Supercritical Water Gasification of Two-Carbon Carboxylic Acid Derivatives

Home , Acetamide, Sabatier reaction

A thesis presented to

the faculty of

the Russ College of Engineering and Technology of Ohio University

In partial fulfillment

of the requirements for the degree

Master of Science

Matthew T. Conley

December 2018

This thesis titled

Supercritical Water Gasification of Two-Carbon Carboxylic Acid Derivatives

MATTHEW T. CONLEY

has been approved for

the Department of Chemical and Biomolecular Engineering

and the Russ College of Engineering and Technology by

Sunggyu Lee

Professor, Chemical and Biomolecular Engineering

Dennis Irwin

Dean, Russ College of Engineering and Technology 3

ABSTRACT

CONLEY, MATTHEW T., M.S., December 2018, Chemical Engineering

Supercritical Water Gasification of Two-Carbon Carboxylic Acid Derivatives

Director of Thesis: Sunggyu Lee

The dominant means of energy production today consist of the use of nonrenewable and environmentally harmful fossils that cannot be used for eternity.

Alternative energy sources are needed to combat the use of these fossil fuels and to one day replace them altogether. One potential fuel source is synthesis gas that can be derived from biomass and biomass waste. A production method for this synthesis gas is in the form of supercritical water gasification (SCWG). While SCWG is a relatively well- known process on a macro-level, little is known about the process at a molecular level.

This work focuses on the study of the SCWG of three different two-carbon carboxylic acid derivatives – acetaldehyde, acetic acid, and acetamide – to get a better understanding of the gasification process itself.

SCWG reactions were run on the three feedstocks in a custom built, high nickel alloy reactor at temperatures of 650 °C and 3600 psi with a residence time of 30 seconds. Gaseous products were quantified and analyzed via gas chromatography to determine reaction parameters such as composition, yield, and gasification rate.

Acetaldehyde had hydrogen yields of about 1.1 to 1.7 moles H2 per mole acetaldehyde fed while acetic acid and acetamide had yields of around 0.02 moles H2 per mole reactant. It was determined that the process of SCWG of carbonyl groups seemingly follows the same reactivity trend as that of general nucleophilic attack of carbonyls, which makes it likely that the SCWG of carbonyls occurs via the nucleophilic attack of water towards these carbonyl groups. 4

DEDICATION

To my family, whose support through the years has made me the person I am today and

has allowed for me to finish this work. 5

ACKNOWLEDGMENTS

First, I would like to express my gratitude towards my advisor, Dr. Sunggyu Lee, whose guidance and support has allowed for the completion of this work.

I would like to acknowledge Dr. Oludamilola Daramola who came in and exceptionally guided the SEAM Lab during Dr. Lee’s absence.

Chad Able, Hamed Bateni, and Greg Horne provided guidance, knowledge, and friendship throughout my time at the SEAM Lab, even after they left to pursue other opportunities and for that I am extremely grateful.

I would like to thank all of my professors that I have had throughout the years as they provided me with the knowledge needed to become the researcher that I am today.

To all of my friends, whether we’ve been friends for many years or for a short period of time, you have been with me throughout this journey and have made my time in my undergraduate and graduate studies enjoyable and for that I thank you.

Last but certainly not least, I would like to thank everyone who has worked at the

SEAM Lab past and present, from undergraduate students to graduate students. You have all provided help at times and for that I am extremely grateful.

TABLE OF CONTENTS

Page

Abstract ...... 3

Dedication ...... 4

Acknowledgments...... 5

List of Tables ...... 8

List of Figures ...... 9

Chapter 1: Introduction ...... 12

Chapter 2: Literature Review ...... 18

Chapter 3: Significance and Objectives ...... 21

Chapter 4: Experimental Methodology ...... 23

Section 1: Experimental Apparatus and Chemical Feedstocks ...... 23 Section 2: Experimental Design ...... 27 Chapter 5: Results and Discussion ...... 32

Section 1: Acetic Acid ...... 32 Section 2: Acetaldehyde ...... 43 Section 3: Acetamide ...... 49 Section 4: Connecting Trends ...... 54 Chapter 6: Conclusions and Recommendations ...... 57

References ...... 60

Appendix A: Data Analysis Information ...... 63

A1: Density and Molecular Weight Data ...... 63 A2: List of Symbols ...... 63 A3: Acetamide Flowrate Calculation ...... 65 A4: Acetaldehyde Calculations ...... 66

A5: Acetic Acid Calculations ...... 67 A6: Acetamide Calculations ...... 68 A7: Error Calculations/Propagation ...... 69 Appendix B: Gas Chromatography Information...... 73

B1: Gas Chromatography Instrument Method ...... 73 B2: Calibration Curves ...... 74 B3: Calibration Injections ...... 77 Appendix C: Photos and Diagrams ...... 100

LIST OF TABLES

Page

Table 1: Test Matrix...... 27

Table 2: Schedule of experiments ...... 29

Table 3: Acetic acid steady state effluent mole fractions ...... 38

Table 4: Acetic acid effluent flow rate, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate ...... 38

Table 5: Inconel 625 nominal composition ...... 40

Table 6: Haynes 282 nominal composition ...... 41

Table 7: Acetaldehyde steady state effluent mole fractions ...... 47

Table 8: Acetaldehyde steady state effluent flow rate, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate ...... 47

Table 9: Acetamide steady state effluent mole fractions ...... 53

Table 10: Acetamide steady state effluent flow rate, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate ...... 53

Table A1: Density and molar mass of gases that constitute syngas ...... 63

Table A2: Density and molar mass of chemical feedstocks utilized ...... 63

Table A3: Slopes, intercepts, and their errors for the GC calibration curves ...... 69

Table B1: Standard gases used for calibration (Note: Gas 7 also had 15.1% butylene and

15.0% propylene and was only used to calibrate ethylene) ...... 78

LIST OF FIGURES

Page

Figure 1: Phase diagram for water ...... 13

Figure 2: Density of water as a function of temperature ...... 14

Figure 3: Dielectric constant for water ...... 15

Figure 4: Process flow diagram of the supercritical water gasification unit...... 24

Figure 5: Run ID 5 (acetic acid number 1) steady state gas chromatogram ...... 33

Figure 6: Run ID 6 (acetic acid number 2) steady state gas chromatogram ...... 34

Figure 7: Run ID 4 (acetic acid number 3) steady state gas chromatogram ...... 35

Figure 8: Run ID 11 (acetic acid number 4) steady state gas chromatogram ...... 36

Figure 9: Run ID 13 (acetic acid number 5) steady state gas chromatogram ...... 37

Figure 10: Run ID 2 (acetaldehyde number 1) steady state gas chromatogram ...... 44

Figure 11: Run ID 1 (acetaldehyde number 2) steady state gas chromatogram ...... 45

Figure 12: Run ID 10 (acetaldehyde number 3) steady state gas chromatogram ...... 46

Figure 13: Run ID 9 (acetamide number 1) steady state gas chromatogram ...... 50

Figure 14: Run ID 8 (acetamide number 2) steady state gas chromatogram ...... 51

Figure 15: Run ID 12 (acetamide number 3) steady state gas chromatogram ...... 52

Figure B1: Hydrogen calibration curve ...... 74

Figure B2: Carbon monoxide calibration curve...... 75

Figure B3: Carbon dioxide calibration curve...... 75

Figure B4: Methane calibration curve ...... 76

Figure B5: Ethane calibration curve ...... 76

Figure B6: Ethylene calibration curve ...... 77

Figure B7: Calibration Gas Number 1 injection number 1 ...... 79

Figure B8: Calibration Gas Number 1 injection number 2 ...... 80

Figure B9: Calibration Gas Number 1 injection number 3 ...... 81

Figure B10: Calibration Gas Number 2 injection number 1 ...... 82

Figure B11: Calibration Gas Number 2 injection number 2 ...... 83

Figure B12: Calibration Gas Number 2 injection number 3 ...... 84

Figure B13: Calibration Gas Number 3 injection number 1 ...... 85

Figure B14: Calibration Gas Number 3 injection number 2 ...... 86

Figure B15: Calibration Gas Number 3 injection number 3 ...... 87

Figure B16: Calibration Gas Number 4 injection number 1 ...... 88

Figure B17: Calibration Gas Number 4 injection number 2 ...... 89

Figure B18: Calibration Gas Number 4 injection number 3 ...... 90

Figure B19: Calibration Gas Number 5 injection number 1 ...... 91

Figure B20: Calibration Gas Number 5 injection number 2 ...... 92

Figure B21: Calibration Gas Number 5 injection number 3 ...... 93

Figure B22: Calibration Gas Number 6 injection number 1 ...... 94

Figure B23: Calibration Gas Number 6 injection number 2 ...... 95

Figure B24: Calibration Gas Number 6 injection number 3 ...... 96

Figure B25: Calibration Gas Number 7 injection number 1 ...... 97

Figure B26: Calibration Gas Number 7 injection number 2 ...... 98

Figure B27: Calibration Gas Number 7 injection number ...... 99

Figure C1: Custom built reactor unit (gray box on the right is the reactor and white cylinder on the left is the water preheater) ...... 101

Figure C2: Angled view of the reactor ...... 102

Figure C3: Front view of reactor unit including gas sampling port (top left), liquid product drain (bottom right), and valves for feeding and emptying reactor ...... 103

Figure C4: Close-up view of gas sampling portion of the reactor with a gas sampling port

(red arrow) and thermocouple ...... 104

Figure C5: Close-up view of valve system ...... 105

Figure C6: LabVIEW control system interface ...... 106

Figure C7: Temperature and pressure control portion of LabVIEW interface ...... 107

Figure C8: Temperature and pressure monitoring portion of the LabVIEW interface .108

Figure C9: Gas monitoring section and integrated PFD of the LabVIEW interface ....109

Figure C10: Solid gathered from filters ...... 110

CHAPTER 1: INTRODUCTION

As populations around the world continue to increase, there is an ever-growing demand for different forms of energy supplies. Conventional energy sources such as coal, oil, and gas remain the dominant means of energy production today. However, the continuous consumption of these fossil fuels cannot continue in perpetuity as these nonrenewable sources of energy are not permanently abundant. Other means of energy production, including nuclear energy, wind energy, solar energy, and various biofuels, have been gaining attention as alternative sources of energy. One such alternative that has been investigated is synthesis gas, also known as syngas, created from the supercritical water gasification of various biomass or waste products. Syngas is a blend of mostly hydrogen, carbon dioxide, and carbon monoxide, with other small chain hydrocarbons such as methane and ethane present in smaller quantities.

