X produced more water in the bio- oils likely due to the hydrodeoxygenation/de-hydration reactions catalyzed by the acidic zeolite-X catalyst. ➢ Zeolite-X remarkably increased the yield of monomeric phenolic compounds in the catalytic fast pyrolysis of hydrolysis lignin at all temperatures (400 - 800 ᵒC). No significant changes in the catalyst properties (crystallinity, acidity, textural structure) during fast pyrolysis of lignin suggesting superb stability of the catalyst in the process. The high activity and stability of the zeolite-X catalyst might be owing to its strong acidity and low pore volume. ➢ The most abundant monomeric phenolics in the lignin-derived bio-oils (irrespective of the presence of catalyst) are guaiacol, syringol, 4-methoxy-3-(methoxymethyl) phenol and metoxyeugenol, at all temperatures, which may be used for production of phenolic resole adhesives or food preservatives. ➢ Zeolite X could effectively catalyze cracking of primary of pyrolysis vapors from lignin to form more monomeric phenolics.

➢ Hematite iron ore (consisting mainly of hematite (Fe2O3) and goethite (FeOOH)), in either reduced or un-reduced form, was found to be extraordinarily active for promoting heavy

oil (HO) yield. At 400 C for 2 h, addition of the H2-reduced hematite ore dramatically enhanced co-liquefaction process and produced heavy oil (HO) at a high yield close to 42 wt.%, almost doubling that of the operation without catalyst.

➢ The results demonstrated a positive synergy effect on HO yield during co-liquefaction of the HL lignin and XL lignite coal.

➢ Co-liquefaction of HL and XL in the presence of catalyst, specially an in-situ reduced

catalyst, produced much lower Mw monomeric aromatic/phenolic compounds. The HOs from the co-liquefaction may be used to substitute phenol for producing bio-based phenolic resins as bonding agents and adhesives.

➢ The use of catalyst produced HO with greatly increased C content, reduced O content and hence increased HHV.

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➢ Existence of a Zeolite catalyst with either high total acidity (Zeolite X) or more Bronsted acid sites (ZSM-5) could promote hydrodeoxygenation reactions on the acidic sites of the catalyst leading to oil products with a greater heating value.

➢ Zeolite Y (CBV-600) and ZSM-5 (CBV-8014) are most effective catalysts for promoting the yield of total monomeric aromatics/phenolics in CFP of HL. The highest yield of monomeric aromatic/phenolic compounds (0.11 g/g of HL) was obtained by CFP of HL with ZSM-5 (CBV-8014) catalyst owing to its more Bronsted acid sites.

➢ During the CFP operations, no significant change in the ZSM-5 catalyst’s crystalline structure, while the catalyst’s total acidity and specific surface area/porosity decreased due to the deposition of heavy organics on the spent Zeolite catalysts. However, all these properties could restore to those of the refresh catalyst, suggesting a good potential of recycling the catalyst in industrial applications.

➢ All ZSM-5 based catalysts contain both Lewis and Bronsted acid sites. ZSM-5 and Ni-

ZSM-5 have weak Lewis acid sites and Bronsted acid sites, and both acid sites, in particular

Bronsted acid sites of two acidified ZSM-5 catalysts (H₂SO₄-ZSM-5, H₃PO₄-ZSM-5) are

remarkably higher than those of the untreated ZSM-5 catalyst.

➢ Irrespective of the use of catalyst, the bio-oil and char yields in all tests remained almost

the same in the narrow ranges of 53-58% and 27-30%, respectively, whereas the presence

of a catalyst consistently produced a higher gas yield.

➢ Among all catalysts, the two acidified catalysts, in particular the H₂SO₄-ZSM-5, produced

bio-oils with best quality, e.g., the highest pH value (5.72), the highest HHV (27.83 MJ/kg),

the highest C content (67.42 %) and the lowest O content (25.18 %) and the smallest O/C

(0.3). H₂SO₄-ZSM-5 has the strongest Bronsted acid sites that could significantly catalyze

the cracking/hydrodeoxygenation/dehydration reactions and hence lead to the best quality

of the oil product.

