MORRILL-DISSERTATION-2013

122 Pages·2014·6.63 MB·English

by  Michael Morrill

HIGHER ALCOHOL SYNTHESIS ON MAGNESIUM/ALUMINUM
MIXED OXIDE SUPPORTED POTASSIUM CARBONATE
PROMOTED MOLYBDENUM SULFIDE

A Dissertation
Presented to
The Academic Faculty

by

Michael Robert Morrill

In Partial Fulfillment
of the Requirements for the Degree
Doctor of Philosophy in the
School of Chemical & Biomolecular Engineering

Georgia Institute of Technology
August 2013

COPYRIGHT ® 2013 BY MICHAEL R. MORRILL
i
HIGHER ALCOHOL SYNTHESIS ON MAGNESIUM/ALUMINUM
MIXED OXIDE SUPPORTED POTASSIUM CARBONATE
PROMOTED MOLYBDENUM SULFIDE

Approved by:

Dr. Christopher W. Jones, Co-Advisor Dr. Pradeep K. Agrawal, Co-Advisor
School of Chemical & Biomolecular School of Chemical & Biomolecular
Engineering Engineering
Georgia Institute of Technology Georgia Institute of Technology

Dr. David S. Sholl Dr. Dennis W. Hess
School of Chemical & Biomolecular School of Chemical & Biomolecular
Engineering Engineering
Georgia Institute of Technology Georgia Institute of Technology

Dr. Faisal Alamgir Dr. Jake D. Soper
School of Materials Science and School of Chemistry and Biochemistry
Engineering Georgia Institute of Technology
Georgia Institute of Technology

Date Approved: July, 1st, 2013
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ACKNOWLEDGMENTS

I wish to thank my thesis advisors, Dr. Christopher Jones and Dr. Pradeep
Agrawal for their constant support, patience, and technical guidance. I also express
gratitude to The Dow Chemical Company for their financial support and Dr. Daniela
Ferrari and Dr. David Barton for their input and feedback on behalf of the company. Dr.
Robert Davis and Heng Shou at the University of Virginia provided tremendous support
and instruction in helping me learn about X-ray absorption. I owe a great deal of my
education to their efforts.
I express appreciation to my thesis committee members – Dr. Dennis W. Hess,
Dr. David S. Sholl, Dr. Faisal Alamgir, and Dr. Jake D. Soper for their input and
criticism during my PhD proposal. Dr. Megan Lydon, Dr. Heng Shou, and the Jones
research group at Georgia Tech provided me with friendship and assistance that made
graduate school enjoyable. Finally, I wish to thank Dr. Kinga Unicioc from Oak Ridge
National Lab and Dr. Bruce Ravel at Brookhaven National Lab for their assistance and
invaluable pedagogy.

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TABLE OF CONTENTS
Page
ACKNOWLEDGMENTS III

