Electrochemical Conversion of Bio-Derived Dicarboxylic Acid Into High Value Added Chemicals Sanaz Abdolmohammadi Iowa State University

Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations

2018 Electrochemical conversion of bio-derived dicarboxylic acid into high value added chemicals Sanaz Abdolmohammadi Iowa State University

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Recommended Citation Abdolmohammadi, Sanaz, "Electrochemical conversion of bio-derived dicarboxylic acid into high value added chemicals" (2018). Graduate Theses and Dissertations. 17137. https://lib.dr.iastate.edu/etd/17137

This Thesis is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Electrochemical conversion of bio-derived dicarboxylic acid into high value added chemicals

Sanaz Abdolmohammadi

A thesis submitted to the graduate faculty

in partial fulfillment of the requirements for the degree of

MASTER OF SCIENCE

Major: Chemical Engineering

Program of Study Committee: Eric Cochran, Major Professor Jean-Philippe Tessonnier Chris Williams

The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this thesis. The Graduate College will ensure this thesis is globally accessible and will not permit alterations after a degree is conferred.

Iowa State University

Ames, Iowa

2018

TABLE OF CONTENTS

Page

LIST OF FIGURES ...... iii

LIST OF TABLES ...... v

ACKNOWLEDGMENTS ...... vi

ABSTRACT ...... vii

CHAPTER 1. INTRODUCTION ...... 1 1.1 Displacement of Petroleum Resources ...... 1 1.2 Integration of Bio and Chemical Catalysis ...... 1 1.3 Significance of bio-derived carboxylic acid in polymer industry ...... 3 1.3.1 Selective top 10 DOE aliphatic carboxylic acid ...... 4 1.3.2 Biopreviledged dicarboxylic acid ...... 6 1.4 Electro-Organic Synthesis ...... 7 1.5 Application of Bio-Derived Diacids in Polyamides Synthesis ...... 10 1.6 Current State of the Research ...... 11 1.7 Research Goal and Significance ...... 12

References ...... 13

CHAPTER 2. EXPERIMENTAL SECTION ...... 18 2.1 Polymer Synthesis ...... 18 2.2 Polymer Characterization ...... 18 2.2.1 Thermal properties measurement ...... 18 2.2.2 Mechanical properties measurement ...... 19 2.2.3 Wide-Angle X-ray Scattering (WAXS) ...... 19

CHAPTER 3. BIOADVANTAGED NYLON FROM RENEWABLE MUCONIC ACID: SYNTHESIS, CHARACTERIZATION AND PROPERTIES ...... 20 3.1 Introduction ...... 20 3.2 Combining Metabolic Engineering and Electrochemistry ...... 23 3.3 Production of Polyamides from Sugar: ...... 25 3.4 Results and Discussions ...... 26 3.5 Applications ...... 31 3.6 Conclusion ...... 33 3.7 Acknowledgments ...... 33

References ...... 34

CHAPTER 4. CONCLUSION AND FUTURE DIRECTION ...... 39 iii

LIST OF FIGURES

Page

Figure 1.1. Coupling of chemical and biological catalysis for production of biorenewable chemicals. Reproduced with permission from reference (12) ...... 2

Figure 1.2. Bio-based derived monomer from fermentation. Reproduced with permission from reference (18) ...... 3

Figure 1.3. Lactic acid as a platform molecule for the synthesis of chemical intermediates. Reproduced with permission from reference (2) ...... 5

Figure 1.4. Potential platform of succinic acid. Reproduced with permission from reference (2) ...... 6

Figure 1.5. Electrocatalytic hydrogenation mechanism of unsaturated substrates. Reproduced with permission from reference (37)...... 9

Figure 1.6. Overview of bio-based processes and building blocks for polyamides. Reproduced with permission from reference (8)...... 11

Figure 3.1. Value-added products obtained from biobased muconic acid. Reproduced with permission from reference (22)...... 22

Figure 3.2. (a) Electrochemical hydrogenation of MA to t-3HDA with five successive runs. (b) ECH of MA in acidic fermentation broth with pH of 2.0. Reproduced with permission from reference (21). Copyright © 2016, John Wiley and Sons ...... 24

Figure 3.3. Anticipated overall process flow diagram for the production of t-3HDA through fermentation and electrochemical hydrogenation. Reproduced with permission from reference (20). Copyright © 2016, American Chemical Society ...... 25

Figure 3.4. Nylon blends with various molar ratio of t-3HDA ...... 26

Figure 3.5. (a) DSC comparison of Nylon 6,6 and BAN samples from 25-300 ˚C. (b) TGA plot of comparison of Nylon 6,6 and BAN samples from 40- 700 ˚C ...... 28

Figure 3.6. WAXS patterns of Nylon 6,6 and BAN samples at room temperature ...... 30 iv

Figure 3.7. (a,b) TEM images of Nylon 6,6 and BAN 60, respectively. (c,d) Selected area electron diffraction (SAED) patterns of Nylon 6,6 and BAN 60, respectively...... 31

LIST OF TABLES

Page

Table 3.1. Storage modulus @ 30 ˚C and 1 Hz and α-relaxation temperature calculated from peak maxima in Tan δ ...... 29

ACKNOWLEDGMENTS

I would like to take this opportunity to express my gratitude to my professors, Eric

Cochran and Jean-Philippe Tessonnier who have provided me with great help and encouragement at every step in my research during last three years. Without their tremendous supports, the transition from Science to Engineering would not have been possible for me. I extend my special thanks to Professor Chris Williams for all the time and efforts he put on my dissertation.

My deeply thanks would go to my friends and collaborators, in both polymer group and catalysis group, Fang-Yi Li, Dr. Michael Forrester, and Austin Hohmann, who always helped me with their valuable advice. In particular, I would like to acknowledge all the great support, mentoring and guidance, that I received from Dr. John Matthiesen and Dr.