208

➢ Among all catalysts, the two acidified catalysts, in particular the H₂SO₄-ZSM-5, produced

bio-oils with best quality, e.g., the highest pH value (5.72), the highest HHV (27.83 MJ/kg),

the highest C content (67.42 %) and the lowest O content (25.18 %) and the smallest O/C

(0.3). H₂SO₄-ZSM-5 has the strongest Bronsted acid sites that could significantly catalyze

the cracking/hydrodeoxygenation/dehydration reactions and hence lead to the best quality

of the oil product.

➢ The H2SO4-ZSM-5 demonstrated to be thermally stable and has superb resistance to

carbon/coke deposition, owing to its microporous structure, relative large BET surface area

and presence of strong Bronsted acid sites.

➢ All BPFs have similar physical/chemical properties (non-volatile content, pH value, functional structure, etc.) to the neat PF resole.

➢ All BPF resoles contain a higher free formaldehyde and less thermally stable than the neat PF resole.

➢ The presence of large molecules of phenolic components derived from lignin enables the curing of the BPF resoles at a lower temperature, although the curing speed of the BPF resoles decreases indicated by their slightly higher curing activation energy when compared with the neat PF resole.

➢ The dry and wet boning strengths for all BPF resoles meet and exceed the minimum requirements in accordance to the JIS standard. The dry bonding strengths of BPF resoles prepared with the phenolic extracts are higher than that of the BPF resoles prepared with the whole biocrude oils and the neat PF resole.

➢ The superior performance of the phenolic extracts from the HTL biocrude oils can be attributed to the lower molecular weights and enriched phenolic compositions of the phenolic extracts.

209

8.2 Contributions and Novelty

Based on the results from this research, the main contributions and novelties of the thesis are summarized as follows:

➢ Discovering zeolite-X as a novel catalyst for catalytic cracking process toward highest aromatics/phenolics production via catalytic fast pyrolysis of hydrolysis lignin

➢ Screening of different zeolite catalysts on products quality and yield of aromatics/phenolics in catalytic fast pyrolysis of hydrolysis lignin

➢ Modifying of ZSM-5 catalyst to obtain tailored strengths of acidity and improved resistance to carbon/coke deposition for catalytic fast pyrolysis of hydrolysis lignin

➢ Optimizing reaction conditions for both liquefaction and co-liquefaction of lignin and lignite for aromatics/phenolics production

➢ Extracting phenolics from biocrude oils and substituting phenol for synthesis of bio-phenol formaldehyde resins/adhesives

8.3 Recommendations for Future Work

This study has achieved novel catalysts for catalytic fast pyrolysis or hydrothermal liquefaction of lignin or lignocellulosic biomass for production of monomeric aromatic/phenolic compounds for potential applications as fuels, fuel additives or chemicals. The experiments were conducted in a bench-scale fixed bed reactor or autoclave reactor. For real applications and up-scaling of this research, following work is required:

1. A scale-up process using fluidized bed reactor can be tested.

2. More work should be done in the application of the bio-phenol formaldehyde resins, aiming to improve the phenol substitution ratio to >50% and enhance the water resistance of the bio-resins, as well to find approaches to deceasing the free formaldehyde in the bio oil- based resins.

210

3. Other types of lignin, e.g., kraft lignin – a more abundant waste stream from pulp/paper mills, should be investigated as resources for the production monomeric aromatics/phenolics.

4. Other organic solvents than the ethanol-water mixture, may be explored to obtain effective liquefaction of lignin for phenolic biocrude production.

5. Combination of acidified and metal loaded catalyst on catalytic fast pyrolysis should be tested.

6. Techno-economic analysis of a large-scale process of CFP or HTL of lignin may be conducted to demonstrate the economical promise of the technologies for future commercialization.