Syngas has many uses including as a starting material for such chemicals as methanol and dimethyl ether (DME) and as a transportation fuel. Production of syngas is performed via the gasification or pyrolysis of carbon containing materials such as biomass, coal, or wastes.1 One such method of gasification for syngas production is with the use of supercritical water.

Supercritical water (SCW) occurs when water is elevated to pressures and temperatures above its critical point, 374 °C (705 °F) and 22.064 MPa (3200 psia).2 A phase diagram for pure water can be seen in Figure 1.

Figure 1. Phase diagram for water3

Supercritical water, like any supercritical fluid, is neither a liquid nor a gas but can act similarly to either a gas or a liquid depending on the conditions of the water. The density of supercritical water is highly pressure and temperature dependent and is generally much lower than liquid water, but still liquid-like enough to maintain its ability towards solvency. Because of supercritical water’s density dependency on pressure and temperature, the material is very highly tunable to meet the needs of the process in question. The viscosity, generally, is very gaseous in nature which leads the supercritical water medium to have exceptional mass transfer characteristics.4 The density of water as a function of temperature can be seen in Figure 2.

Figure 2. Density of water as a function of temperature3

As shown in Figure 3, water has a relatively high dielectric constant around its boiling point and a value of about 78 at ambient conditions, which leads to water behaving as a very good polar solvent. As the temperature approaches supercritical conditions for water, the dielectric constant decreases continuously and then drastically decreases to a value of around 5 once water becomes a supercritical fluid.5 This leads to water behaving like a poor polar solvent and thus a good solvent for most hydrocarbons due to high miscibility with organics.4 This miscibility eliminates phase boundaries in the water, allowing SCW to act as a good medium for homogeneous reactions.6

Figure 3. Dielectric constant for water3

The ion product (Kw) of water plays an important role in determining which types of chemical reactions occur in the medium. Near the critical temperature of water, the ion product is about 3 times higher than that of ambient liquid water.7 Because of this, there are higher concentrations of H+ and OH- in high temperature water (HTW) and supercritical water, and thus, dense SCW is a great medium for acid or base catalyzed reactions. However, the ion product for gas like density SCW (<0.1g/cm3) is many orders of magnitude lower than that of ambient water, and because of this, free-radical chemistry dictates the chemical reactions that occur in higher temperature SCW.7

Other methods of gasification for biomass include steam gasification and partial oxidation. Supercritical water gasification (SCWG), however, offers significant advantages over these other gasification methods. Because the supercritical water acts as a solvent, catalyst, and reactant in SCWG, the biomass does not need to be dried before

gasification, an energy intensive and costly process, and can be pumped into the reactor as a wet reactant.8 Supercritical water gasification also offers smaller reactor sizes and faster reaction times without the need of a catalyst as compared to other gasification methods. As mentioned earlier, phase boundaries do not occur in SCW. Other methods of gasification do not possess this benefit and can be limited by mass transfer as the reactions occur at the gas-solid phase boundary. Using steam reformation for biomass gasification leads to high amounts of tar and char formation in the reactor with low hydrogen yields.4,9,10 Supercritical water gasification can be utilized with many biomass feedstocks including switchgrass8, algae11, corn-starch gels12, potato-starch gels12, wood sawdust12,13, and potato wastes12.

The area in which biomass energy sources, including plant matter and organic waste, are similar to each other is through the presence of oxygenated hydrocarbons, including carboxylic acids, aldehydes, ketones, and amides among others, in the biomass.

This study will focus on a comparative study of the gasification of smaller chain oxygenated hydrocarbons; specifically a carboxylic acid, an aldehyde, and an amide. To model the gasification of these hydrocarbons, the following reactions are utilized.14

푦 퐶 퐻 푂 + (푥 − 푧)퐻 푂 → 푥 퐶푂 + (푥 − 푧 + ) 퐻 (1) 푥 푦 푧 2 2 2

푦 퐶 퐻 푂 + (2푥 − 푧)퐻 푂 → 푥 퐶푂 + (2푥 − 푧 + ) 퐻 (2) 푥 푦 푧 2 2 2 2 or in a more general overall reaction to account for the reactions occurring simultaneously:

푛 퐶푥퐻푦푂푧 + 푚 퐻2푂 → 푎 퐶푂 + 푏 퐶푂2 + 푐 퐻2 (3)

Reaction 3 shows an arbitrary hydrocarbon reacting with water to form carbon monoxide, carbon dioxide, and hydrogen gas. Another important reaction that occurs in

SCWG is the water-gas shift (WGS) reaction (Reaction 4), which is favored in the forward direction at lower temperatures.15

퐶푂 + 퐻2푂 ↔ 퐶푂2 + 퐻2 (4)

The WGS reaction can account for high amounts of hydrogen and carbon dioxide in the product stream of SCWG depending upon the state of the equilibrium. Methane can be formed from the pyrolytic breakup of higher chain hydrocarbons at high temperatures. The water gas shift reaction and pyrolytic breakup change the relative amounts of each gas species after they are formed.14 As stated earlier, supercritical water can catalyze many reactions that are normally acid or base catalyzed. This should apply to the acid catalyzed hydrolysis of amides, as seen below in Reaction 5.

푅퐶푂푁퐻2 + 퐻2푂 → 푅퐶푂푂퐻 + 푁퐻3 (5)

The carboxylic acid formed in Reaction 5 should then undergo further gasification via Reaction 3 to form syngas with some ammonia.

These reactions indicate the complete conversion of the starting material into the syngas constituents. Other intermediates can be formed including formaldehyde and ethylene, and other unknown reaction pathways can occur other than the previously listed reactions.

CHAPTER 2: LITERATURE REVIEW

Supercritical water gasification is a relatively well-known process. Much research has been performed studying the pathways and efficiencies of the SCWG of various starting materials including glucose (a model compound for cellulose), indole, and glucose/phenol mixtures.16–18 Studies have been performed to determine the efficacy of catalysts used during gasification to try and improve the gasification process.8,19–21 Other investigations have shown that the gasification of various starting materials yields many different intermediates and side products including aldehydes, organic acids, ketones, and furfurals.22–24

There have, however, been limited studies on the individual oxygenated hydrocarbons mentioned previously, their effects on the gasification process itself, and the reaction mechanisms of the gasification process of these hydrocarbons. One such study examined the effects of chain length on the gasification of alcohols and organic acids while varying the chain length from one carbon to eight carbons.25 It was determined that alcohols were much easier to gasify than carboxylic acids in general while alcohols higher than C3 were also difficult to gasify due to coke formation. The initial concentration of carboxylic acids had a great effect on the gasification efficiency

(GE) but no such effect was found in the alcohols. It was also found that increasing the chain length increased the yields of methane and ethane, while the hydrogen yield remained mostly steady after C3. Also, it was determined that the GE for acids was highest for C1 acids and decreases whereas GE for alcohols increased from C1 to C2 and then decreased after that. Both, however, stabilized around 50% at the chosen conditions.

Gasification efficiency was shown to have a strong correlation with the C/O and C/OH ratios.

Another study investigated the conversion of three different C4 compounds (1- butanol, 1-butanal, and cis-butanediol).26 This study involved compounds that each carry different functional groups (alcohol, aldehyde, and multiple alcohols respectively) that are found in intermediates of SCWG. It was determined that the formation of aromatic rings was not dependent upon the starting functional group as all three of the starting materials formed aromatic rings. Also, the starting materials underwent typical reactions for the particular functional group with the aldehyde undergoing an aldol condensation reaction and the diol reacting to form a cyclic ether.

Previous researchers at Ohio University’s Sustainable Energy and Advanced

Materials (SEAM) Laboratory studied the gasification of acetaldehyde and formaldehyde, as they are intermediate compounds produced during the gasification of cellulose and glycerin with many people believing that aldehydes are the last intermediates in the gasification process.27 It was determined that both reactants undergo a variety of different reactions that form a variety of different products and are in fact not the last intermediates in the gasification process. The compounds formed were also able to react to form other gaseous products, and some intermediates formed were in fact precursors to coke/tar.

The research done has shown that supercritical water is a good medium for various reactions including the gasification of biomass feeds into usable gases. The supercritical gasification of various biomass feedstocks has been studied. However, there

are very few studies on the individual oxygenated hydrocarbon functional groups that constitute this biomass. This study will focus on the individual gasification of three different two-carbon oxygenated hydrocarbons that are all carboxylic acid derivatives, specifically acetic acid, acetamide, and acetaldehyde, to determine the effects that the groups themselves have on the gasification process and the method by which the gasification process proceeds on the hydrocarbons themselves.

CHAPTER 3: SIGNIFICANCE AND OBJECTIVES

This experimental work could have a far reaching impact on the energy security of the United States in particular and of the world in general. With better understanding of the supercritical water gasification process at a more concentrated level, better SCWG processes can be developed that increase the yield and conversion of waste or biomass into usable fuel. This better understanding at a lab scale level can be used to scale-up the technology to create power plants that utilize SCWG as a means to produce usable fuels and decrease the reliance on foreign sources of nonrenewable fuels. Also, SCWG can be used as a means for treating both industrial and municipal waste water. This could lead to more and better water treatment facilities and better water treatment at chemical plants if integrated SCWG processes are added into industrial water treatment practices.

Currently, there are commercial water treatment plants that incorporate a wet oxidation process similar to SCWG that is a high temperature water (HTW) process, but nothing in terms of supercritical water is used in that capacity.