Nacu Hernandez especially during my first year; I will cherish their friendship for the rest of my life.

In addition, I would also like to thank Jake Nelson, Dustin Gansebom and Danielle

Thompson for their enthusiastic works. Last but not least, my sincere gratitude to my family and friends for their endless and warm assistance during the period of my study.

vii

ABSTRACT

Recently, from both environmental and economic points of view, green polymers

(or biobased polymers), which can be produced partially or entirely from renewable and

sustainable natural resources, is of growing interest compared to conventional petroleum-

based monomers and polymers. In this regard, lignocellulose biomass represents promising renewable source for production of renewable fuels, chemicals, organic solvent, and polymers.

Here, we present a new rout to convert bio-derived unsaturated dicarboxylic acid

via electrochemical hydrogenation into bioadvantaged monomer (trans-3 hexenedioic acid) that has a potential for synthesizing a new family of unsaturated polyamides

(bioadvantaged Nylon 6,6). A bioadvantaged nylon 6,6 was prepared via polycondensation reaction between trans-3 hexenedioic acid (t3-HDA), adipic acid (AA) and hexamethylendiamine (HMDA).

The produced bioadvantaged nylons were characterized by Differential Scanning

Calorimetry (DSC), thermogravimetric analysis (TGA), wide angle X-ray scattering

(WAXS), Transmission Electron Microscopy (TEM), Dynamic Mechanical Analyzer

(DMA). The results of thermal properties indicate that the addition of t3-HDA doesn’t change the thermal stability of bioadvantaged nylon, however, incorporation of t3-HDA can change the crystalline structure of Nylon 6,6 from semi-crystalline to amorphous. 1

CHAPTER 1. INTRODUCTION

1.1 Displacement of Petroleum Resources

Green (or biobased) polymers, which can be produced either partially or entirely from renewable natural resources, are of growing interest due to increased concern with conventional petroleum-based feedstocks.1 Currently, fossil fuel resources are the primary

source to produce of energy, chemicals, and polymers. Intensive consumption of petroleum- based compounds in industry and transportation sectors has led to accelerated rates of global

2-3 warming due to the release of CO2 into the atmosphere. In addition to detrimental effects on

the environment, the inevitable depletion of fossil fuel resources drives the search for more

affordable and “clean” alternative feedstocks.4-5

In this regard, biomass-derived feedstocks are plying an important role for production

of fuels, polymers, coatings, organic solvents, and adhesives. Among biomass feedstocks, lignocellulose received a lot of attention, as it is the most abundant, cheapest, and desirable feedstocks.6 In addition, having higher ratio of oxygen to carbon and hydrogen in lignocellulose feedstock compared to that of in petroleum based resources makes it relatively

more attractive for production of wide variety of chemicals.7 Hence, much effort have focused

on developing techniques for fractionation of lignosellulosic biomass into carbohydrates and

lignin and transformed into wide range of useful chemicals and material building blocks.8-11

1.2 Integration of Bio and Chemical Catalysis

Development of the technologies required for the transformation of biomass into diverse high value chemicals is challenging. Functionality of the target molecules as well as their atom efficiency are the key aspects in developing the conversion process. The general 2

approaches applied in transforming and upgrading of biomass into high value chemicals were

reported through either biological, chemo-catalytic, or hybrid technologies.12-13 Depends on potential of platform molecules, the choice of upgrading approach is varying and challenging.

Figure 1.1 illustrates the integration of biological and chemical catalysis as an effective process through which biomass selectively de-functionalized by biological catalysts into platform molecules and can further be upgraded to biobased chemicals through heterogeneous catalysis.14-16 However, due to residual biogenic impurities many challenges such as extensive

separation and purification as well as catalyst deactivation were reported with those routes for

transformation of biomass into oxygen-rich platform molecules.12-13

Figure 1.1. Coupling of chemical and biological catalysis for production of biorenewable chemicals. Reproduced with permission from reference (12)

1.3 Significance of bio-derived carboxylic acid in polymer industry

C5 and C6 carbohydrates have received much attention due to their unique oxygen-rich

structure and for their potential to be converted into wide variety of drop-in and novel chemicals. Sugar-derived carboxylic acid as a platform chemical can subsequently converted into intermediates, monomers, and polymers.2 The comprehensive potential application of

sugar-derived monomers in polymer industry were discussed previously.17 In this regards,

Figure 1.2 represents the wide range of biobased monomers produced by fermentation or bio

catalytic processes of carbohydrate feedstocks.18 In 2004 by the US Department of Energy

(DOE) selected some of the categorized biobased monomers as the top 12 chemical based on

their potential application and their market value.2

Figure 1.2. Bio-based derived monomer from fermentation. Reproduced with permission from reference (18)

1.3.1 Selective top 10 DOE aliphatic carboxylic acid

Carboxylic acid and dicarboxylic compounds, which can be derived from the biomass

via fermentation and hydrolysis, are widely applicable in a variety of industries such as food

and pharmaceutical, surfactants, detergents. In addition, they have been currently recognized

as of interest as a raw material for biodegradable polymers. Bio-derived carboxylic acids (e.g.

lactic acid, succinic acid, fumaric acid, malic acid, ... ) are considered important renewable

building blocks for production of polyester and polyamide.7 Below are some example of carboxylic acid compound derived from either the biological-chemical rout or the hybrid rout.

Lactic acid (LA) (2-hydroxypropionic acid) is mainly produced from the fermentation of different resources of carbohydrates like glucose or xylose using organisms such as

Lactobacillus delbrueckiia or Pichia stipites, respectively.19-20 Its two functional groups of

hydroxyl and carboxylic acid in a three-carbon molecule, possesses a high potential for chemical reactivity such as condensation, esterification, reduction and substitutaion.20 Figure

1.3 showed LA is a platform for production of valuable products through a variety of reactions.