7. Cost-effective approaches should be explored for extraction of aromatics/phenolics from bio-oils.

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Appendices

Appendix A: Production of bio-oil and aromatics by catalytic fast pyrolysis of woody biomass

In this section, we present some of our own research findings that contribute as evidence to this work. Catalytic and non-catalytic pyrolysis of pine sawdust for the conversion to monomer aromatic compounds investigated. While CFP of lignin includes hydrotreatment and catalytic vapor cracking [1], the latter is preferred by several researchers, since it is applicable below mild conditions (400 – 600ᵒC and atmospheric pressure) and also at low cost. A range of catalysts, including microporous i.e. HZSM-5, Zeolite-X, Ru-Zeolite-X and blank test have been used and their selectivity towards monomer aromatic hydrocarbons was characterized. Various conditions (flow rate of sweeping gas, temperature, catalyst) have a different effect on bio-oil and aromatic yields.

1.1 Materials

Eastern white pine (Pinus strobes L.) sawdust used in this study was obtained from a local sawmill in Thunder Bay Ontario. It was sieved to obtain particles smaller than 2 mm and dried at 105 °C for 2 h. Compositions (cellulose, hemicellulose and lignin) and proximate and ultimate analyses of pine sawdust sample are listed in Table 1. The ash, fixed carbon, and volatile matter contents of the pine sawdust sample were determined by thermogravimetric analysis (TGA) in N2 at 10°C/min to 800°C. Elemental composition of the dry sawdust sample was analyzed on an elemental analyzer (CHNS-O Analyzer FLASHEA 1112 SERIES, Thermo Scientific). The biomass composition analysis was performed on the extractive-free sample pre-extracted with acetone. Cellulose and hemicellulose were determined according to TAPPI test method T249 cm- 85, and the acid-soluble and acid-insoluble lignin were determined according to the TAPPI test method T222 om-88.

The catalyst supports used in this study were Zeolite-X (SiO2/Al2O3 = 5), purchased from Sigma-

Aldrich, and HZSM-5 (SiO2/Al2O3 = 38) purchased from a company in China. Ru precursor ruthenium nitrosylnitrate was obtained from Sigma-Aldrich.

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Table 1. Analyses of the pine sawdust used in this study

Description Content (wt.%)

Biomass composition (dry and extractive-free basis)

Cellulose 40.2

Hemicellulose 21.9

Lignin 28.4

Ultimate (dry and ash-free basis)

Carbon 48.9

Hydrogen 6.1

Oxygen 43.6

Nitrogen 1.4

Sulfur 0

Proximate analysis (dry basis)

Volatiles 87.2

Fixed carbon 11.7

Ash 1.1

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1.1.1 Catalyst preparation

Ru-Zeolite-X supported catalyst (5 wt% Ru with respect to the weight of the support) was prepared by wet impregnation method. In a typical run, 0.5g ruthenium nitrosylnitrate was dissolved in 10 mL distilled water and 3 g Zeolite-X support was added under magnetic stirring for 3h. The excess water was removed by oven drying at 105 °C for 12 h. The supported Ru catalyst was calcined in air at 300 ° for 3h, and it was reduced in H2 flow @ 40 ml/min at 300 °C for 3h prior to the use.

1.1.2 Catalyst characterization

Textural properties of the fresh/used catalysts were measured by N2 isothermal adsorption at 77 K (NOVA 1200e surface area and pore size distribution analyzer), and the results for the fresh catalysts are presented in Table 2. The surface area was calculated by using Brunauer-Emmett-

Teller (BET) method. Total pore volume was estimated using the volume of N2 gas adsorbed at a relative pressure (P/P0) of 0.99. Density functional theory (DFT) was used to characterize the pore size distribution based on N2 desorption isotherm. The fresh/used catalysts will also characterized by TGA for coke formation and by XRD for the crystalline structure of the loaded metal (s) and the support.

Table 2. Textural properties of the fresh catalysts

BET Total pore Average pore size Catalyst surface volume (cc/g) (nm) area (m2/g)

Zeolite-X 900 2.610 45

Ru-Zeolite-X 11 0.053 1

HZSM-5 350 0.126 2

214

1.2 Experimental apparatus

Fast pyrolysis experiments were carried out in a drop-tube/fixed-bed reactor (Figure 1) made of a SS 316L tube (¾” O.D., 26.5” length). The reactor was heated in an electric furnace whose temperature was controlled by a temperature controller. The furnace temperature could be varied from 300 to 1200 °C. The nitrogen flow rates through the biomass feeder and reactor was set and controlled with a Bronkhorst High-Tech mass flow controller meter (EL-FLOW), and it can be set from 50 to 200 ml/min.