The objective of this thesis work was to determine the following for each chemical feedstock gasified:

1.1. Syngas composition

1.2. Hydrogen Yield (moles of hydrogen gas formed versus the moles of feedstock

fed to the reactor)

1.3. Gasification Rate (rate at which the gaseous effluent is produced)

1.4. Gasification Efficiency (gaseous effluent mass flow rate divided by the fuel feed

mass flow rate)

1.5. Carbon Efficiency (a green chemistry metric that relates the total amount of

carbon in the product to the total amount of carbon in the feed)

Each reactant feedstock studied was a derivative of acetic acid with the form of:

H3C X where the X is a substituted group as follows: 1) OH for acetic acid 2) NH2 for acetamide 3) H for acetaldehyde

Conclusions were drawn as to the effect that each of the substituted X groups plays on the gasification process in general.

CHAPTER 4: EXPERIMENTAL METHODOLOGY

Section 1: Experimental Apparatus and Chemical Feedstocks

The experiments conducted were run on a custom designed continuous flow reactor that was previously built by past researchers at both the SEAM Lab and the

Transportation Fuels and Polymer Processing Laboratory of Missouri University of

Science and Technology. The reactor system consisted of Chromtech HPLC pumps for the fuel and water feeds (a Prep 36 Dual Piston Pump for the water and an LS-Class High

Pressure Piston Pump for the fuel feed), an Inconel 625/316 stainless steel integrated heat exchanger that cools the reactor effluent while preheating the water, a Watlow band heater for further preheating of the water, a high nickel alloy tubular reactor consisting of a Haynes 282 outer tube and Inconel 625 (Grade II) inner tube, another 316 stainless steel water cooled heat exchanger to further cool the reactor effluent, a liquid and vapor separation system, a gas sampling system that included a Ritter type TG3/3-ER wet test meter to measure the gas volumetric flow rate, and a liquid sampling system. A process flow diagram (PFD) can be seen in Figure 4 and pictures of the reactor unit itself can be seen in Appendix C.

The reactor itself was a 101 mL internal volume annular reactor consisting of a

0.5” inner diameter Haynes 282 outer wall and a 0.25” outer diameter Inconel 625 inner wall. The high nickel alloys were chosen as they have high strengths and good creep resistances while also having a higher corrosion resistance to the severe conditions of supercritical water than stainless steel. The Inconel inner wall was put in place to act as a

Figure 4. Process flow diagram of the supercritical water gasification unit

thermowell to ensure consistent heating and temperature monitoring throughout the reactor. Inconel has also shown catalytic properties in the gasification reactions towards producing a hydrogen rich syngas.10,28,29

The heads of the reactor, which allow the feeds to flow in the bottom of the reactor and the product to flow out the top, were screwed into the reactor with Graphoil, a flexible graphite, gaskets in place to ensure a proper seal. The reactor body heater that surrounds the Haynes 282 reactor wall was custom made by Watlow Electric

Manufacturing Company. The reactor body heater consisted of four heating zones that provide constant heating of the entire reactor and ensure sufficient heating of the reactor.

The integrated heat exchanger was a counter flow, annular heat exchanger that simultaneously heated the feed water while cooling the hot product stream. The heat exchanger was constructed using 0.5” stainless steel outer tubing surrounding a 0.25” inner tubing made of Inconel 625. The entire heat exchanger was wrapped with Samox™ yarn to provide insulation. The reactor effluent exited the top of the reactor and entered the inner tube of the heat exchanger and flowed to the bottom of the heat exchanger. Its temperature at this point was around 40-80 °C depending upon the temperature inside the reactor. The feed water entered the bottom of the integrated heat exchanger and flowed up the outer tube where it was heated to temperatures around 200-400 °C before entering another preheater. Inconel 625 was used as the inner material as the fluid leaving the effluent was around temperatures of 400 °C. This low temperature supercritical water would cause severe corrosion to stainless steel tubing so a high nickel alloy was needed.30,31 The outer tube, however, could be stainless steel because the water temperature in the outer tubing never reaches temperatures higher than 200 °C so stainless steel tubing (SEAM Lab’s standard tubing) was sufficient.

The second water preheater heated the hot water from the integrated heat exchanger to roughly 600-650 °C for entrance into the reactor. The tubing through which the water flows was Hastelloy C276. A high nickel alloy was needed due to the supercritical conditions of the water once it was in the preheater. The heating elements used were Watlow MI Band Heaters. The Watlow MI band heater derives its name and performance from Watlow’s mineral insulation, a material that has higher thermal conductivity than materials used in conventional heaters. The Watlow MI band heater was fabricated with a thin layer of highly conductive material that separates the wire from the inside covering. A thicker, lower conductive layer surrounds the element wire to guide the heat inward towards the tubing.32

The preheated water and chemical feedstock were pumped into the bottom of the reactor separately to ensure there were no unwanted reactions that could occur at lower temperatures and pressures. During preheating, only water was pumped into the reactor.

However, during initial experimental runs, there was backflow of the water into the fuel feed line which caused severe coking to occur in the tubing. To ensure no coking reactions or other unwanted reactions occurred during this preheating, the operating procedure was modified to flow air through the feed line to ensure there was no backflow of water during preheating. This ensured that water could not enter the fuel feed line and thus coking could not occur. Once preheating was over, the air was turned off and the feed fuel was pumped into the reactor. The entire reactor system was automated and controlled by a custom LabVIEW control system. A screenshot of the LabVIEW monitoring system can be seen in Appendix C.

The hydrocarbons studied were all two-carbon carboxylic acid derivatives. They were acetic acid (an organic acid), acetaldehyde (an aldehyde), and acetamide (an amide).

Each hydrocarbon contained two carbons to ensure no cyclization reactions among the carbons themselves. With such small and consistent chain-length on the hydrocarbons, the direct effects of the functional groups themselves on the gasification process could be studied. The chemical feedstocks were all purchased from Fisher Scientific. Specifically, the chemicals were Acetic Acid, Glacial (CAS: A38-212); Acetaldehyde, 99.5%, extra pure (CAS: 75-07-0); and Acetamide, 99%, pure (CAS: 60-35-5).

Section 2: Experimental Design

Each chemical feedstock was gasified at 650 °C at a residence time of 30 seconds.

The flow rates of the water and the chemical feedstocks to match a residence time of 30 seconds at 650 °C were calculated using ASPEN Plus V8.8 using the Peng-Robinson equation of state with Wong-Sandler mixing rules. The test matrix used for experimentation was as follows:

Table 1. Test Matrix

Run Number Experiment ID Reactant 6 1 1 4 2 1 2 3 1 8 4 2 1 5 2 3 6 2 9 7 3 7 8 3 5 9 3

In the test matrix, Reactant 1 was acetaldehyde, Reactant 2 was acetic acid, and

Reactant 3 was acetamide. The order of experimentation was randomized using Excel.

Table 2 is the actual schedule followed for experimentation.

During experimentation, slight changes were made to the test matrix. First, Run

ID 2 failed because there was an issue with the GC septum leaking so the results obtained could not be quantified. This run was repeated as Run ID 10. Run ID 7 also failed because there was a clog in the pump’s inlet filter that was causing the pressure of the pump to increase drastically and would not allow for the proper flow rate. The filter was cleaned and experiments were continued. Run ID 7 was repeated as Run ID 12. Finally, two additional acetic acid experiments were performed because of inconsistency in results that will be explained later in Chapter 5 Section 1.

During experimentation, water and air were fed to the reactor to preheat the reactor to approximately 650 °C. Once preheating was achieved (approximately 45 minutes to 1 hour), the chemical feedstock pump was powered on and the fuel was fed into the reactor from a nitrogen purged, capped glass container that held the chemical. At this point, the air was turned off to ensure the reactions took place without the presence of oxygen. At this point, the LabVIEW system was monitored for the product gas flow rate and once gas started to be produced, 1 mL samples were taken with a pressure lock gas sampling syringe and injected into the gas chromatograph (GC).

The GC used at the SEAM Lab was a Trace GC Ultra produced by ThermoFisher

Scientific. The column inside the GC was a Restek packed column (part number 19808) with a length of 2 meters, inner diameter of 1 mm, and an outer diameter of 1/16”. To

Table 2. Schedule of experiments

Flow Rates Experimental Run (ml/min) Date Feed Chemical Order ID Water Fuel

6/11/2018 1 5 Acetic Acid 14.75 1.475 Acetaldehyde (Failed 6/12/2018 2 3 15.17 1.517 because of GC error) 6/14/2018 3 6 Acetic Acid 14.75 1.475

6/15/2018 4 2 Acetaldehyde 15.17 1.517

6/18/2018 5 9 Acetamide 14.36 4.32

6/19/2018 6 1 Acetaldehyde 15.17 1.517

6/19/2018 7 8 Acetamide 14.36 4.32

6/20/2018 8 4 Acetic Acid 14.75 1.475 Acetamide 6/20/2018 9 7 14.36 4.32 (run failed) Acetaldehyde 6/21/2018 10 10 (Repeat of 15.17 1.517 Run ID 3) 6/22/2018 11 11 Acetic Acid 14.75 1.475 Acetamide 7/2/2018 12 12 (repeat of Run 14.36 4.32 ID 7) 7/5/2018 13 13 Acetic Acid 14.75 1.475

calibrate the GC for use, gases of known composition were injected three separate times into the GC to obtain elution time windows along with areas corresponding to the amount of each gas injected. The elution time windows were used to determine the identity of the unknown gases in reaction samples that were injected. Linear regressions were performed and the composition to area values were plotted and linear calibration curves were constructed where unknown amounts of a gas were quantified by using the equation of the calibration curve. An overview of the instrument method that was used, along with the calibration curves from the GC, can be seen in Appendix B. The data obtained from the GC was analyzed using the Chromeleon software package.

To end the experiments, steady state needed to be reached. To determine if a steady state had been reached, the composition of consecutive gas samples taken had to have amounts of hydrogen and the other major component that were consistent to values around 5% and the product flowrate measured from the wet test meter had to have no significant change between samples. At this point, steady state had been reached and an experiment was deemed complete. The reactor was shut down at this time by depressurizing the system and turning off the heaters. The fuel feed was shut off and air was once again released into the system to ensure that there was no backflow from the water feed into the fuel feed line. Water and air continued to flow to cool the reactor system until temperatures were deemed safe enough, at which point the water was turned off while the air remained on to completely evacuate the reactor of water.