LIST OF TABLES VII

LIST OF FIGURES VIII

LIST OF SYMBOLS AND ABBREVIATIONS XII

SUMMARY XIV

CHAPTER 1: INTRODUCTION 1

1-1 Syngas 1

1-2 MoS /K as selective catalyst for higher alcohols from syngas 1

2
1-3 Supports for MoS /K 2

2
1-4 Importance of Mo-K interactions 4

1-5 Reaction pathways and Mo structural significance 4

1-6 Significance of Mo loading 6

1-7 Alcohol coupling 7

1-8 Topics of this dissertation 8

CHAPTER 2: INVESTIGATION OF BASIC SUPPORTS 9

2-1 Experimental details 9

2-2 XRD measurements 15

2-3 Raman Spectroscopy 16

2-4 Nitrogen Physisorption 17

2-5 Reactivity Results 18

2-6 Summary 23

iv
CHAPTER 3: ROLE OF MMO IN ALCOHOL FORMING REACTIONS 24

3-1 Experimental details 25

3-2 XRD 28

3-3 N Physisorption 29

2
3-4 Raman spectroscopy 30

3-5 UV-vis DRS 32

3-6 STEM 33

3-7 XAS 35

3-8 Reaction Results and Discussion 41

3-9 Summary 59

CHAPTER 4: ALCOHOL CO-FEEDS AND COUPLING 60

4-1 Experimental setup 60

4-2 Results and Discussion 62

4-3 Conclusions 75

CHAPTER 5: CONCLUSIONS AND OUTLOOK 77

APPENDIX A: MMO IMPREGNATION 81

APPENDIX B: CONTROLLING SYNGAS COMPOSITION 85

APPENDIX C: SYSTEM CONTROL AND DESIGN CONSIDERATIONS 88

APPENDIX D: ESTIMATING TRANSPORT PARAMETERS 91

D-1 Internal Mass Transport Effects (Weisz-Prater Criterion) 91

D-2 External Heat Transfer (“Hotspots”) 93

APPENDIX E: ADDITIONAL CONTROL EXPERIMENTS 94

E-1 Reaction 94

E-2 Using XANES to Monitor Mo Oxidation 97

v
REFERENCES 100

VITA 106

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LIST OF TABLES

Page
Table 2.1. Summary of reaction parameters 13

Table 2.2. Pre-reaction/sulfidation catalyst and sulfided, reaction aged catalyst
compositions and surface areas measured via ICP and nitrogen
physisorption respectively. 18

Table 2.3. Reaction results of supported and unsupported MoS Catalysts. 19

2
Table 2.4. NH and CO TPD results for supports used in this study. 20

3 2
Table 3.1. BET surface area derived from nitrogen physisorption data for the
materials used in this study. 30

Table 3.2. Results from the Analysis of Mo K edge EXAFS 39

Table 3.3. Reactivity results for samples used in study. 46

Table 3.4.BET surface area and elemental analysis results for samples used in
study. 52

Table 4.1. Carbon balances for methanol and ethanol co-feed experiments 66

Table E.1 Reactivity data for various catalysts used in control experiments 97

vi i
LIST OF FIGURES

Page
Figure 2.1. GC sample loop, column schematics, and plumbing diagram of the
instrument used in study. 15

Figure 2.2. XRD of supported and unsupported K CO promoted MoS .
2 3 2
Supported samples were sulfided in-situ and reacted with syngas for
2-4 days. 16

Figure 2.3. Raman spectroscopy of the reaction-aged, sulfided catalysts using a
1800 grating, 514 nm, 0.5 mW laser 17

Figure 2.4. The ASF distribution of alcohols (a) and hydrocarbons (b) on various
supported and unsupported potassium promoted MoS catalysts. The
2
α values (chain growth parameters) were computed for C – C linear
2 4
alcohols and for C – C linear hydrocarbons. 22

1 4
Figure 3.1. XRD data of supported and unsupported K CO promoted MoS .
2 3 2
Supported samples were sulfided in-situ and reacted with syngas for
2-4 days. 29

Figure 3.2. Raman spectra of the MMO supported Mo/K materials precatalysts
pretreated in nitrogen (a) and air (b) both analyzed with a 1.5 mW 514
nm laser. The sulfided, reacted catalyst (c) was analyzed with a 0.5
mW 514 nm laser. 31

Figure 3.3. UV-vis DRS spectra for bulk MoO (from decomposed AMT),
3
Mo/MMO-15, and Mo/MMO-5. Samples in (a) were pretreated at 450
°C in nitrogen while samples in (b) were pretreated in air at the same
temperature. 33

Figure 3.4. STEM images of Mo/K/MMO-5,3 (a) and (b) and Mo/K/MMO-15,9
(c) and (d) after sulfidation and reaction with syngas. Unreacted bulk
MoS is shown in (e) and (f) for reference. 34

2
Figure 3.5. XANES Mo K-edge spectra of the 5 % and 15 % Mo supported MMO
samples after combination with K CO , presulfidation, and reaction
2 3
with CO. 36

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Figure 3.6. Fourier transform (not corrected for phase shifts) of k3-weighted Mo K
edge EXAFS of: (a) Mo/K/MMO-5,3, sulfided and reacted; (b)
Mo/K/MMO-15,9, sulfided and reacted; (c) bulk MoS standard.
2
Spectra are offset for clarity. (Figure created by University of Virginia
collaborator Dr. Heng Shou.) 38

Figure 3.7. Comparison of the curve fit to experimental Mo K edge EXAFS of
Mo/K/MMO-15,9 (sulfided and reacted): (a) k3-Weighted Mo K edge
EXAFS (solid line) and the result from curve fit (circles); (b)
magnitude (solid line) and the imaginary part (dashed line) of the
Fourier transform of EXAFS compared with the result from the curve
fit (circles). (Figure created by University of Virginia collaborator Dr.
Heng Shou.) 40

Figure 3.8. Alcohol and hydrocarbon selectivity (CO -free) vs. CO conversion for
2
C to C alcohols over MMO supported catalysts, Mo/K/MMO-5,3,
1 4
Mo/K/MMO-15,9, and Mo/K/MMO-5,9. 45