1.3 Experimental procedure

In a typical run, fast pyrolysis of white pine sawdust was carried out with or without catalyst at

500 °C with sweeping N2 gas at a flow rate of 97 ml/min. 3 g of bone-dried sample feedstock was loaded into the feeder (1” OD tube) above the reactor separated from the reactor by a ball valve, and 0.2g of quartz wool was put in the bottom of the reactor as the catalyst-bed holder on top of which 0.5 g of catalyst (for catalytic experiments) was loaded in the tubular reactor positioned in the hot-zone of the furnace, as illustrated in Figure 2. Leak proof was ensured with high pressure nitrogen gas. Before start the reaction the reactor and the feeder were vacuumed/purged thrice repeatedly to eliminate air inside the reactor system. The reactor was then heated up to 500 °C at a heating rate 10-20°C/min in 97 ml/min N2, and after the reactor temperature reached 500 °C, the biomass in the feeder was fed into the reactor rapidly from opening the ball valve by gentle tapping.

Assuming negligible change in total gas flow rate (97 ml/min N2) during the pyrolysis experiments, the residence time of the vapor inside the 0.5 g catalyst bed (0.7-0.9 mL, depending on the catalyst employed) was estimated to be ~0.5 s. The vapor product was condensed into a liquid product in a condenser refrigerated at -10°C. The non-condensable gaseous products were collected using a gas bag for 20 min reaction, and the total mass of the gas collected (mainly N2) was measured by accurately weighing, from which the total volume of the gas was approximately calculated assuming ideal gas law for N2. After being cooled to room temperature, the reactor was washed with 150 ml of acetone for recovery of liquid product (bio-oil).

215

2 Characterization of bio-oil

Elemental analysis of feedstock (pine sawdust) and bio-oils and chars were analyzed by an elemental analyzer (CHNS-O Analyzer FLASHEA 1112 SERIES, Thermo Scientific). The heating value was calculated based on Dulong’s formula. The water content of bio-oil was determined by Karl-Fisher titration method using a Mettler Toledo DL32 colorimetric titrator. The viscosity and pH values of bio-oil were measured by viscosity meter (CAP 2000+ Viscometer, Brookfield) and pH meter (ORION 2STAR PH Benchtop, Thermo Scientific), respectively.

The bio-oil products were qualitatively analyzed with a gas chromatograph-mass spectrometer [GC-MS, Agilent Technologies, 5977A MSD) with a SHRXI -5MS column (30 m × 250 m × 0.25 m) and a temperature program of 60oC (hold for 2 min) → 120 oC (10 oC/min) → 280 oC (8 oC /min, hold for 5 min)]. Compounds in the oil were identified by means of the NIST Library with 2011 Update. Molecular weight distributions of the bio-oils were measured by Waters Breeze GPC-HPLC instrument equipped UV detector using styragel HR1 as the analytical column at 40 °C using 1 mL min-1 THF as the mobile phase. Polystyrene narrow standards were used for calibration of the GPC-UV. The vol.% compositions of gaseous products were determined using GC-TCD (Agilent Micro-GC 3000). The mass of produced gas is calculated based on the total volume of the gas and vol% of each gaseous component from GC-TCD analysis, assuming ideal gas law. The char/coke yield was estimated from TGA of the mixture of used catalyst and char from the test employing a PerkinElmer Pyris 1 TGA in 20 mL/min air heated from 40 oC to 800 oC at 10 oC /min.

216

(a) (b)

Figure.1 Schematic diagram (a) and photo (b) of the reactor system used for catalytic fast pyrolysis of biomass

3 Effects of the sweeping gas flow rate, pyrolysis temperature, and catalysts on product yields

The role of sweeping gas during FP and CFP is to carry the pyrolysis vapors out of the reactor and manipulate the vapor residence time inside the reactor, which would affect the product yields. As is well known, changing the sweeping gas flow rate would directly alter the vapor residence time. Figure 2 shows the yields of products (Bio-oil, Char, and Gas) in the FP tests without catalyst at 500 C at the sweeping nitrogen flow rate of 97 ml/min and 58 ml/min, respectively. As shown in the Figure, a higher sweeping flow rate, or a shorter vapor residence time, is favorable for

217 increasing the yield of bio-oil, while reducing the production of Char and Gas products. This result was expected because shorter residence time for the vapor inside the hot zone of the reactor can minimize secondary reactions such as thermal cracking, re-polymerization, and re-condensation, and hence maximize the liquid product yield, and reduce the formation of char and gas products [2].