A diverse set of applicable catalytic transformations enable primary production of a variety of

renewable and degradable thermoplastic polymer (e.g., PLA), and solvents (e.g., ethyl lactate),

plasticizers (e.g., butyl glycolate), and other oxygenated chemicals from LA.21-22

The interest in LA production as a building block for renewable biopolymer and high

value chemicals is rising, and it is estimated to be produced up to 600000 tons in 2020.

Despite the great attention LA has received, still efficient technologies for separation,

purification and conversion of it from fermentation broth is underdeveloped. Therfore, new

advances and developments in desalting, water splitting electrodialysis process, and chemical

catalysis are being tested to overcome some of the barriers.20, 22 5

Figure 1.3. Lactic acid as a platform molecule for the synthesis of chemical intermediates. Reproduced with permission from reference (2)

Succinic acid, an aliphatic dicarboxylic acid, can be obtained from different routes of

petroleum and biobased resources. Succinic acid conventionally produced from catalytic

hydrogenation of maleic anhydride as a petroleum based raw chemical; however, it can be

derived from fermentation of sugar using Anaerobiospirillum succiniciproducens as well as engineering pathway of Eschaerichia coli. Succinic acid is recognized as an important building block for production of wide variety of polymers, solvents, and high value chemicals.23

Figure 1.4 illustrates the potential platform of succinic acid. Due to existence of the

reactive dicarboxylic functional groups, it has a great potential for production of different

variety of polyamides, and polyesters via condensation reaction. Bio-based production of 1,4-

Butanediol (1,4-BDO),Tetrahydrofuran (THF), Poly (tetramethylen oxide) (PTMO),

Polyamide 4,6 (PA 4,6), Polyamide 4,10 (PA 4,10), Poly(ethylene succinate) (PES) and

poly(Butylene succinate) (PBS) from succinic acid will expanded the capacity of its market. 6

Therefore, it is estimated to have a growth of 637 kton/y by 2020 for bio based production of

succinic acid with the market value of $1.1 billion.7-8, 23

Figure 1.4. Potential platform of succinic acid. Reproduced with permission from reference (2)

1.3.2 Biopreviledged dicarboxylic acid

Unsaturated dicarboxylic such as muconic acid (MA), also known as 2,4-hexadiendioic

acid can be derived from carbohydrate as well as lignin fraction.24-25 MA is an intermediate for

catabolism of aromatic compounds that has not been listed on DOE’s Top 10 list, but it has

received enormous attention. Highly oxygenated dicarboxylic acid MA with the reactive

conjugated double bond is considered a renewable platform for production of vast variety of

monomers that can further act as building blocks for manufacturing of polyamides such as

nylon 6,6 and polyesters.26-27 Moreover, MA is recognized as a bioprivileged molecule, which

means it can be effectively converted to variety of chemicals, including both novel molecules

and drop-in replacements.28 Hence, MA can be partially hydrogenated to novel unsaturated

diacids as trans-3-hexendioic acid or completely hydrogenated to adipic acid .29 7

Adipic acid (AA) has a global market over 2.7 million tons per year and is mainly

applicable in manufacturing of nylon 6,6, as well as plasticizers in the production of polyvinyl

chloride (PVC) and polyvinyl butyral (PVB), therefore making it one of the most prevalent

dicarboxylic acid. However, conventional production of AA from petroleum-based resources

30 has negative environmental impacts due to production of nitrous oxide (N2O). Therefore, it

is necessary to develop alternative green pathways for the production of AA. Recent research

has broadly focused on environmental friendly approaches. However, the thermoscatalytic

conversion pathway requires use of high pressure H2, noble metal catalyst and a halogen

source. Therefore, electrochemical process plays important role for conversion of MA to AA.

In addition, to conversion of MA to large-scale commodity chemicals, it has potential to convert to a promising intermediate as t3HDA.

In summary, wide varieties of synthesized carboxylic acids and dicarboxylic acids have been reported from biorenewable feedstock. However, the choice of an efficient and cost effective approach for the existing technologies is still challenging. With respect, the next section will addressed some of the limitation reported in each processing route as well as will discuss about electrochemical hydrogenation pathway as an alternative for the existing processing route .

1.4 Electro-Organic Synthesis

Conventional technologies for upgrading biomass rely on either chemo-catalytic or biological route. Production of overabundance of target biobased chemicals make some limitation in each processing route. As a result, one approach to mitigate the extensive separation is combining electrocatalysis and biomass conversion. The electrocatalytic hydrogenation (ECH) pathway is considered as an alternative and sustainable route for bio- 8

derived intermediates hat can be carried out at ambient temperature and pressure. In ECH,

hydrogen is generated at the surface of the working electrode material (cathode) through the

hydrogen evolution reaction. In addition, removing problems with hydrogen transportation and

storage by in situ production of chemisorbed hydrogen as well as substitution of organic

solvent for water to make this method as a promising green approach for hydrogenation of

renewable chemicals in water. 31

These beneficial properties have increased tremendously interest on electrochemical

hydrogenation of “Top 10” biorenewable compounds that has been identified by U.S.