To prepare the fuel feed system for the next experiment, water was run through the pump into the purge line of the feed system. This water cleaned the lines of the feed

system and ensured the pump was free of the feedstock. The glass container was washed with DI water and dried overnight before being filled with the next day’s experimental feedstock.

CHAPTER 5: RESULTS AND DISCUSSION

All data analysis calculations can be seen in Appendix A. The method used for propagating error from the known values into calculated results is shown in Appendix

A7.

Section 1: Acetic Acid

Acetic acid is the two-carbon equivalent of carboxylic acid with the chemical formula of CH3COOH. Acetic acid was gasified 5 times at 650 °C and 3600 psi with a residence time of 30 seconds with differing results between Runs ID 5 and 6 (the first two acetic acid experiments) and Runs ID 4, 11, and 13 (the final three acetic acid experiments).

The gas chromatograms of each steady state gas injection can be seen in Figures

5-9. The calculated results of the mole fractions of each gaseous component, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate are shown in Tables

3 and 4.

The acetic acid results can be broken up into two groups, the first two runs with a high hydrogen yield, and the last three runs with lower hydrogen yields. The first two experiments had relatively high hydrogen yields (~1.7 mol H2 per mol acetic acid fed) with a composition of approximately 55% H2, 35% CO2, and 10% CH4. These results vary drastically in the second group of experiments. Not only are the compositions significantly different with more gases present in the sample, but also the hydrogen yield is severely depleted to values around 0.023 mol H2 per mol acetic acid fed, or values around 1% of the first two experiments. The drastic change in results was initially

Figure 5. Run ID 5 (acetic acid number 1) steady state gas chromatogram

Figure 6. Run ID 6 (acetic acid number 2) steady state gas chromatogram

Figure 7. Run ID 4 (acetic acid number 3) steady state gas chromatogram

Figure 8. Run ID 11 (acetic acid number 4) steady state gas chromatogram

Figure 9. Run ID 13 (acetic acid number 5) steady state gas chromatogram

Table 3. Acetic acid steady state effluent mole fractions

Acetic Acid

Run H2 Mole CO Mole CO2 Mole CH4 Mole C2H6 Mole C2H4 Mole Date ID Fraction Fraction Fraction Fraction Fraction Fraction 0.511 ± 0.364 ± 0.125 ± 6/11/2018 5 0 0 0 0.045 0.049 0.008 0.560 ± 0.357 ± 0.083 ± 6/14/2018 6 0 0 0 0.047 0.047 0.006 0.048 ± 0.092 ± 0.438 ± 0.412 ± 0.000 ± 0.011 ± 6/20/2018 4 0.052 0.047 0.058 0.035 0.004 0.009 0.056 ± 0.088 ± 0.428 ± 0.418 ± 0.001 ± 0.001 ± 6/22/2018 11 0.051 0.047 0.057 0.035 0.004 0.009 0.046 ± 0.092 ± 0.436 ± 0.416 ± 0.000 ± 0.010 ± 7/5/2018 13 0.052 0.046 0.058 0.035 0.004 0.009

Table 4. Acetic acid effluent flow rate, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate

Acetic Acid Effluent Gasification Carbon Gasification Run Yield Date Flow Rate Efficiency Efficiency Rate ID (mol/mol) (mL/min) (%) (%) (g/mL*min) 1.770 ± 6/11/2018 5 2185 ± 5 110.0 ± 7.4 84.7 ± 15.0 0.231 ± 0.015 0.197 1.698 ± 6/14/2018 6 1911 ± 5 91.6 ± 6.1 66.6 ± 11.8 0.192 ± 0.013 0.183 0.021 ± 6/20/2018 4 278 ± 5 23.2 ± 2.3 21.2 ± 32.8 0.049 ± 0.005 0.023 0.025 ± 6/22/2018 11 284 ± 5 23.3 ± 2.3 21.5 ± 30.9 0.049 ± 0.005 0.023 0.022 ± 7/5/2018 13 294 ± 5 24.5 ± 2.4 22.5 ± 34.8 0.052 ± 0.005 0.024

postulated to be caused by a breakdown of the acetic acid. Fresh acetic acid was ordered between Run ID 11 and Run ID 13, and as seen above, the results were similar to the results obtained for Runs ID 4 and 11. This confirmed that the acetic acid breaking down

39 is not what contributed to the change in results as there was no chance for acetic acid breakdown with the fresh acid.

Gutiérrez Ortiz et al. ran experiments on acetic acid at temperatures of 700 °C and pressures of 240 bar (~3500 psi) with residences times ranging from 17s to 21s in a tubular Inconel 625 reactor.33 Although not run at the exact same conditions, the reaction conditions were similar enough for comparison. The results obtained at 10 wt% (closest to the concentration used in this experimentation) showed a comparable composition, yield, and gasification efficiency. The gas Gutiérrez Ortiz et al. obtained consisted of

5.1% H2, 48.8% CO2, 41.7% CH4, and 4.3% CO with a yield of 0.09 mol H2 per mol acetic acid fed and a gasification efficiency of 90.3%. Chakinala et al. also achieved similar results while gasifying a 10 wt% acetic acid solution at 600 °C and ~3600 psi.25

The similarity between these works and the last three experimental runs provides validity to those experiments.

The low hydrogen composition, as well as the relatively high and almost equal

CO2 and CH4 mole fractions, can be explained in potentially three ways: by the Sabatier reaction34, by hydrogen abstraction from the carboxyl group25, or by the conversion of acetic acid into acetone followed by subsequent decomposition into ethylene and cracking into methane33.

The Sabatier reaction occurs as follows:

푘퐽 퐶푂 + 4퐻 ↔ 퐶퐻 + 2퐻 푂 Δ퐻표 = −164.9 (6) 2 2 4 2 푅 푚표푙

The Sabatier reaction converts carbon dioxide and hydrogen into methane and water and is utilized by NASA to recover water from CO2 produced via astronaut

40 respiration and the residual H2 from the hydrolysis of the water that supplies the oxygen.35 The Sabatier reaction would account for the high amounts of methane and low amount of hydrogen in the effluent gas, as well as the overall lower amounts of gas produced as the water produced is condensed and is part of the bulk reaction medium and not accounted for in the material balance.

Nickel catalysts are generally considered to be the traditional Sabatier reaction catalyst.35 There have been many studies that attempted to elucidate the efficacy of various nickel catalysts, including a Ni-Al2O3 catalyst, various NiAl(O)x catalysts, and a

36–38 Ni/SiO2 catalyst. More recent studies have focused on support and promoter improvement for nickel catalysts.39 As mentioned before, the reactor materials utilized in the SEAM Lab’s multifuel reformation reactor are Inconel 625 and Haynes 282, both of which are high-nickel alloys. The composition of each alloy is shown in Tables 5 and 6 respectively.

Table 5. Inconel 625 nominal composition40

Component Weight % Nickel 58.0 min Chromium 20.0 - 23.0 Iron 5.0 max Molybdenum 8.0 – 10.0 Niobium (plus 3.15 – 4.15 Tantalum) Carbon 0.10 max Manganese 0.50 max Silicon 0.50 max Phosphorous 0.015 max Sulfur 0.015 max Aluminum 0.40 max Titanium 0.40 max Cobalt 1.0 max

Table 6. Haynes 282 nominal composition41

Component Weight % Nickel 57 (balance) Chromium 20 Cobalt 10 Molybdenum 8.5 Titanium 2.1 Aluminum 1.5 Iron 1.5 max Manganese 0.3 max Silicon 0.15 max Carbon 0.06 Boron 0.005

Not only are both alloys high in nickel content, but also have the presence of previously mentioned proven catalytic materials that can enhance the efficacy of these nickel catalysts such as silicon and aluminum. The Sabatier reaction, a reversible reaction, is also favored in the forward direction at higher pressures due to the imbalance in moles of gaseous species (5 moles to 3 moles). This forces the equilibrium to the side of producing more methane and water. The presence of carbon monoxide in the products is due to a shift in the water gas shift reaction that is favored in the direction of producing carbon monoxide at higher temperatures.41

Another possible explanation for the relatively low amounts of hydrogen and higher and almost equimolar amounts of methane and carbon dioxide could be the decarboxylation of the acetic acid into methane and carbon dioxide (Reaction 7).

퐻3퐶 − 퐶푂푂퐻 ↔ 퐶퐻4 + 퐶푂2 (7)

Kharaka et. al showed that the decarboxylation of acetic acid into methane and carbon dioxide has a relatively low activation energy and relatively high reaction rates with an increasing reaction rate as temperature increases.42 This shows that the decarboxylation reaction is favored in the forward direction as temperatures increase and should readily occur at the temperatures utilized in this experimentation. Verma and

Kishore also verified this using a density functional theory approach.43

This decarboxylation, however, does not account for the carbon monoxide present. Another side reaction is needed to produce this carbon monoxide, and a shift in the WGS equilibrium could account for the slightly higher amounts of carbon dioxide than methane as well as the presence of hydrogen gas in the effluent.

Finally, the third method that could account for the results seen are a series of reactions including the formation of acetone from acetic acid (Reaction 8), the decomposition of acetone into ethylene (Reaction 9), and the cracking of ethylene into carbon and hydrogen, which form methane (Reaction 10).

2퐻3퐶 − 퐶푂푂퐻 ↔ 퐻3퐶 − 퐶푂 − 퐶퐻3 + 퐶푂2 + 퐻2푂 (8)

퐻3퐶 − 퐶푂 − 퐶퐻3 ↔ 퐶2퐻4 + 퐶푂 + 퐻2 (9)

퐶2퐻4 → 2퐶(푠) + 2퐻2 → 퐶(푠) + 퐶퐻4 (10)

This leads to an overall reaction (Reaction 11) that produces an equimolar mixture of gases consisting of carbon dioxide, carbon monoxide, hydrogen gas, and methane with water and solid carbon also present.