Gas yield Char yield Bio-oil yield 100%

90%

80%

70%

60%

50% Yield 40%

30%

20%

10%

0% A B

Figure 2. Yields of the products (500 C without catalyst) at two sweeping N2 flow rates: (A) 97 ml/min, and (B) 58 ml/min.

It is well known that the main parameter among the operating conditions is the pyrolysis temperature. In Figure 3 we show the effects of pyrolysis temperature of pine sawdust on product distribution for FP at a sweeping nitrogen flow rate of 97 ml/min. Three pyrolysis temperatures (400, 500 and 600C) were tested. Increasing the pyrolysis temperature from 400 to 600 °C continuously decreased the yield of char accompanied by a monotonic increase in gas yield, but the bio-oil yield was observed to reach a maximum at 500 °C. A further increase in pyrolysis temperature decreased the bio-oil yield due to the promoted C-C bond cleavage reactions at higher

218 reaction temperatures, converting the pyrolysis vapor into gaseous products and hence reducing the bio-oil yield, as similarly reported in the literature [3].

Bio-oil yield Gas yield Char yield 70%

60%

50%

40%

Yield 30%

20%

10%

0% 350 450 550 650 Temperature (C)

Figure 3. Effects of pyrolysis temperature on product distribution (sweeping nitrogen flow rate of 97 ml/min, without catalyst).

The most effective catalyst for conversion of lignin to aromatics that has been used in fixed bed and fluidized bed reactors is the zeolite catalyst (as previously shown in Table 2-3). Figure 4 represents bio-oil yields with different catalysts from CFP of pine sawdust at 500 C at a sweeping nitrogen flow rate of 97 ml/min. The non-catalytic pyrolysis had the highest bio-oil yield, approx. 66 wt.%. The CFP tests with a zeolite-based catalyst (Zeolite-X, Ru-Zeolite-X or HZSM-5) resulted in a decrease in liquid oil yield and an increase in gas yield. With the Zeolite-X based catalysts, a higher amount of solid products was generated (char and coke), likely due to the stronger acidity of the zeolite promoting cracking and re-polymerization reactions to form more coke on the surface of the catalysts [4,5]. Among the studied catalysts, HZSM-5 performed the best, resulting in a much higher bio-oil yield, and significantly lower coke yield than the other two

219

Zeolite-X based catalysts. In fact, many literature studies have also demonstrated that HZSM-5 performs better than other zeolites and solid acid catalysts in CFP of biomass for high-quality bio- oil production [5].

Gas yield Solid yield Bio-oil yield

100%

90%

80%

70%

60%

50% Yield 40%

30%

20%

10%

0% No-Catalyst Zeolite-X Ru-Zeolite-X HZSM-5

Figure 4. Bio-oil yields with different catalysts (at 500 C and sweeping nitrogen flow rate of 97 ml/min).

Table 3 shows the effects of catalysts on gas product distribution from the CFP of pine sawdust at 500 C and sweeping nitrogen flow rate of 97 ml/min. Generally, the use of an acidic catalyst resulted in an increase in the amount of H2, CO, CO2, and CH4 and C2-C3 hydrocarbon species, as expected due to the promoted cracking of the pyrolytic vapor over the acidic sites of the catalyst, as evidenced by the much greater yield of Gas products (Figure 9). The formation of CO and CO2 could be attributed to deoxygenation reactions of the vapor, on which the HZSM-5 catalyst showed the best activity. Although the total yield of C1-C3 HCs gases was slightly increased with both

220

Zeolite-X and HZSM-5 catalysts, suggesting increased C-C cracking reactions, the C1-C3 HCs gases yield was found to be much lower with the Ru-Zeolite-X catalyst, accompanied by markedly increased H2, suggesting that the Ru-loaded zeolite might catalyze the steam reforming reaction of

HCs (CH4 + 2H2O → 4H2 + CO2).