Department of Energy (DOE), such as levulinic acid, furanic compounds, lactic acid and bio-

oil derived phenolic compounds to produce drop-in biofuels and stabilize bio-oil. 32-35

For instance, Xin et al (2013)36 converted levulinic acid (LA) into veleric acid (VA)

and γ-Valerolactone (gVL) through a single Pb electrode-based electrocatalytic hydrogenation

(ECH) flow cell reactor with high selectivity, high Faradaic efficiency, and high electrical

energy storage, and requiring low electricity consumption. Qiu et al (2014) 33 coupled

electrocatalytic hydrogenation of LA using a bulk Pb electrode catalyst in a single flow cell

reactor with electrocatalytic oxidation of formic acid using a Pd/C anode catalyst in a proton

exchange membrane. In adittion, in another study, ECH of lactic acid (LA) only has been done

for hydrogenation of LA to 1,2 propanediol or propylene glycol(PG) which is one the important

commodity chemical and lactaldehyde. Dalavoy et al. (2007) performed mild electrocatalytic

hydrogenation of lactic acid using 5% Ru/C powder catalyst; results indicate that selectivity of

the products is current and pH sensitive.37 Those findings acknowledge the electrocatalytic

biorefinery process as both promising and challenging. 9

As mentioned, one of the main advantageous of the electrocatalytic hydrogenation

process is production of chemisorbed hydrogen from different sources, either solvent or

supporting electrolyte. The general mechanism of ECH is described by Equations 1 through

4.38-39

H2 + 2M 2MHads (1)

+ - H3O + e↔+ M MHads+H2O (Volmer) (2)

2MHads 2M+H→2 (Tafel) (3)

+ - H3O +MH→ ads +e M+H2+H2O (Hyrovsky) (4)

Fig. 5. describes→ the several steps of ECH of unsaturated of organic compounds. Based

on the fact that ECH involves reaction of hydrogen with unsaturated organic molecule,

adsorbing on the cathode surface followed by desorption of the hydrogenated product. In this

regard, there is competition between hydrogenation and desorption steps that can be controlled

by several parameters such as pH, adjustment of current density, supporting electrolyte, and

designing cathode catalyst.37

Figure 1.5. Electrocatalytic hydrogenation mechanism of unsaturated substrates. Reproduced with permission from reference (38).

The component of an electro-organic system consist of an electrolyte, electrodes (anode

and cathode), organic reactants, and voltage. The reaction can happen in either divided cell or

undivided cell. In an electrochemical cell, the voltage is a driving force for the reaction, while

the electrolyte play important role as an ion conductor for transporting electrons between the

electrodes and organic reactant. Based on the organic reactants, different kind of solvent can

be used such as methanol, acetonitrile, etc. The two electrodes, which are defined as cathode

and anode, act as a source of electrons. Essentially, reduction reaction can happen on the

cathode, and oxidation occur on the anode.31

1.5 Application of Bio-Derived Diacids in Polyamides Synthesis

Polyamides are engineering plastics produced from polycondensation of dicarboxylic acids and diamines. In polyamides, monomers are connected together with amide formation and water elimination process.40-42 Polyamides are semi-crystalline material with several

advantageous such as high strength, abrasion resistance, good barrier properties, and heat

resistance.43 Figure 1.6 illustrated different variety of biobased polyamides produced from bio-

based building blocks from biomass feedstocks and oil crops.

Among those, Nylon 6,6 is selected because it is a versatile thermoplastic polyamide

used for various applications as automotive parts, electronics, food packaging as well as high-

strength fiber or at elevated temperature. Same as other polyamides, Nylon 6,6 is a semi

crystalline polymer with 50-55% of degree of crystallinity which is due to strong hydrogen

bonding.44-46 Earlier in 1936, Nylon 6,6 was developed by Carothers and DuPont from

polycondention reaction of adipic acid (AA) and hexamethylendiamine (HMDA).47-48 11

Figure 1.6. Overview of bio-based processes and building blocks for polyamides. Reproduced with permission from reference (8).

1.6 Current State of the Research

Despite of all of the advantageous, Nylon 6,6 same as other polyamides has

hygroscopic property which make it sensitive to water absorption. As a result, the mechanical

properties such as strength and stiffness are significantly affected by moisture absorption.

As discussed earlier great interest in replacing green alternatives to petroleum-based

polymers, this part of study present a value opportunity of bio-advantaged polymers that can

be derived from biological monomer such as MA. Therefore, conversion of MA to a promising

intermediate monomer as trans-3-hexendioic acid (t3-HDA) via green pathway as electrochemical process receive a lot of attention. The unique structure of t3-HDA, makes it a 12 promising monomer to produce bio-advantaged nylon. The existence of double bond in t3-

HDA gives opportunity that can be used in the polymer backbone compared to AA and enable subsequent functionalization of polyamide followed by introducing novel properties through further chemical modifications.

1.7 Research Goal and Significance

This research project aims to study the electrochemical hydrogenation of alkenyl (C=C) functionalities of biorenewable molecules and their conversion into bio-based chemicals that can further act as building blocks for synthesizing of novel polymers with tailored properties.

Therefore, Chapter 2 will be related to the methodology and characterization of the structure, thermal and mechanical properties of bioadvantaged polyamide. Chapter 3 will review the key conditions for synthesizing unsaturated diacid t3-HDA via electrochemical hydrogenation of muconic acid and it will focus on the potential application of t3-HDA in replacing of adipic acid (AA) as monomer for synthesis of unsaturated polyamide such as nylon 6,6and comparing the properties against the conventional nylon.

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35. Li, Z.; Kelkar, S.; Raycraft, L.; Garedew, M.; Jackson, J. E.; Miller, D. J.; Saffron, C. M., A mild approach for bio-oil stabilization and upgrading: electrocatalytic hydrogenation using ruthenium supported on activated carbon cloth. Green Chemistry 2014, 16 (2), 844- 852.

36. Xin, L.; Zhang, Z.; Qi, J.; Chadderdon, D. J.; Qiu, Y.; Warsko, K. M.; Li, W., Electricity storage in biofuels: selective electrocatalytic reduction of levulinic acid to valeric acid or gamma-valerolactone. ChemSusChem 2013, 6 (4), 674-86.

37. Dalavoy, T. S.; Jackson, J. E.; Swain, G. M.; Miller, D. J.; Li, J.; Lipkowski, J., Mild electrocatalytic hydrogenation of lactic acid to lactaldehyde and propylene glycol. Journal of Catalysis 2007, 246 (1), 15-28.

