The Selective Epoxidation of Allyl Alcohol to Glycidol

Home , Glycidol

THE SELECTIVE EPOXIDATION OF ALLYL ALCOHOL TO GLYCIDOL

A THESIS SUBMITTED FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

Luke Martin Harvey

B. Eng. (Newcastle), B. Sci. (Newcastle)

Department of Chemical Engineering

The University of Newcastle, Australia

November 2020

This research was supported by an Australian Government Research Training Program (RTP)

Scholarship

STATEMENT OF ORIGINALITY

I hereby certify that the work embodied in the thesis is my own work, conducted under normal supervision. The thesis contains no material which has been accepted, or is being examined, for the award of any other degree or diploma in any university or other tertiary institution and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made. I give consent to the final version of my thesis being made available worldwide when deposited in the University’s Digital Repository, subject to the provisions of the

Luke Harvey

25 November 2020

I ACKNOWLEDGMENT OF AUTHORSHIP

I hereby certify that the work embodied in this thesis contains published paper/s/scholarly work of which I am a joint author. I have included as part of the thesis a written declaration endorsed in writing by my supervisor, attesting to my contribution to the joint publication/s/scholarly work.

By signing below I confirm that Luke Martin Harvey contributed the design of the experimental program, conducted experiments, data analysis and scientific writing to the paper/ publication entitled “Influence of impurities on the epoxidation of allyl alcohol to glycidol with hydrogen peroxide over titanium silicate TS-1” and contributed the epoxidation chemistry portion of the experimentation and scientific writing to the paper/ publication entitled

“Enhancing allyl alcohol selectivity in the catalytic conversion of glycerol; influence of product distribution on the subsequent epoxidation step”.

Prof. Michael Stockenhuber

25 November 2020

II Acknowledgements

I would like to offer my gratitude to my supervisors, Professor Michael

Stockenhuber and Professor Eric Kennedy for their consistent support and encouragement. I can safely say that the next generation of young researchers are off to the best possible start to their careers with mentors of this calibre.

I would like to acknowledge the University of Newcastle, the Australian

Government Research Training Program and African Explosives Ltd. for the financial assistance in maintaining this work.

Thank you to the technical staff in the Faculty of Engineering and Built

Environment at the University of Newcastle. In particular, Scott Molloy, for his continued friendship, guidance and assistance without which we would be utterly lost. Jane Hamson and Justin Houghton for their assistance with laboratory administration, undergraduate teaching and running a tight ship.

Glenn Bryant for his holistic expertise and assistance, particularly in the design and construction of XAS instrumentation.

I truly appreciate my fellow post-graduate colleagues, Penghui, Vincent,

Jim, for their contributions to developing the group and in particular Dr.

Matthew Drewery for keeping the lab running smoothly and being a great friend who I can always bounce ideas off of.

Thank you to my parents, Belinda and Mark, for always being there with love and encouragement when it is most needed and my brother, Mitch, for sharing a laugh when you have the time.

III

Abstract

With the predicted global increase in biodiesel production, it is anticipated that a market oversupply of glycerol, the major by-product

(approximately 10 wt%) of biodiesel manufacture, will occur. It is thus desirable to produce value-added species from waste glycerol. One commercially attractive product is glycidol (2,3-epoxy-1-propanol), a stabiliser used in the manufacture of vinyl polymers, oil additive and a precursor to novel energetic polymeric compounds. In principle, glycerol may be dehydrated to glycidol, however the more commonly used route is through acrolein (acrylaldehyde).

This work examines first enhancing the production of allyl alcohol from glycerol using alkali metal-modified iron oxide catalysts supported on alumina.

In this case, a feed of 35 wt% glycerol was supplied to a plug flow reactor at

340°C under N2 carrier gas. It was found that the product distribution varies according to the acid-base characteristics of the catalyst, modified by the alkali metal. The rubidium-modified iron oxide catalyst was found to provide the best allyl alcohol total yield, where the potassium-modified catalyst provided the highest selectivity to allyl alcohol. The effect of the product distribution on the success of the allyl alcohol epoxidation reaction was then examined. It was found that acrolein in particular is detrimental to the epoxidation reaction, decreasing the allyl alcohol conversion from ca. 50% to 21%. It also has the effect of decreasing the reaction kinetics to 0.14 times the control rate.