Table 3. Effects of catalyst on gas product distribution (at 500 C and sweeping nitrogen flow rate of 97 ml/min).

Catalyst None Zeolite-X Ru-Zeolite-X HZSM-5

H2 0.1±0.0 4.6±1.0 8.3±0.4 3.6±0.9

CO 23.7±5.5 22.6±1.3 4.5±0.8 Gas yield (vol.%)

CO2 21.7±2.4 10.8±1.6 10.8±0.7 37.3±5.7

CH4 and C2-C3 9.6±0.3 3.3±0.5 2.9±0.8 1.0±0.4

Bio-oil products include both aqueous and oily phases. The aqueous phase is composed of sugars, alcohols, carboxylic acids and mainly water derived from the moisture content of the feedstock and from pyrolytic reactions. The oil phase is rich in organic compounds whose composition varies significantly, depending on the feedstock composition and the operating conditions (temperature, vapor residence time and catalyst). The effects of various catalysts on the bio-oil quality were investigated by GPC analysis for the molecular weights and distribution of the bio-oil products (Figure 5), elemental analysis (Table 4) and GC-MS analysis (Figure 6 and Table 5) for the chemical composition of the oils.

Figure 5 presents GPC chromatograms of the bio-oils derived from fast pyrolysis of pine sawdust with and without a catalyst. As clearly shown in Figure 5, the GPC chromatogram of the bio-oil obtained with a catalyst (in particular Ru-Zeolite-X and HZSM-5) shifts right to a longer elution time (i.e., lower molecular weights) compared with that without a catalyst. This result suggests

221 that the presence of a zeolite-based catalyst in the fast pyrolysis of biomass, though it decreased the bio-oil yield, improved the quality of the oil products with reduced molecular weights. The number-average and weight-average molecular weight, Mn and Mw, respectively, are provided in Table 5, from which the Mw of all bio-oils decreases in the following order: 430 g/mol (no catalyst) > 338 g/mol (Zeolite-X) > 262 g/mol (HZSM-5) > 255 g/mol (Ru-Zeolite-X).

HZSM-5 No Catalyst Zeolite-X

Ru-Zeolite-X UV Absorbance UV

0 5 10 15 20

Elution time(min)

Figure 5. GPC chromatograms of the bio-oils derived from fast pyrolysis of pine sawdust with and without catalyst (at 500C and sweeping nitrogen flow rate of 97 ml/min).

The physical and chemical properties of the bio-oils derived from fast pyrolysis of pine sawdust with and without catalyst are comparatively listed in Table 5. As clearly shown in the Table, the presence of a catalyst in the catalytic fast pyrolysis of biomass produced bio-oils with significantly improved qualities, e.g., smaller viscosity (9.8 mPa.s without catalyst vs. 2.3-8.3 mPa.s with a catalyst), reduced water content (~48 wt% vs. 23-38 wt%), increased heating value (HHV, 11 MJ/kg vs. 14-21 MJ/kg), higher C content (36 wt% vs. 43-50 wt%), lower O content (57 wt% vs. 41-50 wt%) and decreased O/C molar ratio (1.2 vs. 0.6-0.9). Among the three presented catalysts, HZSM-5 and Ru-Zeolite-X performed much better than Zeolite-X in terms of bio-oil product quality enhancement (Mw, viscosity, water content, HHV, C content, O content, O/C molar ratio, etc.).