38. Lima, M. V.; Menezes, F. D.; de Barros Neto, B.; Navarro, M., A factorial design analysis of (+)-pulegone electrocatalytic hydrogenation. Journal of Electroanalytical Chemistry 2008, 613 (1), 58-66.

39. Vilar, M.; Oliveira, J. L.; Navarro, M., Investigation of the hydrogenation reactivity of some organic substrates using an electrocatalytic method. Applied Catalysis A: General 2010, 372 (1), 1-7.

40. Keith, M., Polyamides – Still Strong After Seventy Years. Macromolecular Reaction Engineering 2011, 5 (1), 22-54.

41. Russo, S.; Casazza, E., 4.14 - Ring-Opening Polymerization of Cyclic Amides (Lactams) A2 - Matyjaszewski, Krzysztof. In Polymer Science: A Comprehensive Reference, Möller, M., Ed. Elsevier: Amsterdam, 2012; pp 331-396.

42. Katja, S.; Ute, S., Polyamides as Artificial Transcription Factors: Novel Tools for Molecular Medicine? Angewandte Chemie International Edition 2004, 43 (19), 2472-2475.

43. Winnacker, M.; Rieger, B., Biobased polyamides: recent advances in basic and applied research. Macromolecular rapid communications 2016, 37 (17), 1391-1413.

44. Vasanthan, N., Crystallinity Determination of Nylon 66 by Density Measurement and Fourier Transform Infrared (FTIR) Spectroscopy. Journal of Chemical Education 2012, 89 (3), 387-390.

45. Navarro-Pardo, F.; Martínez-Barrera, G.; Martínez-Hernández, A. L.; Castaño, V. M.; Rivera-Armenta, J. L.; Medellín-Rodríguez, F.; Velasco-Santos, C., Effects on the thermo- mechanical and crystallinity properties of nylon 6, 6 electrospun fibres reinforced with one dimensional (1D) and two dimensional (2D) carbon. Materials 2013, 6 (8), 3494-3513.

46. Ma, Y.; Zhou, T.; Su, G.; Li, Y.; Zhang, A., Understanding the crystallization behavior of polyamide 6/polyamide 66 alloys from the perspective of hydrogen bonds: 17 projection moving-window 2D correlation FTIR spectroscopy and the enthalpy. RSC Advances 2016, 6 (90), 87405-87415.

47. Carothers, W. H.; Berchet, G. J., STUDIES ON POLYMERIZATION AND RING FORMATION. VIII. AMIDES FROM ε-AMINOCAPROIC ACID. Journal of the American Chemical Society 1930, 52 (12), 5289-5291.

48. Smith, J. K.; Hounshell, D. A., Wallace H. Carothers and Fundamental Research at Du Pont. Science 1985, 229 (4712), 436-442.

CHAPTER 2. EXPERIMENTAL SECTION

2.1 Polymer Synthesis

A bioadvantaged nylon (BAN) was prepared via a polycondensation reaction between trans-3 HDA (t3-HDA), adipic acid (AA) and hexamethylendiamine (HMDA). Adipic acid

(AA) and trans-3 HDA (t3-HDA) with the molar ratio of x : (1-x), respectively, were both

dissolved separately in methanol (CH3OH), and afterward the resulting mixture with 1:1 molar

ratio were mixed with HMDA, which was dissolved in CH3OH. Then the reactant was heated

in a round bottom flask at 60 ˚C. The precipitated salt, which was formed within 20 min, was

filtered, washed three times with CH3OH and left to dry in a fume hood. To complete

polycondensation, the resulting salt was mixed with DI water with a mass ratio of 0.86:1,

placed into aluminum pan in a tube furnace, heated at the rate of 7.5 ˚C/min to 250-270 ˚C,

kept for 30 min under N2 purge, and then cooled to room temperature.

2.2 Polymer Characterization

2.2.1 Thermal properties measurement

Thermal studies were performed using thermogravimetric analysis (TGA) and

differential scanning calorimetry (DSC). TGA measurement of all samples were carried out

using a simultaneous thermogravimetry NETZSCH STA model STA 449 F1 Jupiter, on 3-5

mg weight samples in a alumina crucible pan with a heating rate of 10 ˚C/min from room

temperature to 700 ˚C. Experiments carried out under nitrogen atmosphere with flow rate of

20 mL/min. DSC of polymer powder were conducted using a DSC Q2000 (TA Instruments)

in aluminum hematic pans by cycling of heating and cooling between 0 and 300 °C, at

heating/cooling rates of 10 °C/min under N2 atmosphere with flow rate of 50 mL/min. 19

2.2.2 Mechanical properties measurement

Dynamic mechanical analysis (DMA) was performed using a TA instrument ARES-

G2 rheometer with a 3-point bending fixture under liquid nitrogen gas flow to prevent thermal degradation of polymer. All the samples were cut into test specimens with dimensions of 29 x

5 x 1 mm using Carver hydraulic press. To determine storage and loss modulus of samples, various temperature range from -30 to the practical limit of the sample’s melting point at a heating rate of 5 ˚C/min, a strain of 0.05% and frequency of 1 Hz was applied.

2.2.3 Wide-Angle X-ray Scattering (WAXS)

The crystalline structure of all powder of nylon samples was studied by wide angle X- ray scattering (WAXS) using a XENOCS Xeuss 2.0 SWAXS system with X-ray wavelength of λ = 1.542 Å from Cu Κα radiation. 20

CHAPTER 3. BIOADVANTAGED NYLON FROM RENEWABLE MUCONIC ACID: SYNTHESIS, CHARACTERIZATION AND PROPERTIES

Sanaz Abdolmohammadi,1 Nacú Hernández,1 Jean-Philippe Tessonnier,1,2 and Eric W. Cochran 1,*

1Department of Chemical and Biological Engineering, Ames, Iowa 50011, United States

2NSF Engineering Research Center for Biorenewable Chemicals (CBiRC), Ames, Iowa 50011, United States

*E-mail: [email protected]

We present a new route for converting glucose into a bioadvantaged monomer through

a hybrid process combining biological and chemical conversions. This monomer gives access

to a new family of unsaturated polyamides (bioadvantaged Nylon 6,6) with superior

performance compared to their petrochemical counterparts. Specifically, we demonstrate that

this chemical enables the introduction of new functionalities, hereby facilitating the synthesis

of Nylon 6,6 with tailored functional properties.