This research then focuses on using operando FTIR to determine the mechanism of catalyst inhibition. Instead, a previously unreported oxidation of the vinyl group in allyl alcohol to carbonyl. This reaction was not found to occur

VI over the Ti-free equivalent material, silicalite-1, hence a titanium species was suggested to be the catalytic site for this transformation.

Last, the operando XAFS experiments undertaken in order to determine the structure of the Ti species facilitating the vinyl oxidation reaction is discussed. Using direct interpretation of the post-edge XANES spectra, pre- edge, and theoretical fitting of the EXAFS, it was found that the most likely mechanism is framework titanium with coordinated (-OO-) and H2O groups being dehydrated to a 6-coordinate (HO)2-Ti-(OSi)4 upon re-heating the catalyst wafer. We propose that this is framework titanium with a coordinated

-OH ligand which is responsible for the newly-reported vinyl oxidation mechanism.

List of Publications

Peer-Reviewed Journal Articles

Harvey, L.; Kennedy, E.; Dlugogorski, B. Z.; Stockenhuber, M.;

“Influence of impurities on the epoxidation of allyl alcohol to glycidol with hydrogen peroxide over titanium silicate TS-1”; Applied Catalysis A: General

2015, 489, 241.

Harvey, L.; Sánchez, G.; Kennedy, E. M.; Stockenhuber, M.;

“Enhancing allyl alcohol selectivity in the catalytic conversion of glycerol; influence of product distribution on the subsequent epoxidation step”; Asia-

Pacific Journal of Chemical Engineering 2015, 10, 598.

Harvey, L.; Kennedy, E.; Stockenhuber, M.; “In-Situ XAFS study of an alternative reaction pathway in the TS-1 titanium-peroxo system” (under review).

Conference Papers

Harvey, L.; Kennedy, E.; Stockenhuber, M.; “The Oxidation of Olefins

Over TS-1 Using Hydrogen Peroxide: An Operando FTIR/XAFS Study”

International Conference on Environmental Catalysis; United Kingdom, 2020

Harvey, L.; Kennedy, E.; Stockenhuber, M.; “Operando ftir study on the oxidation of functionalised olefins over TS-1 using hydrogen peroxide”; 19th

International Zeolite Conference (IZC’19); Australia, 2019

Harvey, L.; Kennedy, E.; Stockenhuber, M.; “The Effect of Extraneous

Chemical Impurities on the Epoxidation of Functionalised Olefins”; 8th World

Congress on Oxidation Catalysis; Poland, 2017

Harvey, L.; Kennedy, E.; Stockenhuber, M.; “Evidence for the Presence of a Stable Peroxo Species Formed on Titanium Silicalite”; 9th International

Conference on Environmental Catalysis (9th ICEC), Australia, 2016

Harvey, L.; Kennedy, E.; Stockenhuber, M.; “Selective Epoxidation of

Allyl Alcohol to Glycidol over TS-1: The effect of Solvent and Organic

Impurities”; The Seventh Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT7), Japan, 2014

VII

Table of Contents

Chapter 1. Introduction ...... 1

1.1 Background ………………………………………………………………..2

1.1.1 Fossil Fuels and Their Use ...... 2 1.1.2 Biodiesel Production and the Glycerol ‘Glut’ ...... 3 1.1.3 The Biodiesel Manufacture Process ...... 6 1.2 Pathways to Value-Added Products…………………………………….7

1.2.1 Uses and Reactions of Glycidol ...... 8 1.2.2 Allyl alcohol production from glycerol ...... 13 1.3 References ………………………………………………………………17

Chapter 2. Literature Review on the Catalytic Epoxidation of

Unsaturated Hydrocarbons ...... 19

2.1 Catalysis………………………………………………………………….20

2.1.1 Catalyst Energetics ...... 22 2.1.2 Selectivity of Catalysts ...... 25 2.1.3 Catalytic Mechanisms ...... 27 2.1.4 Langmuir-Hinshelwood ...... 27 2.1.5 Eley-Rideal Model ...... 28 2.1.6 Mars van Krevelen (MvK) Model ...... 29 2.1.7 Autocatalysis ...... 29 2.2 The Chemistry of Epoxides……………………………………………..31