222

Figure 6 illustrates GC-MS total ion chromatograms of bio-oils obtained without and with various catalysts, from which the chemical compositions of various bio-oils are qualitatively analyzed and summarized in Table 5. All bio-oils obtained are a complex mixture of highly oxygenated organics such as phenols, ethers, aldehydes, ketones, carboxylic acids, and hydrocarbons, originating from the degradation of cellulose, hemicellulose, and lignin in the pine sawdust. As shown in Table 5, the non-catalytic pyrolysis of pine sawdust produced bio-oil mainly containing phenols, ethers, carboxylic acids, ketones, and aldehydes. Interestingly, the catalytic pyrolysis of the biomass, in particular with the Ru-Zeolite-X and HZSM-5 catalysts, produced bio-oils with significantly decreased ether compounds and increased mono-phenols, such as phenol, 2-methyl-phenol, 2,4- dimethylphenol, and catechol, likely due to the selective catalytic cleavage of C-O-C bonds. Besides, Ru- Zeolite-X catalyst showed higher catalytic performance compared to HZSM-5 by decreasing the molecular weight distribution of bio-oil and producing more aromatic chemicals via selective cleavage of C-O-C bonds. Moreover, these catalysts would facilitate a secondary degradation reaction which helps to decrease the ketone functional group compounds in bio-oil.

223

Table 4. Physical and chemical properties of the bio-oils (at 500 C and sweeping nitrogen flow rate of 97 ml/min).

Elemental composition, Water HHVb Viscosity pH Mn Mw O/C H/C Catalyst (wt %, d.b.) content (MJ/kg) (cP) (-) (g/mol) (g/mol) (-) (-) (wt.%) C H N Oa

1.1 2.1 Blank 35.71 6.43 0.97 56.90 11.11 9.8 46.71 3.11 263 403 9 6

0.8 1.6 Zeolite-X 43.17 6.00 0.94 49.88 14.27 8.3 26.99 2.97 213 338 7 8

0.6 1.9 Ru-Zeolite-X 49.57 7.81 1.55 41.07 20.58 3.7 37.94 2.79 177 255 2 2

0.7 1.9 HZSM-5 44.59 7.06 1.35 47.00 16.77 2.3 23.25 2.93 183 262 9 2

aBy difference and assuming that the sulfur content is negligible;

bDulong formula HHV (MJ/ kg) = 0.3383C + 1.422 (H-O/8)

224

No catalyst 20

x 10000 x 15

5 Abundance

0 0 5 10 15 20 Time (min)

Zeolite-X 8

6 x 100000 x 4

Abundance 2 0 0 5 10 15 20 Time (min)

Ru-Zeolite-X

5 Abundance 0 0 5 10 15 20 Time (min)

225

HZSM-5 20

15 x 100000 x 10

5 Abundance 0 0 5 10 15 20 Time (min)

Figure 6. GC-MS total ion chromatograms of bio-oils obtained without and with various catalysts (at 500C and sweeping nitrogen flow rate of 97 ml/min).

226

Table 5. Compounds identified by GC-MS in different bio-oils (at 500 C and sweeping nitrogen flow rate of 97 ml/min).

Retention MW Group Time Chemical name Formula (g/mol) Blank Zeolite-X Ru-Zeolite-X HZSM-5