3.1 Introduction

The adverse effects of fossil carbon on the environment are driving the search for

alternative, more sustainable, feedstocks for the production of fuels and chemicals. In this

regard, biomass represents a promising source of renewable carbon for the synthesis of a wide

variety of monomers and polymers.1-2 Hence, bio- and chemocatalytic routes are being

developed to fractionate biomass into carbohydrates and lignin followed by their conversion

into oxygen-rich platform molecules.1, 3-11

Dicarboxylic acids are a large class of oxygen-rich molecules that can be produced via biological catalysis and that have a wide variety of applications spanning plastics, coatings and 21

adhesives.12-13 These broad applications attracted many researchers and encouraged them to

explore new pathways for the production and utilization of biobased diacids.14-19 Hybrid processes combining biological and chemical conversions have emerged as an effective strategy for building-block diversification.7-8 For this strategy, sugars are first converted to a

platform intermediate through fermentation using metabolically-engineered bacteria or yeast.

The biologically-produced intermediate is then further converted to the target diacid using a

chemical or chemocatalytic step. However, challenges associated with separation and

purification costs, low conversion rates as well as catalyst deactivation were reported while

trying to transform biomass into higher value compounds.8, 20 It is to mitigate these issues that

electrochemistry was proposed as an alternative to conventional chemocatalytic conversions,

in particular for hydrogenation reactions.20-22

Electrochemical hydrogenation (ECH) offers several key advantages for the conversion of biologically-derived intermediates. In ECH, hydrogen is generated at the surface of the working electrode material (cathode) through the hydrogen evolution reaction.23-25 This

approach suppresses the mass transfer limitations typical for 3-phase reactions and replaces

natural gas by water as a source of hydrogen.26-29 In addition, the Earth-abundant metals used

as electrode materials are resistant to biogenic impurities, thus offering opportunities to convert

the intermediate directly in the fermentation broth without any separation, which significantly

drops the production costs.21

Muconic acid (MA), a biologically-produced C6 diunsaturated dicarboxylic acid, has recently been identified as a biopreviledged molecule.30 The structure of this platform

compound makes it a unique intermediate for the production of both drop-in monomer

replacements and novel chemicals (Figure 3.1).17, 22, 30-35 22

Figure 3.1. Value-added products obtained from biobased muconic acid. Reproduced with permission from reference (22).

Full hydrogenation of MA yields adipic acid (AA), the most prevalent dicarboxylic acid with a global market size over 2.7 million tons per year. AA is mainly used as a monomer in the manufacturing of Nylon 6,6 and as a plasticizer in the production of polyvinyl chloride

(PVC) and polyvinyl butyral (PVB).30, 36-38

In addition to conversion of MA to large-scale commodity chemicals, electrochemistry gives access to promising novel species, including the monounsaturated monomer trans-3- hexenedioic acid (t-3HDA).20-22 The presence of a double bond advantageously positioned in the center of t-3HDA provides opportunities for insertion in the Nylon backbone and subsequent functionalization, hereby introducing novel properties in a commodity polymer. So far, t-3HDA is not easily accessible from petrochemical building blocks, but it is obtained through electrochemical hydrogenation of MA with selectivity and yield of higher that 94%.22 23

Hence, biomass provides new opportunities for the synthesis of bio-advantaged polymers with

superior functional properties compared to its parent polymer derived from petroleum.

3.2 Combining Metabolic Engineering and Electrochemistry

Recently, we have reported a unique approach of utilizing an engineered strain of

Saccharomyces cerevisiae yeast for the conversion of sugar into MA with the highest MA titer

reported in yeasts.21 Furthermore, this biologically-derived MA was converted into the

bioadvantaged monomer t-3HDA with 94% yield through the electrochemically hydrogenation

pathway in the presence of biogenic impurities, without any separation step and at low pH.21

Our successful electrochemical hydrogenation of MA to t-3HDA with optimized condition is

illustared in Figure 3.2. As a summary, the reaction was carried out in a three-electrode jacketed cell at room temperature and atmospheric pressure. The total reaction time was 1 h and the progress of the reaction was monitored by withdrawing 0.5 mL samples at 5, 15, 30 and 60 min for high performance liquid chromatography (HPLC) and 1H NMR analysis. The

fermentation broth was electrochemically hydrogenated by potentiostatic control with applied

potential of -1.5 V vs Ag/AgCl on a 10 cm2 lead rod. Lead was chosen as an electrode material

(working electrode) due to its Earth abundance, low cost, and resistance to biogenic impurities.

Figure 3.2 (a) shows a 95% conversion of MA and 81% selectivity of t-3HDA within one hour, as well as no evidence of catalyst deactivation within the 5 successive runs. Figure 3.2

(b) shows the yield under the optimized reaction conditions using the fermentation broth as a substrate. According to the results, slightly higher MA conversion 96 ± 2% with 98 ± 4% selectivity towards t-3HDA is reported in acidic media with the pH of 2.00.

(a) (b)

In addition, with the basis of the current yield and MA titer, our early stage technoeconomic analysis revealed that the cost for production of t-3HDA could be approximately at $ 2.00 Kg-1. Hence, the low production cost of t-3HDA will be one of the key

parameters of hybrid metabolic engineering and electrochemical hydrogenation. Figure 3.3

shows the process flow diagram for the production of t-3HDA used in the technoeconomic

analysis (TEA).20

To investigate more on the effect of bioadvantaged monomers as the backbone of polymers, t-3HDA replaced adipic acid as the monomer used in the synthesis of unsaturated polyamides, such as Nylon 6,6.