2퐻3퐶 − 퐶푂푂퐻 ↔ 퐶푂2 + 퐻2푂 + 퐶푂 + 퐻2 + 퐶퐻4 + 퐶(푠) (11)

A shift in the water gas shift reaction equilibrium along with the subsequent

Sabatier reaction would then stoichiometrically account for the decrease in hydrogen and carbon monoxide and the increase in the composition of carbon dioxide and methane.

Solid carbon, in the form of coke, would also be a product of Reaction 10. While solids identification is not a part of the scope of this work, filters placed downstream of the reactor were taken off at the end of experimentation and a black, charcoal like solid was present (seen in Figure C10). Pathway 3 could describe this coke formation, but general hydrocarbon decomposition can also account for the formation of solids and could be present in any of the three suggested pathways.

Section 2: Acetaldehyde

Acetaldehyde is a two-carbon aldehyde with the chemical formula of C2H4O. The hydrogen attached to the carbonyl carbon is readily available for gasification with water to form the H2 in the syngas. Acetaldehyde was gasified 3 times at 650 °C and 3600 psi with a residence time of 30 seconds with relatively consistent results.

The gas chromatograms of each steady state gas injection can be seen in Figures

10-12. The calculated results of mole fraction, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate are shown in Tables 7 and 8.

The results obtained from acetaldehyde gasification are relatively repeatable with a slight difference between Run ID 2 and Runs ID 1 and 10. Run ID 2 had a composition of around 52% H2, 30% CO2, and 18% CH4. The final two acetaldehyde experiments had compositions of around 40% H2, 8% CO, 27% CO2, and 25% CH4. This slight difference will be postulated in Chapter 5 Section 4.

Figure 10. Run ID 2 (acetaldehyde number 1) steady state gas chromatogram

Figure 11. Run ID 1 (acetaldehyde number 2) steady state gas chromatogram

Figure 12. Run ID 10 (acetaldehyde number 3) steady state gas chromatogram

Table 7. Acetaldehyde steady state effluent mole fractions

Acetaldehyde

CO CO2 CH4 C2H6 C2H4 Run H2 Mole Date Mole Mole Mole Mole Mole ID Fraction Fraction Fraction Fraction Fraction Fraction 0.515 ± 0.304 ± 0.180 ± 0.002 ± 6/15/2018 2 0 0 0.046 0.047 0.011 0.004 0.399 ± 0.081 ± 0.279 ± 0.238 ± 0.003 ± 6/19/2018 1 0 0.045 0.049 0.048 0.018 0.004 0.393 ± 0.086 ± 0.266 ± 0.251 ± 0.003 ± 6/21/2018 10 0 0.046 0.049 0.048 0.019 0.004

Table 8. Acetaldehyde steady state effluent flow rate, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate Acetaldehyde Effluent Gasification Carbon Gasification Run Yield Date Flow Rate Efficiency Efficiency Rate ID (mol/mol) (mL/min) (%) (%) (g/mL*min) 1.693 ± 6/15/2018 2 2183 ± 5 129.5 ± 8.6 80.1 ± 15.6 0.204 ± 0.014 0.188 1.094 ± 6/19/2018 1 1820 ± 5 135.6 ± 11.4 82.8 ± 18.7 0.214 ± 0.018 0.154 1.077 ± 6/21/2018 10 1819 ± 5 135.2 ± 11.4 83.6 ± 29.7 0.213 ± 0.018 0.155

Overall, the acetaldehyde results show a more promising gasification than that of acetic acid. The hydrogen yields range from 1.1 to 1.7 moles H2 per mole acetaldehyde fed with gaseous effluent flow rates ranging from 1.8 to 2.2 L/min and gasification efficiencies around 130%. This more efficient gasification was performed previously at the SEAM Lab by Tschannen et al. in their study of acetaldehyde and formaldehyde with relatively similar results.27 The results showed a gaseous composition of approximately

28% H2, 9% CO, 28% CO2, 29% CH4, and 4% C2H6 with gaseous effluent flow rates of

3.9 L/min. These experiments were run on a similar reactor setup with a tubular Haynes

282 reactor of 0.1 L internal volume. The difference in these results could be due to a monolithic catalytic effect between the two reactor surfaces that is only present due to the annular nature of the reactor used in this experimentation as opposed to the tubular nature of the previous work.

Tschannen et al. showed that at higher temperatures (ranging from 600°C to

700°C), the main reaction occurring was the decomposition of acetaldehyde into methane and carbon monoxide. Other side reactions were shown to be carbon monoxide producing, which could account for the higher amounts of carbon monoxide without producing extra methane. This higher amount of carbon monoxide would then shift the water gas shift equilibrium towards producing hydrogen and carbon dioxide, which account for the higher amounts of both than if acetaldehyde strictly breaks down into methane and carbon monoxide.

Another proposed mechanism for hydrogen production that was not the water gas shift reaction was the reacting and dehydrating of intermediates into aromatics that produced hydrogen gas. Analysis on the liquid byproduct, which was outside the scope of this work, would need to be performed to determine if aromatics were present to verify this claim and determine if this is a reaction pathway in acetaldehyde gasification.

A third, and related, pathway presented by Tschannen et al. was the reaction of acetaldehyde with itself to form acetone, hydrogen gas, and carbon monoxide. This, along with the previously stated breakdown of acetone (Reaction 9 and Reaction 10),

49 would also account for the higher amount of hydrogen than predicted solely from the breakdown of acetaldehyde. These reactions also equally produce carbon monoxide and hydrogen so they should not shift the water gas shift equilibrium and thus this accounts for the amount of carbon dioxide present.

Section 3: Acetamide

Acetamide is a two-carbon amide with the chemical formula of C2H5NO. There are no readily available hydrogen atoms for gasification with water to form the H2 in the syngas as the hydrogen attached to the NH2 group is not readily available for supercritical water reactions. Acetamide was gasified 3 times at 650 °C and 3600 psi with a residence time of 30 seconds with a high repeatability.

The gas chromatograms of each steady state gas injection can be seen in Figures

13-15. The calculated results of mole fraction, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate are shown in Tables 9 and 10.

Acetamide gasification is a mostly unknown process as there are limited studies specifically on nitrogen containing hydrocarbons and most studies that do focus on nitrogen containing hydrocarbons do not focus on the gasification of small chain, nitrogen containing hydrocarbons, but rather larger nitrogen containing molecules such as indole.16 Because of this, verifying results obtained is not feasible, but the results obtained were repeatable, which lends a degree of authority to the findings.

The composition of the acetamide gaseous effluent is approximately 13% H2,

11% CO, 6% CO2, 69% CH4, and 1% C2H4 with a yield of about 0.027 moles of H2 produced per mole of acetamide fed. Studies have shown that in supercritical water,

Figure 13. Run ID 9 (acetamide number 1) steady state gas chromatogram

Figure 14. Run ID 8 (acetamide number 2) steady state gas chromatogram

Figure 15. Run ID 12 (acetamide number 3) steady state gas chromatogram

Table 9. Acetamide steady state effluent mole fractions Acetamide

CO CO2 CH4 C2H6 C2H4 Run H2 Mole Date Mole Mole Mole Mole Mole ID Fraction Fraction Fraction Fraction Fraction Fraction 0.123 ± 0.112 ± 0.065 ± 0.691 ± 0.009 ± 6/18/2018 9 0 0.050 0.047 0.054 0.061 0.009 0.155 ± 0.093 ± 0.051 ± 0.691 ± 0.001 ± 0.010 ± 6/19/2018 8 0.049 0.049 0.055 0.062 0.004 0.009 0.110 ± 0.123 ± 0.060 ± 0.698 ± 0.010 ± 7/2/2018 12 0 0.052 0.047 0.055 0.063 0.009

Table 10. Acetamide steady state effluent flow rate, hydrogen yield, gasification efficiency, carbon efficiency, and gasification rate Acetamide Effluent Carbon Gasification Run Yield Gasification Date Flow Rate Efficiency Rate ID (mol/mol) Efficiency (%) (mL/min) (%) (g/ml*min) 0.031 ± 11.1 ± 6/18/2018 9 205 ± 5 9.0 ± 1.0 0.021 ± 0.002 0.013 11.6 0.028 ± 6/19/2018 8 145 ± 5 5.8 ± 0.7 7.6 ± 9.9 0.014 ± 0.002 0.009 0.021 ± 7/2/2018 12 155 ± 5 6.9 ± 0.8 8.6 ± 10.2 0.016 ± 0.002 0.010

nitriles hydrolyze into amides which further hydrolyze into the corresponding acid.44–46

The hydrolysis of acetamide into acetic acid and subsequent gasification of acetic acid should produce similar results to the acetic acid gasification. In terms of hydrogen yield and effluent flow rate, this is the case. However, the acetamide gasification produces a gas that has significantly higher methane and hydrogen mole fractions and a significantly lower carbon dioxide mole fraction.

If acetamide is hydrolyzed into acetic acid and then gasified and the Sabatier reaction occurs, the continued hydrolysis of acetic acid would remove water from the

54 system and shift the Sabatier reaction towards the right. This would account for the increase in the percentage of methane and hydrogen and the decrease in carbon dioxide.

However, this does not account for the similar hydrogen yield as shifting the Sabatier reaction to the right should greatly diminish the amount of hydrogen present. The hydrogen yield, however, stays roughly the same.

However, the hydrolysis of acetamide into acetic acid produces ammonia that is not present in the gaseous effluent so it must be dissolved in the liquid effluent, though verification through liquid testing would prove this. Also, considering ammonia’s very high solubility in water, this is very likely.47 This ammonia, once the acetic acid is reacted away, raises the pH of the resulting water after depressurization and cooling. As pH values increase with the increase in dissolved ammonia, carbon dioxide more easily dissolves in water to balance the equilibria of carbonic acid formation. This removal of carbon dioxide from the gas stream would account for the low mole fraction of carbon dioxide compared to the acetic acid gasification. Also, removal of the carbon dioxide shifts both the water gas shift and Sabatier equilibriums towards producing more hydrogen. A balance between these equilibria causes the yield of hydrogen to be about the same as that of acetic acid while also removing the carbon dioxide from the gaseous stream.