2.3 Allyl Chemistry……………………………………………………………31

2.4 Epoxidation Chemistry…………………………………………………..33

2.4.1 General Methods of Epoxidation ...... 33 2.5 Catalyst Development…………………………………………………...38

2.5.1 Transition metal oxides as epoxidation catalysts ...... 38 2.6 Scope of This Work………………………………………………………42

2.7 References ………………………………………………………………44

Chapter 3. Experimental Methodology and Materials ...... 47

3.1 Experimental Methodology and Preparation of Materials……………48

3.2 Hydrothermal Synthesis of Zeolites…………………………………….48

3.3 Epoxidation Experiments………………………………………………..49

3.4 Fourier Transform Infrared Spectroscopy…………………………….51

3.5 X-Ray Absorption Experiments………………………………………..55

1.1 The Beamline……………………………………………………………58

3.6 References………………………………………………………………60

Chapter 4. Enhancing Selectivity to Allyl alcohol in Glycerol

Conversion ...... 61

4.1 Introduction ………………………………………………………………62

4.2 Experimental……………………………………………………………..65

4.2.1 Materials...... 65 4.2.2 Methodology ...... 65 4.3 Results and Discussion………………………………………………….67

4.3.1 Product distribution in the glycerol DOHD reaction through modification of catalysts with alkali metals ...... 67 4.3.2 The use of glycerol DODH products in the production of glycidol .... 71 4.4 Conclusions ………………………………………………………………74

4.5 References……………………………………………………………….75

Chapter 5. The Effect of Additives on the Rate of Epoxidation of

Allyl Alcohol ...... 77

5.1 Introduction ………………………………………………………………78

5.1.1 The Epoxidation Reaction ...... 80 5.2 Experimental……………………………………………………………..86

5.2.1 Synthesis of Titanium Silicalite-1 (TS-1) ...... 86 5.2.2 Epoxidation Reaction ...... 87 5.3 Results and Discussion………………………………………………….89

5.3.1 Titanium Silicalite-1 Synthesis ...... 89 5.3.2 Epoxidation Reaction ...... 91 5.4 Conclusions……………………………………………………………..102

5.5 References……………………………………………………………...103

Chapter 6. Operando FTIR Spectroscopy ...... 105

6.1 Introduction……………………………………………………………..106

6.2 Experimental……………………………………………………………112

6.2.1 Materials ...... 112 6.2.2 Instruments ...... 112 6.2.3 Methodology ...... 115 6.3 Results and Discussion………………………………………………..118

6.4 Conclusions ……………………………………………………………..127

6.5 References……………………………………………………………...129

Chapter 7. X-Ray Absorption Spectroscopy Studies on the TS-1

Titanium Centre ...... 131

7.1 Introduction……………………………………………………………..132

7.1.1 Features of Titanium Silicalite-1 as Studied by XAFS ...... 132 7.1.2 Study of the TS-1-hydroperoxo Complex Using XAFS ...... 135 7.2 Experimental……………………………………………………………138

7.2.1 Materials ...... 138 7.2.2 Instruments ...... 138 7.3 Methodology…………………………………………………………….143 III

7.3.1 Sample Preparation ...... 143 7.3.2 Procedure ...... 144 7.4 Results and Discussion………………………………………………..147

7.5 Conclusions……………………………………………………………..154

7.6 References……………………………………………………………..156

Chapter 8. Conclusions, Recommendations and Further Work 159

List of Figures

Figure 1-1: Fuel shares of total primary energy supply (2018)[1]...... 2

Figure 1-2: Annual CO2 production from fossil fuels[3]. ■ Coal ■ Oil ■

Natural gas ...... 3

Figure 1-3: Reduction in emissions for biodiesel blends relative to conventional diesel fuels[5]...... 4

Figure 1-4: Projected global biodiesel production (billions of litres)[7]. . 5

Figure 1-5: Transesterification reaction for the production of biodiesel from triglycerides. R1,R2,R3 are hydrocarbon chains of 15 to 21 carbon atoms,