3.3 Production of Polyamides from Sugar:

Hence, a bioadvantaged Nylon (BAN) was prepared via a polycondensation reaction between t-3HDA, AA and hexamethylenediamine (HMDA). AA and t-3HDA with the molar ratio of x:(1 x), respectively, were both dissolved separately in methanol (CH3OH), and the resulting solution was mixed with a 1:1 molar ratio with HMDA dissolved in CH3OH. Then the reactants were heated in a round bottom flask at 60 ˚C. The precipitated salt was filtered, washed with CH3OH and left to dry in a fume hood. To complete the polycondensation, the resulting salt was mixed with DI water and heated up to 250-270 ˚C under N2 purge, and then cooled to room temperature.21 The differences in the color and physical properties of bioadvantaged Nylon compared to Nylon 6,6 are shown in Figure 3.4. BAN samples are named 26

based on the molar ratio of t-3HDA. Increasing the amount of t-3HDA changed the color of

Nylon 6,6 from translucent to clear for BAN100.

Figure 3.4. Nylon blends with various molar ratio of t-3HDA

3.4 Results and Discussions

Thermal characterization was performed using differential scanning calorimetry (DSC)

and thermogravimetric analysis (TGA). DSC of the polymer powder was conducted using a

DSC Q2000 (TA Instruments) in aluminum hematic pans by three consecutive heating and

cooling cycles between 25 and 300 °C, at a heating-cooling rate of 10 °C/min under a 50 mL/min N2 flow. TGA measurement of all samples were carried out using a NETZSCH model

STA 449 F1 Jupiter thermogravimetric analyzer, on 3-5 mg samples placed in alumina

crucibles. The samples were heated from room temperature to 700 ˚C with a heating rate of 10

˚C/min. Nitrogen with a flow rate of 20 mL/min was used to maintain an inert atmosphere.

Thermal properties of Nylon 6,6 and BAN samples are shown in Figure 3.5. Differential

scanning calorimetry (DSC) results in Figure 3.5 (a) illustrate that the existence of the

unsaturated double bond decreases the melting point for bioadvantaged Nylon. Commercial

Nylon 6,6 exhibited a melting temperature (Tm) of 253˚C, however, for BAN 50 the Tm 27

decreased to 172 ˚C. This phenomenon is attributed to the incorporation of t-3HDA into the polymer structure disrupting the crystalline structure of polymer, resulting in the reduction of

39-41 the Tm. The decrease of about 81˚C in the melting point of BAN 50 makes it suitable for

applications that require lower processing temperatures. Above 50% of t-3HDA loading, the

DSC trace of BAN 100 shows the existence of only a glass transition temperature (Tg) at 59

˚C and no visible Tm, indicating an amorphous structure of the bio-based polyamide.

Unfortunately, DSC is not sensitive enough for detection of glass transition temperature of polyamide, therefore, further investigation has been done using DMA studies.

Figure 3.5 (b) shows the thermal decomposition of Nylon 6,6 and BAN samples.

Similar to saturated Nylon 6,6, the unsaturated bioadvantaged Nylon has the same decomposition temperature range between 320 to 500 ˚C.42 With the addition of unsaturated

bonds in the structure of Nylon, the thermal stability of the bioadvantaged Nylon determined

at 50% weight loss of sample (Td50) slightly shifts to higher temperature. The value of Td50

varies from 431 ˚C for Nylon 6,6 to 447˚C for BAN 50 and 452 ˚C for BAN 100. The higher

value of Td50 for BAN samples shows the addition of t-3HDA has no negative affect on stability of the polyamide structure.41 The higher stability temperature makes bioadvantaged

Nylon a good candidate for melt processing.

100 Nylon 6,6 BAN 50 BAN 100 100 Nylon 6,6 BAN 50 80 BAN 100 80

60 60

Mass loss (wt%) loss Mass 40 Mass loss (wt%) loss Mass 20 20

0 0

100 200 300 400 500 600 700 100 200 300 400 500 600 700 Temperature (°C) Temperature (°C)

(a) (b)

Figure 3.5. (a) DSC comparison of Nylon 6,6 and BAN samples from 25-300 ˚C. (b) TGA plot of comparison of Nylon 6,6 and BAN samples from 40-700 ˚C

The mechanical behavior of the samples was determined using the Dynamic

Mechanical Analyzer (DMA) mode of a TA ARES-G2 instrument. Two unsaturated BAN

samples, one semi-crystalline (BAN 50) and one amorphous (BAN 100) were compared with

semi-crystalline Nylon 6,6. The storage modulus (E’) and the α-relaxation temperature (Tα) are summarized in Table 1. Nylon 6,6 shows the highest storage modulus compared to BAN

50 and BAN 100 which is due to the higher degree of crystallization of Nylon 6,6 compared to amorphous BAN 100.43 Incorporation of t 3HDA in the BAN structure has an effect on the

chain mobility of the polymer, resulting in a decrease in the α-relaxation temperature when

increasing t-3HDA content.