Section 4: Connecting Trends

In regards to producing a syngas with a high hydrogen yield and high volumetric flow rate, acetaldehyde has a significantly higher yield and flow rate than that of acetic

55 acid or acetamide. By utilizing a t-test analysis, acetic acid and acetamide do not have statistically different yields and acetic acid has only a slightly higher flow rate.

In terms of carbonyl reactivity towards nucleophiles (electron pair donating species in a chemical reaction), aldehydes are the most reactive, followed by carboxylic acids and then closely followed by amides.48 This trend of carbonyl reactivity towards nucleophiles follows the same trend as the reactivity of the carboxylic acid derivatives towards supercritical water gasification. Water itself is generally a poor nucleophile unless catalyzed by an acid catalyst.48 As previously stated, supercritical water can catalyze reactions that are generally catalyzed by acids or bases. This leads to the hypothesis that supercritical water catalyzes the nucleophilic attack of water towards carbonyl groups, and the supercritical water gasification process itself proceeds via a nucleophilic attack mechanism. Because of this, it is reasonable that the reactivity of these groups in supercritical water follows the same trend as general nucleophilic reactivity of carbonyls. Verifying this trend could be accomplished by gasifying other similar carbonyls such as acid anhydrides and ketones and determining if these carbonyl groups fit into this trend.

Official reactions run before June 18, 2018 (Runs ID 5, 6, and 2), as well as initial experiments on methanol, produced syngas blends that had no carbon monoxide present.

Reactions after this point, however, all produced syngas that was roughly 8 to 12 percent carbon monoxide. This drastic shift from having no carbon monoxide present to almost

10% regardless of the feedstock used indicates a change in the reactor or reaction process itself. This change is most likely due to a corrosion product layer forming on either the

56 inner Inconel wall or the outer Haynes 282 wall. This could either be through the formation of a layer that hinders the catalytic effects of the high nickel alloys or the destruction of a layer that was already present beforehand.

A corrosion product layer in the form of a nickel oxide forms on Inconel 625 in supercritical water.49 This oxide layer could act as a hindrance, when compared to the

Inconel 625 itself, towards the forward direction of the water gas shift reaction and thus account for the presence of carbon monoxide that was not present in initial experiments.

Haynes 282 is a relatively new materials, and thus, there are few studies in regards to the material. Because of this, there is virtually nothing known about the catalytic effects of the alloy. However, being a high nickel alloy like Inconel 625, as well as being composed of other catalytic elements such as chromium, cobalt, and molybdenum, should lend Haynes 282 towards having catalytic effects similar to those of

Inconel 625 (Grade I). Further experimentation into the development of corrosion product layers on both of the high nickel alloys is needed to elucidate the catalytic effects of these layers as well as experimentation to determine the catalytic efficacy of bare Haynes 282 itself towards supercritical water reactions.

The presence of a corrosion product layer also explains the previously mentioned difference observed between the first two acetic acid experiments and the final three. A product layer on the Haynes 282 could hinder any catalytic effect the nickel alloy could possess toward acetic acid gasification. Because there is limited knowledge of the gasification process with Haynes 282 as a reactor material, verification of the first two experiments is impossible.

CHAPTER 6: CONCLUSIONS AND RECOMMENDATIONS

Three different two-carbon carboxylic acid derivatives were gasified at 650 °C and 3600 psi with a residence time of 30 seconds. The three carboxylic acid derivatives were acetic acid, acetaldehyde, and acetamide. Acetaldehyde underwent the best gasification in terms of hydrogen yield (~1.1 moles of hydrogen formed per mole of acetaldehyde fed) and gaseous effluent flow rate (~2.0 L/min). Acetic acid gasification and acetamide gasification did not produce nearly as high of a yield of hydrogen or as high of a gaseous flow rate. The process of supercritical water gasification of carbonyl groups seemingly follows the same reactivity trend as that of general nucleophilic attack of carbonyls:

푎푙푑푒ℎ푦푑푒푠 > 푐푎푟푏표푥푦푙푖푐 푎푐푖푑푠 > 푎푚푖푑푒푠

This conclusion leads one to believe that the supercritical water gasification process itself, at least when carbonyl groups are present, occurs via the nucleophilic attack of water towards these carbonyl groups.

Acetic acid gasification was broken up into two groups: the first two gasification reactions that had a high yield and high effluent flow rate and the last three gasification reactions that had a low yield and low effluent flow rate. The last three experimental runs were verified by previous studies.25,33 It was postulated that one of three methods was responsible for the relatively high equimolar amounts of CO2 and CH4 as well as the low hydrogen yield: the Sabatier reaction alone, the decarboxylation of acetic acid, or by a series of reactions that included conversion of acetic acid into acetone followed by decomposition into ethylene and methane. The Sabatier reaction is generally catalyzed by

58 nickel catalysts, which would explain a catalytic effect by the high nickel alloys that compose the reactor. A shift in the water-gas shift reaction would have to account for the carbon monoxide. The second mechanism is the decarboxylation of acetic acid, which does not account for the carbon monoxide that is present. Other side reactions are needed as well. It is likely that acetic acid gasification occurs via a series of reactions including the formation of acetone from acetic acid (Reaction 8), the decomposition of acetone into ethylene (Reaction 9), the cracking of ethylene into carbon and hydrogen that form methane (Reaction 10), and the subsequent shift in the water gas-shift and Sabatier reaction equilibria. This pathway stoichiometrically accounts for the relative amounts of gases present in the effluent stream as well as the production of coke that was identified in the downstream filters after experimentation was completed (Figure C10).

Acetaldehyde gasification occurred much more readily and produced a much more hydrogen rich product stream with higher effluent flow rates and is verified by previous work.27 It is likely that acetaldehyde gasification proceeds via the breakdown of acetaldehyde into methane and carbon monoxide with other side reactions producing hydrogen and carbon dioxide and shifting the water gas shift reaction or through the reaction of acetaldehyde with itself to form acetone, hydrogen gas, and carbon monoxide.

This formation, along the breakdown of acetone (Reactions 9 and 10), account for the higher amount of hydrogen than predicted solely from the breakdown of acetaldehyde.

Acetamide, a largely unstudied hydrocarbon in terms of supercritical water chemistry, produces a similar hydrogen yield and effluent flow rate as that of acetic acid gasification, but with significantly less amounts of carbon dioxide present in the gas

59 stream. This is likely due the acetamide hydrolyzing into acetic acid and ammonia and gasifying in a similar manner to that of acetic acid. However, the ammonia makes the resulting water, once cooled and depressurized, basic, which allows for more CO2 to dissolve into the water and thus removes it from the gaseous effluent and accounts for the lower mole fraction of carbon dioxide than that of acetic acid gasification. Liquid analysis would be needed to verify this claim.

Going forward, suggested continued research to extend on the impact and validity of this work include:

 Testing the water effluent throughout the gasification process to determine

intermediates formed especially in acetamide gasification to verify the presence of

dissolved CO2 in the liquid.

 Performing further gasification experiments on acetamide to verify the

reproducibility of these experiments and on other low chain amides to get a better

understanding of the gasification of amides in general.

 Performing further experiments at differing temperatures and residence times to

develop reaction mechanisms and kinetic models that more fully explain the

gasification process.

 Determining the catalytic efficacy of both Haynes 282 and Inconel 625 (Grade II)

on the reactions that occur in the supercritical water gasification process

especially in regards to the catalytic efficacy of Haynes 282 towards acetic acid

gasification.

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APPENDIX A: DATA ANALYSIS INFORMATION

A1: Density and Molecular Weight Data

Table A1. Density and molar mass of gases that constitute syngas Density (~23 C) Molar Mass Gas (g/mL) (g/mol)

H2 8.38E-05 2.0159 CO 1.65E-03 58.9332

CO2 1.84E-03 44.0095

CH4 6.68E-04 16.0425

C2H6 1.26E-03 30.069

C2H4 1.26E-03 28.0532

Table A2. Density and molar mass of chemical feedstocks utilized at 25 °C Density Molar Mass Feed Stock (g/mL) (g/mol) Acetaldehyde 0.788 44.05 Acetic Acid 1.05 60.05 Acetamide 1.16 59.07

A2: List of Symbols

Latin Letters 푚퐿 푣̇ = 푣표푙푢푚푒 푓푙표푤푟푎푡푒 ( ) 푚푖푛

푚표푙 푛̇ = 푚표푙푎푟 푓푙표푤푟푎푡푒 ( ) 푚푖푛

푔 푚̇ = 푚푎푠푠 푓푙표푤푟푎푡푒 ( ) 푚푖푛

푚퐿 푤̇ = 푤푎푡푒푟 푣표푙푢푚푒 푓푙표푤푟푎푡푒 ( ) 푚푖푛

푔 퐶 = 푓푒푒푑 푐표푛푐푒푛푡푟푎푡푖표푛 ( ) 푚퐿

푥 = 푚표푙푒 푓푟푎푐푡푖표푛

푔 푀푀 = 푚표푙푎푟 푚푎푠푠 ( ) 푚표푙

푇 = 푡푒푚푝푒푟푎푡푢푟푒 (298 퐾)

퐿 푎푡푚 푅 = 푔푎푠 푐표푛푠푡푎푛푡 (0.08206 ) 푚표푙 퐾

푃 = 푝푟푒푠푠푢푟푒 (1 푎푡푚)

퐺퐸 = 푔푎푠푖푓푖푐푎푡푖표푛 푒푓푓푖푐푖푒푛푐푦 (%)

퐶퐸 = 푐푎푟푏표푛 푒푓푓푖푐푖푒푛푐푦 (%)

푔 푅푎푡푒 = 푔푎푠푖푓푖푐푎푡푖표푛 푟푎푡푒 ( ) 푚퐿 푠

푌 = ℎ푦푑푟표푔푒푛 푦푖푒푙푑 (%)