R4 is generally 1 to 2 carbon atoms long...... 7

Figure 1-6: Value-added products derived from glycerol...... 8

Figure 1-7: Reaction between dicarboxylic acid (acetic anhydride) and polyol (glycerol) to form alkyd resin. Colours indicate structural contributions from monomers. Glycidol may be substituted for glycerol...... 9

Figure 1-8: Nucleophilic addition to glycidol, where Nu is a suitable nucleophile and H-A is a Brönsted acid...... 10

Figure 1-9: Initiation of anionic ring-opening polymerisation of glycidol, where R is an alkyl chain of arbitrary length and M is an alkali metal, usually

Na, K or Cs...... 10

Figure 1-10: Propagation step in the polymerisation of glycidol...... 10

Figure 1-11: Substitution at the hydroxyl group, where X is a halogen or other electronegative atom and R is an alkyl group of arbitrary length...... 11

Figure 1-12: Energetic poly(GLYN) from nitrated glycidol derivative

(GLYN)...... 12

Figure 1-13: Meerwein-Ponndorf-Verley reaction showing the transfer of an acidic proton from an alcohol (isopropanol) to a carbonyl oxygen atom using aluminium isopropoxide catalyst...... 16

Figure 2-1: Simplified mechanism of ester hydrolysis by a homogeneous general acid catalyst (H-A)[30]. The proton transfer step between

III and IV has been omitted for conciseness...... 21

Figure 2-2: Energy Profile of a generic chemical reaction showing uncatalysed (blue) and catalysed (red) pathways, where Ea and ECat are the activation energies for the uncatalysed and catalysed reaction respectively.

...... 23

Figure 2-3: Reaction energy profile for a generic gaseous reaction, with the thermal reaction (blue) and catalysed reaction (red). E refers to the activation energies for the four main stages in the catalysed reaction referred to by subscripts corresponding to the catalysed reaction (c), the thermal reaction (t), reactant adsorption (a) and product desorption (d). ΔHa is the heat of adsorption of reactants and ΔHR is the overall heat of reaction...... 25

Figure 2-4: Langmuir-Hinshelwood model. First, reactants are adsorbed to the catalyst surface (a). Reactants then diffuse across the surface such that they are at a distance where interaction can occur (b). The product molecule formed then diffuses from the catalyst surface (c)...... 28

Figure 2-5: Eley-Ridley catalytic model where one reactant adsorbs onto the catalyst surface (a), which then interacts with a suitably nearby reactant (b), yielding the product (c)...... 28

Figure 2-6: General reaction rate-conversion curve for autocatalysed reaction, where rA is the reaction rate and XA is the conversion of species A.

...... 30

Figure 2-7: Ethylene oxide a), diethyl either b)...... 31

Figure 2-8: General allylic structure, where R is the rest of the molecule.

The sp3 hybridised carbon alpha to the double bond is referred to as the 'allylic' carbon...... 32

Figure 2-9: Conjugation of p orbital leading to resonance delocalisation in allylic structures...... 32

Figure 2-10: Transfer of oxygen atom from a hydroperoxide species to an unsaturated organic species to form an epoxide and alcohol...... 34

Figure 2-11: Oxidation of halohydrin to epoxide via olate mechanism.

...... 35

Figure 2-12: Glycerol carbonate synthesis from glycerol via a) urea and b) dimethyl carbonate routes and subsequent decarboxylation to glycidol. . 35

Figure 2-13: Sharpless epoxidation reaction. The active species is a titanium isopropoxide-tertiary peroxide complex, with enantiomeric selectivity determined by arrangement of the tartrate...... 37

Figure 2-14: Peroxo- and oxo- metal mechanistic pathways for transition metal catalysed epoxidation...... 39

Figure 2-15: LTA framework structure, also showing pore composition with representative dimensions (Å)[67]...... 40

Figure 3-1:Allyl alcohol epoxidation apparatus...... 50

Figure 3-2: Vibrational modes of water; a) bending, b) symmetric stretching, c) asymmetric stretching...... 52