Table 3.1. Storage modulus @ 30 ˚C and 1 Hz and α-relaxation temperature calculated from peak maxima in Tan δ

Sample Storage modulus (MPa) α-relaxation temperature

(˚C)

Nylon 6,6 2.45 ˟ 103 ± 515 62.43 ± 2.02

BAN 50 1.24 ˟ 103 34.02 ± 0.23

BAN 100 5.41 ± 3.13 23.03 ± 1.64

The crystalline structure of BAN samples and Nylon 6,6 was studied by wide angle X- ray scattering (WAXS) using a XENOCS Xeuss 2.0 SWAXS system with X-ray wavelength of λ = 1.542 Å from Cu Κα radiation. Figure 6 shows WAXS data comparing Nylon 6,6 and

BAN samples at room temperature. The diffractogram of BAN 50 is very similar to that of

Nylon 6,6 consisting of both an amorphous and a crystalline part. The two characteristic peaks of Nylon 6,6 which are approximately at a q of 1.42 and 1.64 (Å-1), corresponding to (100) and

(010)/(110) doublet, respectively. These characteristic peaks correspond to intrasheet and

intersheets scattering and represent the α-phase of the triclinic Nylon 6,6.44-46 Upon the addition of t-3HDA, the intensity of the (010/110) peak decreases, which translates into a lower crystallinity for BAN 50 compared to Nylon 6,6. Further addition of unsaturated diacid completely diminishes the (010/110) peak, indicating a change in crystallinity from semicrystaline Nylon 6,6 and BAN 50 to amorphous BAN 100. DSC data corroborate these

results as above 50 % t-3HDA loading the DSC curve only shows a glass transition, in

agreement with an amorphous structure. 30

Nylon 6,6 BAN 50 BAN 100

1.0 1.5 2.0 2.5 3.0 q (A-1)

Figure 3.6. WAXS patterns of Nylon 6,6 and BAN samples at room temperature

Figure 3.7 shows TEM images of Nylon samples with less than 50% of t-3HDA loading

(Nylon 6,6) as well as more than 50 % of t-3HDA loading (BAN 60). The TEM grids were prepared by dispersing the samples in 1,4 butanediol, and placing a droplet of the Nylon dispersion on the TEM grid followed by drying in a vacuum oven at 60 ˚C. In Figure 3.7 (a) there is an obvious existence of crystalline structure in Nylon 6,6, by showing sheet-like formation which is randomly dispersed in the structure.47 However, increasing t-3HDA to approximately 60% formed aggregation in the structure of BAN 60 without any sheet-like thin film dissociation, see Figure 3.7 (b). In addition, Figure 3.7(c) shown, there is some orientation in the electron diffraction pattern of Nylon 6,6 samples, which can be attributed to the semi- crystalline structure of Nylon 6,6; however, in Figure 3.7 (d) existence of the circular halo ring is corresponding to the amorphous structure. These apparent differences in the structure of

Nylon samples is supported by the WAXS studies presented above. 31

(a) (b)

( c ) (d)

Figure 3.7. (a,b) TEM images of Nylon 6,6 and BAN 60, respectively. (c,d) Selected area electron diffraction (SAED) patterns of Nylon 6,6 and BAN 60, respectively.

3.5 Applications

Nylon 6,6 is selected because this polyamide has the capability of being synthesized from bio-based derived monomers. Nylon 6,6 is a versatile polyamide produced from 32

polycondensation of adipic acid and hexamethylenediamine. It is used for various applications

such as automotive parts, electronics, food packaging as well as high-strength fiber or at elevated temperature.42, 48-49 Despite all advantages of Nylon such as resistance to high

temperatures and chemicals, processing flexibility, and toughness, there are some drawbacks,

for example moisture absorption and poor surface wettability.50 The alkene bond in the structure of t-3HDA is amenable to a variety of functionalization startegies; thus, adding t-

3HDA to Nylon 6,6 forms a novel bioadvantaged Nylon.

As discussed earlier, there is great interest in replacing petroleum-based polymers by

green alternatives. This study presents a value opportunity for bioadvantaged polymers derived

from biological monomers such as MA. Even though research has thoroughly investigated the

conversion of MA to t-3HDA, subsequent and potential utilization of t-3HDA in polymers has

received less attention. Therefore, the focus of our work is on utilization of unsaturated diacid

(t-3HDA) in a polymer backbone and making unsaturated polyamide. The existence of unsaturated bond in bioadvantaged nylon can enable functionalization of double bond through sulfur vulcanization, or crosslinking, and the attachment of different chemical groups via thiol- ene chemistry. Therefore, it can enhance polymer properties, such as hydrophobicity, flame resistance, and antistatic.20,39 Figure 3.8 displays potential application of t-3HDA in the functionalization of unsaturated polyamide.

3.6 Conclusion

Overall, this study demonstrates production of a bio-derived monomer and its incorporation into a novel bioadvantaged polyamide. In addition, as a broader impact, this work provides a

basis for gaining new insight into electrochemical hydrogenation reactions of other

biorenewable compounds. Moreover, it involves determination of key conditions and

parameters in both selective electrochemical hydrogenation and polymerization processes (e.g. choice of catalyst, concentration of the media, pH, and temperature) to synthesize bioadvantaged polymers with enhanced properties.

3.7 Acknowledgments

This material is based upon work supported in part by the National Science Foundation EEC-

0813570, CBET-1512126, IIP-1701000, NSF-DMR 1626315. Research at the Ames

Laboratory was supported by the U.S. Department of Energy-Laboratory Royalty Revenue

(DE-AC02-07CH11358).

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CHAPTER 4. CONCLUSION AND FUTURE DIRECTION

Electrochemical conversion is an emerging pathway for biomass conversion, and the application of that for producing cost effective bio derived monomers, which are not

commercially available or difficult to process has received much attention. In addition,

electrochemical conversion is recognized as an economically feasible pathway through which

some separation steps can be eliminated, hence energy consumption will be decreased.

Overall, this study demonstrates the successful production of unsaturated bio-derived

monomers such as t-3HDA as well as implementation of the monomer into polyamide

backbone. The existence of double bond in t-3HDA gives opportunity that can be used in the

polymer backbone compared to AA and enable subsequent functionalization of polyamide

followed by introducing novel properties through further chemical modifications.

Functionalization of double bond through sulfur vulcanization, or thiol-ene reaction can

enhance some properties of polymers, such as hydrophobicity, flame resistance, and antistatic.