푛 = 푛푢푚푏푒푟 표푓 푖푛푗푒푐푡푖표푛푠 푓표푟 퐺퐶 푐푎푙푖푏푟푎푡푖표푛 푐푢푟푣푒푠

훼 푡 ,푛−2 = 푐푟푖푡푖푐푎푙 푣푎푙푢푒 푓표푟 푡ℎ푒 푡 푑푖푠푡푟푖푏푢푡푖표푛 2 푎 = 푎푟푒푎 표푓 퐺퐶 푝푒푎푘

푦 = 푣표푙푢푚푒 표푓 푔푎푠 푟푒푙푎푡푒푑 푡표 퐺퐶 푝푒푎푘

Greek Letters

푔 휌 = 푑푒푛푠푖푡푦 ( ) 푚퐿

휏 = 푟푒푠푖푑푒푛푐푒 푡푖푚푒 (푠푒푐표푛푑푠)

훿 = 푒푟푟표푟

Subscripts 푓 = 푔푒푛푒푟푎푙 푓푢푒푙 푓푒푒푑 퐴푐푎 = 퐴푐푒푡푖푐 푎푐푖푑 퐴푐푚 = 퐴푐푒푡푎푚푖푑푒

퐴푐ℎ = 퐴푐푒푡푎푙푑푒ℎ푦푑푒 푠표푙 = 퐴푐푒푡푎푚푖푑푒⁄푤푎푡푒푟 푠표푙푢푡푖표푛 푒 = 퐺푎푠 푒푓푓푙푢푒푛푡 (푠푦푛푔푎푠) 퐻2 = 퐻푦푑푟표푔푒푛 퐶푂 = 퐶푎푟푏표푛 푚표푛표푥푖푑푒 퐶푂2 = 퐶푎푟푏표푛 푑푖표푥푖푑푒 퐶퐻4 = 푀푒푡ℎ푎푛푒 퐶2퐻6 = 퐸푡ℎ푎푛푒 퐶2퐻4 = 퐸푡ℎ푦푙푒푛푒 푖, 푗 = 푎푛 푖푛푑푖푣푖푑푢푎푙 푡푒푟푚

Superscripts

∗ = 푝표푖푛푡 푖푛 푟푒푔푟푒푠푠푖표푛

− = 푎푣푒푟푎푔푒

A3: Acetamide Flowrate Calculation

To prepare the acetamide for feeding into the reactor, an aqueous solution needed to be prepared as the melting point of acetamide would be too high for practical use in the pump. To do this, a factor relating the solution flowrate to the pure water flowrate (F) as well as the concentration of the acetamide solution need to be calculated. Below are those calculations. As a starting point, a 750 gram solution to 1 liter of water was selected.

1 푚퐿 1 퐿 750 푔 퐴푐푒푡푎푚푖푑푒 ∗ ( ) ∗ ( ) = 0.648 퐿 퐴푐푒푡푎푚푖푑푒 1.154 푔 1000 푚퐿

0.648 퐿 퐴푐푒푡푎푚푖푑푒 1 퐿 퐻 푂 0.393 퐿 퐴푐푒푡푎푚푖푑푒 ( ) ∗ ( 2 ) = 1 퐿 퐻2푂 1.648 퐿 푠표푙푢푡푖표푛 1 퐿 푠표푙푢푡푖표푛

Assuming a flowrate of the solution of 1 mL/min,

0.393 푚퐿 퐴푐푒푡푎푚푖푑푒

0.607 푚퐿 퐻2푂

To solve for F,

0.393 1 = 0.607 + 퐹 10

3.93 = .607 + 퐹

퐹 = 3.323

Solving via ASPEN Plus with the Peng-Robinson equation of state with Wong-Sandler mixing rules, the flowrates needed to have a factor of 3.323 were:

푚퐿 퐴푐푒푡푎푚푖푑푒 푠표푙푢푡푖표푛 푓푙표푤푟푎푡푒 = 4.32 푚푖푛 푚퐿 푊푎푡푒푟 푓푙표푤푟푎푡푒 = 14.36 푚푖푛

As a check,

4.32 푚퐿 푠표푙푢푡푖표푛 0.393 푚퐿 퐴푐푒푡푎푚푖푑푒 푚퐿 ( ) ∗ ( ) = 1.7 퐴푐푒푡푎푚푖푑푒 1 푚푖푛 1 푚퐿 푠표푙푢푡푖표푛 푚푖푛

4.32 푚퐿 푠표푙푢푡푖표푛 푚퐿 푚퐿 ( ) ∗ (1 − .393) + 14.36 = 17 푊푎푡푒푟 1 푚푖푛 푚푖푛 푚푖푛

A4: Acetaldehyde Calculations

푚̇ 퐴푐ℎ = 푣̇퐴푐ℎ ∗ 휌퐴푐ℎ

푚̇ 퐴푐ℎ 푛̇퐴푐ℎ = 푀푀퐴푐ℎ

푚̇ 퐶 = 퐴푐ℎ 퐴푐ℎ 푤̇

푃 휌 = ( ) 푒 1000 ∗ 푇 ∗ 푅 ∗ (푥퐻2 ∗ 푀푀퐻2 + 푥퐶푂 ∗ 푀푀퐶푂 + 푥퐶푂2 ∗ 푀푀퐶푂2 + 푥퐶퐻4 ∗ 푀푀퐶퐻4 + 푥퐶2퐻6 ∗ 푀푀퐶2퐻6 + 푥퐶2퐻4 ∗ 푀푀퐶2퐻4)

푀푀푒 = 푥퐻2 ∗ 푀푀퐻2 + 푥퐶푂 ∗ 푀푀퐶푂 + 푥퐶푂2 ∗ 푀푀퐶푂2 + 푥퐶퐻4 ∗ 푀푀퐶퐻4 + 푥퐶2퐻6 ∗ 푀푀퐶2퐻6 + 푥퐶2퐻4 ∗ 푀푀퐶2퐻4

푚̇ 푒 = 푣푒̇ ∗ 휌푒

푚̇ 푒 푛̇ 푒 = 푀푀푒

푚̇ 푒 퐺퐸퐴푐ℎ = ∗ 100 푚̇ 퐴푐ℎ

푛̇ 푒 퐶퐸퐴푐ℎ = ( ) ∗ (푥퐶푂 + 푥퐶푂2 + 푥퐶퐻4 + 2 ∗ 푥퐶2퐻6 + 2 ∗ 푥퐶2퐻4) ∗ 100 2 ∗ 푛̇퐴푐ℎ

퐶 ∗ 퐺퐸 푅푎푡푒 = 퐴푐ℎ 퐴푐ℎ 퐴푐ℎ 휏

푛̇ 푒 ∗ 푥퐻2 푌퐴푐ℎ = 푛̇퐴푐ℎ

A5: Acetic Acid Calculations

푚̇ 퐴푐푎 = 푣̇퐴푐푎 ∗ 휌퐴푐푎

푚̇ 퐴푐푎 푛̇퐴푐푎 = 푀푀퐴푐푎

푚̇ 퐶 = 퐴푐푎 퐴푐푎 푤̇

푀푀푒 = 푥퐻2 ∗ 푀푀퐻2 + 푥퐶푂 ∗ 푀푀퐶푂 + 푥퐶푂2 ∗ 푀푀퐶푂2 + 푥퐶퐻4 ∗ 푀푀퐶퐻4 + 푥퐶2퐻6 ∗ 푀푀퐶2퐻6 + 푥퐶2퐻4 ∗ 푀푀퐶2퐻4

푚̇ 푒 = 푣푒̇ ∗ 휌푒

푚̇ 푒 푛̇ 푒 = 푀푀푒

푚̇ 푒 퐺퐸퐴푐푎 = ∗ 100 푚̇ 퐴푐푎

푛̇ 푒 퐶퐸퐴푐푎 = ( ) ∗ (푥퐶푂 + 푥퐶푂2 + 푥퐶퐻4 + 2 ∗ 푥퐶2퐻6 + 2 ∗ 푥퐶2퐻4) ∗ 100 2 ∗ 푛̇퐴푐푎

퐶 ∗ 퐺퐸 푅푎푡푒 = 퐴푐푎 퐴푐푎 퐴푐푎 휏

푛̇ 푒 ∗ 푥퐻2 푌퐴푐푎 = 푛̇퐴푐푎

A6: Acetamide Calculations

0.393 푚퐿 푎푐푒푡푎푚푖푑푒 푣̇ = 푣̇ ∗ 퐴푐푚 푠표푙 1 푚퐿 푠표푙푢푡푖표푛

푚̇ 퐴푐푚 = 푣퐴푐̇ ∗ 휌퐴푐푚

푚̇ 퐴푐푚 푛̇퐴푐푚 = 푀푀퐴푐푚

푚̇ 퐴푐푚 퐶퐴푐푚 = 푤̇ + 푣̇푠표푙 − 푣̇퐴푐푚

푀푀푒 = 푥퐻2 ∗ 푀푀퐻2 + 푥퐶푂 ∗ 푀푀퐶푂 + 푥퐶푂2 ∗ 푀푀퐶푂2 + 푥퐶퐻4 ∗ 푀푀퐶퐻4 + 푥퐶2퐻6 ∗ 푀푀퐶2퐻6 + 푥퐶2퐻4 ∗ 푀푀퐶2퐻4

푚̇ 푒 = 푣푒̇ ∗ 휌푒

푚̇ 푒 푛̇ 푒 = 푀푀푒

푚̇ 푒 퐺퐸퐴푐푚 = ∗ 100 푚̇ 퐴푐푚

푛̇ 푒 퐶퐸퐴푐푚 = ( ) ∗ (푥퐶푂 + 푥퐶푂2 + 푥퐶퐻4 + 2 ∗ 푥퐶2퐻6 + 2 ∗ 푥퐶2퐻4) ∗ 100 2 ∗ 푛̇퐴푐푚

퐶 ∗ 퐺퐸 푅푎푡푒 = 퐴푐푚 퐴푐푚 퐴푐푚 휏

푛̇ 푒 ∗ 푥퐻2 푌퐴푐푚 = 푛̇퐴푐푚

A7: Error Calculations/Propagation

Throughout calculations made, error needed to be propagated. This section shows how error was propagated from known values of the water and fuel feed flow rates as well as the effluent flow rate along with error values obtained from the regression into the calculated results of mole fractions, yield, gasification efficiency, carbon efficiency, and gasification rate.