VII

Figure 3-3: Schematic of FTIR spectrometer...... 53

Figure 3-4: Interferogram and its corresponding spectrum...... 54

Figure 3-5: XAS spectrum of Ti K edge. 1. Pre-edge region. 2. Pre-edge peak (present only in specific circumstances). 3. Edge. 4. Extended x-ray region...... 56

Figure 3-6: Elettra XAFS beamline optical scheme[81] ...... 58

Figure 4-1: Schematic of glycerol conversion reactor[16]...... 66

Figure 4-2: Effect of alkali metal loading on allyl alcohol and acrolein yields from glycerol conversion at 340°C and 180 min reaction time. The catalyst with no alkali metal treatment (iron oxide on alumina only) is shown in the last pair of columns[108]. Data for the plain alumina spheres is shown in the

“Nil” column for comparison...... 68

Figure 4-3: Proposed reaction mechanism for the DOHD of glycerol to allyl alcohol, including pathways to acrolein[108]...... 70

Figure 4-4: Glycidol concentration over course of epoxidation reaction with feed mixtures representative of the prior glycerol conversion reaction. 73

Figure 4-5: Glycidol concentration over course of epoxidation reaction with feed mixtures representative of the prior glycerol conversion reaction. 73

Figure 5-1: Electron distribution in the lowest energy highest occupied molecular orbital (HOMO) for propene a) and the effect of substituting a proton on the neighbouring carbon atom to the pi bond in propene for a strongly electron withdrawing group (alcohol) on the pi bond b)...... 78

Figure 5-2: Nucleophilic ring opening mechanism of glycidol (SN2 mechanism) in acid at the least hindered epoxy carbon (a.) and most hindered

VIII epoxy carbon (b.). In the case of the SN2 mechanism, attack at the least hindered epoxy carbon is favoured...... 79

Figure 5-3: SN1 ring-opening mechanism of glycidol. In this case the epoxide must be protonated first. In the case of attack by weaker nucleophiles including water and alcohols, nucleophilic attack at the most substituted epoxy carbon (b.) is favoured as the more stable carbocation (2°) is formed and produces the least substituted alcohol...... 79

Figure 5-4: Solvent-titanium hydroperoxide species...... 81

Figure 5-5: Data from Hutchings et al[94,95]. comparing allyl alcohol conversion (XAA), given in closed symbols, and selectivity to glycidol (SGlc), given in open symbols...... 82

Figure 5-6: Data from Hutchings et al.[94,95] comparing allyl alcohol conversion (XAA), given in closed symbols, and selectivity to glycidol (SGlc), given in open symbols...... 82

Figure 5-7: Mechanism for the epoxidation of allyl alcohol by hydrogen peroxide over TS-1...... 85

Figure 5-8: Epoxidation reaction glassware...... 88

Figure 5-9: XRD pattern of calcined titanium silicalite-1 (top) and reference pattern (bottom) ...... 89

Figure 5-10: Nitrogen adsorption isotherm at liquid nitrogen temperature

(top) and corresponding t-plot (bottom) for calcined TS-1...... 90

Figure 5-11: Allyl alcohol conversion with respect to reaction temperature...... 94

Figure 5-12: Glycerol formation during epoxidation reaction, 70°C. .. 95

Figure 5-13: Conversion of allyl alcohol (XAA) in the presence of additive species representative of process by-products. Additives are in equimolar quantities with allyl alcohol. Solvent volume was modified in order to maintain equivalent reaction volume across all experiments...... 97

Figure 5-14: Relative reaction rate as influenced by dipole moment of additive (calculated)...... 100

Figure 5-15: Proposed mechanism of rate enhancement by additive species, in this example acetaldehyde...... 101

Figure 5-16: Proposed mechanism for epoxidation inhibition by acrolein additive...... 101

Figure 6-1: Custom FTIR cell assembly...... 113

Figure 6-2: FTIR cell vacuum manifold...... 114

Figure 6-3: TS-1 catalyst before (blue) and after activation (red) at 723

K, with activated silicalite (black)...... 118

Figure 6-4: Background-corrected spectra of activated TS-1 (black), after peroxide addition (HP-TS-1) and vacuum applied for 6 hours (blue) and