Figure 3.9. Average alcohol and hydrocarbon selectivity (CO -free) vs. CO
2
conversion over three replicate batches for methane and ethane over
the two MMO supported catalysts, Mo/K/MMO-5,3 and
Mo/K/MMO-15,9 with error bars representing 1 standard deviation. 47

Figure 3.10. Catalyst bed schematics showing the various combinations of Mo, K,
and MMO used in reaction. Cases a. and b. represent the base cases
for the study. Case c. (not shown) represents the same catalyst as case
a. but with a higher K content. Case d. is the combination of catalyst
b. and bare MMO in series such that the final overall bed composition
is the same as case a. Case e. represents the same materials as case d.
but ground into a homogeneous phase. Case f. was prepared similarly
to e. but bulk MoS was used as the Mo source instead of
2
Mo/K/MMO-15,9. Cases a., d., e., and f. represent catalyst beds with
the same total amounts of MoS , K CO , and MMO in the bed. 50

2 2 3
Figure 3.11. XRD patterns of Mo/K/MMO catalysts and precatalyst along with
bulk MoS references. Mo/K/MMO-15,9-MMOg-O has similar oxide
2
domains to Mo/K/MMO-15,9-O while Mo/K/MMO-15,9-MMOg-SR
has similar sulfide domains to Mo/K/MMO-5,3-SR. The notation “-
SR” denotes a catalyst that has been sulfided and used in reaction.
The notation “-O” denotes a catalyst that in its oxide precatalyst form. 51

Figure 3.12. Alcohol and hydrocarbon selectivity (CO -free) vs. CO conversion
2
for C to C alcohols over MMO supported catalysts, Mo/K/MMO-
1 4
5,3, Mo/K/MMO-15,9, Mo/K/MMO-15,9-MMOs, Mo/K/MMO-15,9-
MMOg, and Mo/K-bulk-MMOg. 55

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Figure 3.13. Catalyst bed schematics for reactions with added MMO/K showing
MMO/K combined with Mo/K/MMO-15,9 in series – Mo/K/MMO-
15,9-MMO/Ks (f), or mixed as particles – Mo/K/MMO-15,9-
MMO/Km (g). 57

Figure 3.14. Alcohol and hydrocarbon selectivity (CO -free) vs. CO conversion
2
for C to C alcohols over MMO supported catalysts combined with
1 4
MMO/K – Mo/K/MMO-15,9-MMO/Ks and Mo/K/MMO-15,9-
MMO/Ks. Mo/K/MMO-5,3, Mo/K/MMO-5,9, Mo/K/MMO-15,9, and
Mo/K/MMO-15,9-MMOs shown for reference. 58

Figure 4.1. Simplified schematic of reactor retrofitted with an Isco syringe pump.
The back pressure regulator between the GC and the reactor was
removed from the schematic for simplicity. 61

Figure 4.2. Carbon balance and lumped product distributions for methanol feed
experiments over Mo/K/MMO-5,3 (a) and Mo/K-bulk (b). 64

Figure 4.3. Carbon balance and lumped product distributions for ethanol feed
experiments over Mo/K/MMO-5,3 (a) and Mo/K-bulk (b). 65

Figure 4.4. Major product distributions of the methanol feed over Mo/K/MMO-
5,3 (a) and Mo/K-bulk (b). 68

Figure 4.5. Minor product distributions of oxygenates other than linear alcohols
for the methanol feed over Mo/K/MMO-5,3 (a) and Mo/K-bulk (b). 70

Figure 4.6. Carbon balance (a) and major product distributions (b) for syngas and
methanol fed over MMO/K-3. 71

Figure 4.7. Reactivity results for major products of the ethanol feed over
Mo/K/MMO-5,3 (a) and Mo/K-bulk (b). 73

Figure 4.8. Product distributions of oxygenates other than linear alcohols for the
ethanol feed over Mo/K/MMO-5,3 and Mo/K-bulk 75

Figure A.1 XRD patterns of MMO impregnated with aqueous solutions of AMT
and K CO 82

2 3.
Figure A.2 XRD patterns of MMO impregnated with DMSO solution of AMT
and ground with dry K CO . 84

2 3
Figure B.1 A simplified plumbing and instrumentation diagram (P&ID) of the
packed bed reactor system. 86

Figure C.1. The LabView® subVI that writes pressure, temperature, and flow
meta data to an array of 43,200 points and overwrites the oldest points
once the array has been filled. 89

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