3.9 Phenol C6H6O 94 +

6.2 Phenol, 2-methyl- C7H8O 108 + +

6.5 Guaiacol C7H8O2 124 + + + +

Phenol, 2,4- + + 6.9 dimethyl- C8H10O 122

7.1 Catechol C6H6O2 110 + Phenols

7.3 Creosol C8H10O2 136 + + + +

7.8 4-ethylguaiacol C10H12O2 164 + + + +

8.2 4-propylguaiacol C10H14O2 166 +

2-Methoxy-4- + + + + 8.3 vinylphenol C9H10O2 150

8.4 Eugenol C10H12O2 164 + + + +

227

9.2 Vanillin C8H8O3 152 + + + +

9.7 Apocynin C9H10O3 166 + + + +

Naphthalene, 2- + 8.7 methyl- C11H10 142

Hydrocarbon Naphthalene, 2,6- + s 9.5 dimethyl- C12H12 156

Benzo[b]thiophen + 10.3 e, 7-ethyl- C10H10S 162

13.7 Levoglucosan C6H10O5 162 + + +

Benzene, 1,3-

dimethoxy-5- + + [(1E)-2- Ethers 17.3 phenylethenyl]- C16H16O2 240

4H-1-

Benzopyran-4- +

10.7 one, 5-hydroxy-7- C16H12O4 268

228

methoxy-2- phenyl-

Homovanillic + Carboxylic 12.4 acid C9H10O4 182 acids

6.0 Oleic Acid C18H34O2 282 +

1,2-

Cyclopentanedion + + +

11.4 e, 3-methyl- C6H8O2 112

Ketones 2-Propen-1-one, 1-(2,6-dihydroxy-

4- + + methoxyphenyl)-

15.4 3-phenyl-, (E)- C16H14O4 270

9.9 D-Allose C6H12O6 180 +

Aldehydes 2-Propenal, 3-(4- hydroxy-3- + + +

15.3 methoxyphenyl)- C10H10O3 178

229

References

[1] H.J. Park, K.H. Park, J.K. Jeon, J. Kim, R. Ryoo, K.E. Jeong, S.H. Park, Y.K. Park, Production of phenolics and aromatics by pyrolysis of miscanthus, Fuel. 97 (2012) 379–384. doi:10.1016/j.fuel.2012.01.075.

[2] E. Salehi, J. Abedi, T. Harding, Bio-oil from sawdust: Effect of operating parameters on the yield and quality of pyrolysis products, Energy and Fuels. 25 (2011) 4145–4154. doi:10.1021/ef200688y.

[3] E. Salehi, J. Abedi, T. Harding, Bio-oil from sawdust: Pyrolysis of sawdust in a fixed-bed system, Energy and Fuels. 23 (2009) 3767–3772. doi:10.1021/ef900112b.

[4] O.D. Mante, F. a. Agblevor, R. McClung, Fluid catalytic cracking of biomass pyrolysis vapors, Biomass Convers. Biorefinery. 1 (2011) 189–201. doi:10.1007/s13399-011-0019-x.

[5] H.J. Park, J.K. Jeon, D.J. Suh, Y.W. Suh, H.S. Heo, Y.K. Park, Catalytic Vapor Cracking for Improvement of Bio-Oil Quality, Catal. Surv. from Asia. 15 (2011) 161–180. doi:10.1007/s10563-011-9119-7.

230

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257

Appendix C: Curriculum Vitae

Hooman Paysepar

EDUCATION

University of Western Ontario, London, Ontario, Canada Chemical engineering Sep. 2014 – April 2018, Ph.D.

University of Tehran (Azad), Tehran, Iran Chemical Engineering Sep 2005 – Mar 2008

University of Tehran (Azad), Tehran, Iran Chemical engineering Sep 1997 –Jun 2002

HONORS and AWARDS

Mitacs Globalink Research Award for research on "Co‐ liquefaction of lignin and lignite for aromatic fuels and chemicals" in 2016.

RESEARCH and WORK EXPERIENCE

M.Sc's Thesis: A study on decomposition point of hydrocarbon in distillation tower and determine Material factor, the basic factor for predicting the Fire and Explosion Index. (Hazardous control). (2007-8) Supervisors: Prof. Mehrdad Manteghian, Tarbiyat Modares University, Tehran,Iran Dr. Alireza Jirsaraei,Tehran (Azad) University.

B.Sc's Thesis: Cathodic protection design in gas pipelines. (2001-2) Supervisor: Dr. Alireza Jirsaraei, Tehran (Azad) University.

Volunteer: Train 180 Hr , Paksan co. – Manufacturing of detergent powder and quality control , Tehran, Iran. (2002)

258

TEACHING EXPERIENCE

Teaching Assistant University of Western Ontario (Green Process Engineering). (Winter 2018) Teaching Assistant University of Western Ontario (Green Process Engineering). (Fall 2017) Teaching Assistant University of Western Ontario (Staged operations). (Winter 2017) Teaching Assistant University of Western Ontario (Heat Transfer). (Fall 2016) Teaching Assistant University of Western Ontario (Heat Transfer). (Fall 2015) Teaching Assistant University of Western Ontario (Mass Transfer). (winter 2015) Instructor at Boein-zahra University (Fall 2010-2013). Lecturer at Tehran (Azad) University, North Tehran Branch. (spring 2006)

Courses: Unit operations Heat Transfer Fluid mechanics Mathematic in chemical engineering Laboratory

Programming Language: MATLAB