The error on the slopes (m) and intercepts (b) for each calibration curve is calculated using Excel’s regression tool and can be seen in Table A3.

Table A3. Slopes, intercepts, and their errors for the GC calibration curves Gas M ± B ±

H2 0.0006 0.00002 0.0119 0.0151 CO 0.0058 0.0005 0.0713 0.0233

CO2 0.0060 0.00005 -0.0134 0.0038

CH4 0.0019 0.00002 -0.0007 0.0026

C2H6 0.0017 0.00001 -0.0018 0.0022

C2H4 0.0018 0.0001 0.0060 0.0053

Calculating the error using for an unknown data point, in this case the volume

(y*) of an injection from a given area (a*) is done in the following manner.

∑(푦 − 푚푎 − 푏)2 푆 = √ 푖 푖 푛 − 2

1 푛 ∗ (푎∗ − 푎̅)2 ∗ 훼 훿푦 = 푡 ,푛−2 ∗ 푆 ∗ √ + 2 2 2 푛 푛∑푎푖 − (∑푎푖)

For calculations, 95% confidence intervals were used so α was equal to 0.05 and the critical t was calculated via Excel’s t.inv command. For propagating error through calculations that involved addition or subtraction, the following equation was used:

2 훿푗 = √∑(훿푖)

To propagate error through calculations involving multiplication and division, the following formula was used:

2 훿푗 훿 = √∑ ( 푖) 푗 푖

Shown next are sample error propagations for mole fraction, yield, gasification efficiency, carbon efficiency, and gasification rate.

Mole Fraction for a single injection

2 2 훿 ∗ ∑훿 ∗ √ 푦 푦푖 훿푥 = 푥 ∗ ( ∗ ) + ( ∗ ) 푦 ∑푦푖

Hydrogen Yield

훿푣̇ 푓 훿푛̇ 푓 = 푛̇푓 ∗ 푣푓̇

where 훿푣̇ 푓 is equal to 0.0005 ml/min (from the fuel feed pump).

훿 2 훿 2 √ 푀푀푒 푚̇ 푒 훿푛̇ 푒 = 푛̇ 푒 ∗ ( ) + ( ) 푀푀푒 푚̇ 푒

2 훿푀푀푒 = √∑(훿푥푖)

훿 2 훿 2 √ 푣̇푒 휌푒 훿푚̇ 푒 = 푚̇ 푒 ∗ ( ) + ( ) 푣푒̇ 휌푒

where 훿푣̇푒is equal to 5 ml/min (from the LabVIEW control system).

2 훿휌푒 = √∑(훿푥푖)

훿 2 2 훿 2 푛̇ 푓 훿푛̇ 푒 푥퐻2 훿푌 = 푌 ∗ √( ) + ( ) + ( ) 푛̇푓 푛̇ 푒 푥퐻2

Gasification Efficiency

훿푣̇ 푓 훿푚̇ 푓 = 푚̇ 푓 ∗ 푣푓̇

훿 2 2 푚̇ 푓 훿푚̇ 푒 훿퐺퐸 = 퐺퐸 ∗ √( ) + ( ) 푚̇ 푓 푚̇ 푒

Carbon Efficiency

2 2 2 2 2 2 훿푥퐶푂 훿푥퐶푂2 훿푥퐶퐻4 훿푥퐶2퐻6 훿푥퐶2퐻4 훿푛̇ 푒 훿퐶퐸 = 퐶퐸 ∗ √( ) + ( ) + ( ) + ( ) + ( ) + ( ) 푥퐶푂 푥퐶푂2 푥퐶퐻4 푥퐶2퐻6 푥퐶2퐻4 푛̇ 푒

Gasification Rate

훿 2 2 2 푛̇ 푓 훿푛̇ 푒 훿푥퐻2 훿푅푎푡푒 = 푅푎푡푒 ∗ √( ) + ( ) + ( ) 푛̇푓 푛̇ 푒 푥퐻2

APPENDIX B: GAS CHROMATOGRAPHY INFORMATION

B1: Gas Chromatography Instrument Method

Carrier/Reference Gas: Argon

Flow Mode: Pressure controlled

Inlet Temperature: 100 °C

Temperature: 40 °C for 9.25 minutes then ramp to 200 °C at 40 °C/minute and stay at

200 °C till the end (20 minutes total time)

Pressure: 1.93 bar

Detector Polarity: Negative

Data Collection Rate – 120 Hz

TCD Signal Source: DetA

Detector Temperature – 190 °C

Base Temperature – 200 °C

Filament Voltage – 10 V

Makeup Flow: 5.0 ml/min

Reference Flow: 40.0 ml/min

B2: Calibration Curves

0.8

0.7

0.6

0.5 y = 0.0006x + 0.0119 0.4 R² = 0.996

Volume(mL) 0.3

0.2

0.1

0 0 200 400 600 800 1000 1200 1400 Area (mV*min)

Figure B1. Hydrogen calibration curve

0.6

0.5

0.4 y = 0.0058x + 0.0713 R² = 0.931

0.3 Volume(mL) 0.2

0.1

0 0 10 20 30 40 50 60 70 80 90 Area (mV*min)

Figure B2. Carbon monoxide calibration curve

0.9

0.8

0.7

0.6 y = 0.0060x - 0.0134 0.5 R² = 0.9994

0.4 Volume(mL)

0.3

0.2

0.1

0 0 20 40 60 80 100 120 140 160 180 Area (mV*min)

Figure B3. Carbon dioxide calibration curve

0.45 0.4 0.35 0.3 0.25 y = 0.0019x - 0.0007 0.2 R² = 0.9994

Volume(mL) 0.15 0.1 0.05 0 0 50 100 150 200 250 Area (mV*min)

Figure B4. Methane calibration curve

0.6

0.5

0.4 y = 0.0017x - 0.0018 R² = 0.9999

0.3 Volume(mL) 0.2

0.1

0 0 50 100 150 200 250 300 350 Area (mV*min)

Figure B5. Ethane calibration curve

0.25

0.2

0.15

y = 0.0018x + 0.0060 R² = 1.0000

Volume(mL) 0.1

0.05

0 0 20 40 60 80 100 120 Area (mV*min)

Figure B6. Ethylene calibration curve

B3: Calibration Injections

To calibrate the GC, the following standard gases, purchased from Praxair, were injected at a volume of 1 mL with a pressure-lock gas syringe.

Table B1. Standard gases used for calibration (Note: Gas 7 also had 15.1% butylene and 15.0% propylene and was only used to calibrate ethylene) Composition Percentage Gas H2 CO CO2 CH4 C2H6 C2H4 Number 1 0.0% 50.1% 0.0% 0.0% 49.9% 0.0% 2 38.0% 40.2% 1.0% 1.0% 19.8% 0.0% 3 0% 0% 100% 0% 0% 0% 4 5.14% 5.00% 39.30% 40.50% 5.02% 5.00% 5 60.21% 0.00% 9.89% 10.10% 0.00% 19.80% 6 69.97% 14.70% 10.20% 5.13% 0.00% 0.00% 7 10.20% 9.86% 9.96% 19.88% 0.00% 20.00%

The following figures are the GC plots of the calibration standard injections used for the calibration curves with the peak information below the plots. Each gas was injected three times and the average areas were plotted and used for the calibration curves. As a note, the peaks for the GC injections for both calibration injections and actual experimental injections have a tailing effect. This is likely due to an issue with the

GC injector and results in having a higher uncertainty for the areas and subsequent associated volumes.

Figure B7. Calibration Gas Number 1 injection number 1 79

Figure B8. Calibration Gas Number 1 injection number 2 80

Figure B9. Calibration Gas Number 1 injection number 3 81

Figure B10. Calibration Gas Number 2 injection number 1 82

Figure B11. Calibration Gas Number 2 injection number 2 83

Figure B12. Calibration Gas Number 2 injection number 3 84

Figure B13. Calibration Gas Number 3 injection number 1 85

Figure B14. Calibration Gas Number 3 injection number 2 86

Figure B15. Calibration Gas Number 3 injection number 3 87

Figure B16. Calibration Gas Number 4 injection number 1 88

Figure B17. Calibration Gas Number 4 injection number 2 89

Figure B18. Calibration Gas Number 4 injection number 3 90

Figure B19. Calibration Gas Number 5 injection number 1 91

Figure B20. Calibration Gas Number 5 injection number 2 92

Figure B21. Calibration Gas Number 5 injection number 3 93

Figure B22. Calibration Gas Number 6 injection number 1 94

Figure B23. Calibration Gas Number 6 injection number 2 95

Figure B24. Calibration Gas Number 6 injection number 3 96

Figure B25. Calibration Gas Number 7 injection number 1 97

Figure B26. Calibration Gas Number 7 injection number 2 98

Figure B27. Calibration Gas Number 7 injection number

100

APPENDIX C: PHOTOS AND DIAGRAMS

The photos seen here are supplementary to the understanding of the thesis as a whole. Included in this appendix are pictures of the reactor unit used and a screenshot of the LabVIEW control system interface.

Pneumatic Control Valve

Liquid Reactor Vapor Separation Bomb Integrated Heat Exchanger Preheater

101 Figure C1. Custom built reactor unit (gray box on the right is the reactor and white cylinder on the left is the water preheater)

Figure C2. Angled view of the reactor 102

Figure C3. Front view of reactor unit including gas sampling port (top left), liquid product drain (bottom right), and valves 103 for feeding and emptying reactor

104

Figure C4. Close-up view of gas sampling portion of the reactor with a gas sampling port (red arrow) and thermocouple

Figure C5. Close-up view of valve system 105

Figure C6. LabVIEW control system interface

106

107

Figure C7. Temperature and pressure control portion of LabVIEW interface

Figure C8. Temperature and pressure monitoring portion of the LabVIEW interface

108

109

Figure C9. Gas monitoring section and integrated PFD of the LabVIEW interface

110

Figure C10. Solid gathered from filters

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