HP-TS-1 after reheating to 723 K (red)...... 119

Figure 6-5: Difference spectra (calcined TS-1 subtracted) of peroxide- doped and re-heated TS-1 (black and red spectra respectively). Spectra have been normalised to framework vibrations at 1300-1000 cm-1 before subtraction...... 121

Figure 6-6: Background-corrected spectra of activated silicalite (black), after peroxide addition (HP-S-1) and vacuum applied for 6 hours (blue) and

HP-S-1 after reheating to 723 K (red)...... 121

Figure 6-7: Difference FTIR spectra following allyl alcohol adsorption on reheated HP-TS-1 shortly after (blue and green), five minutes after (red) and one hour (black) after AA addition...... 122

Figure 6-8: Increase in carbonyl stretch proportional to decrease in vinyl vibration (integrated band area)...... 123

Figure 6-9: Glycidol adsorbed onto TS-1 (difference spectrum)...... 124

Figure 6-10: Suggested isomerisation mechanism on ruthenium MOF catalyst, adapted from Scalambra et al[146]...... 125

[147] Figure 6-11: Isomerisation-tautomerism mechanism over Pd-TiO2 .

...... 126

Figure 7-1: Proposed oxidative species formation routes on an ideal

Ti(IV) site (a) and on a defect site (b) by condensation of a water molecule[170].

...... 135

Figure 7-2: η2 Ti-peroxo complex (coloured species, a) and η2 Ti- hydroperoxo complex obtained after dehydration of a. The η1 hydroperoxo complex would look more like the product(s) from Figure 7-1...... 137

Figure 7-3: Schematic of XAFS beamline at the Elettra Synchrotron[81].

...... 139

Figure 7-4: X-ray absorption cell assembly (window assembly insert).

...... 141

Figure 7-5: Beam paths in custom XAFS cell: a-FTIR, b-transmission

XAFS, c-fluorescence XAFS...... 142

Figure 7-6: XAFS experiment piping system...... 142

Figure 7-7: Depiction of targeting suitable position for the beam spot on a new wafer, ideal sample (left) and sample with a pinhole fault (right). .... 144

Figure 7-8: Experimental XAFS spectra for TS-1 under conditions per

Section 7.3.2; calcined (black); H2O2 / H2O added (red); re-calcined after peroxide addition (blue). Detail of pre-edge in inset...... 148

Figure 7-9: Fourier Transform of k2 weighted Χ(k) data (Χ(k) spectra provided in inset, more detailed figures in Error! Reference source not found.).

Calcined TS-1 shown in black, H2O2 / H2O doped TS-1 in red and re-calcined

TS-1 is shown in blue, or spectra a, b and c respectively in the inset. Broken lines indicate theoretical models...... 149

Figure 7-10: Difference spectra (calcined TS-1 subtracted) of peroxide- doped TS-1 sample (red) and after re-heating (blue). The persistence of the -

OH stretching band at ca. 3400 cm-1 indicates residual -OH species...... 152

Figure 7-11: Proposed structure of titanium species in this experiment in its native state (a), after aqueous peroxide addition (b) and after re-heating b (c)...... 153

XII

List of Tables

Table 1-1: Optically-active drugs obtainable from glycidol derivatives.

...... 13

Table 4-1: Product distribution from the conversion of glycerol (35 wt%

[108] in H2O) over alumina at 340°C ...... 67

Table 4-2: Ammonia TPD data for catalysts studied in Figure 4-2[16] 69

Table 4-3: Reaction feed composition and allyl alcohol conversion for different glycerol product distributions over 4 h...... 71

Table 5-1: Effect of solvent type on the conversion of allyl alcohol and corresponding selectivity to oxidation products. Reaction at 60°C...... 92

Table 5-2: Effect of reaction temperature on conversion and selectivity of epoxidation reaction on TS-1 in ethyl acetate solvent...... 93

Table 5-3: Yield of by-product in glycerol to allyl alcohol conversion using iron oxide on alumina...... 95

Table 5-4: Effect of additives to epoxidation reaction conversion and selectivity...... 98

Table 6-1: Band assignment for generic zeolite infrared spectra[127].

...... 107

Table 7-1: Summary of XANES (columns 2-4) and EXAFS fitting

(columns 6-9)...... 150

XIII