The Reactivity of Multifunctional Alcohols on Palladium Surfaces and Supported Catalysts

142 Pages·2017·3.55 MB·English

University of Colorado, Boulder
CU Scholar
Chemical & Biological Engineering Graduate
Chemical & Biological Engineering
Theses & Dissertations
Spring 1-1-2013
The Reactivity of Multifunctional Alcohols on
Palladium Surfaces and Supported Catalysts
Michael Brandon Griffin
University of Colorado at Boulder, [email protected]
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Recommended Citation
Griffin, Michael Brandon, "The Reactivity of Multifunctional Alcohols on Palladium Surfaces and Supported Catalysts" (2013).
Chemical & Biological Engineering Graduate Theses & Dissertations. 37.
https://scholar.colorado.edu/chbe_gradetds/37
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The Reactivity of Multifunctional Alcohols on Palladium Surfaces and Supported Catalysts
by
Michael Brandon Griffin
B.S., University of Florida, 2007

A thesis submitted to the
Faculty of the Graduate School of the
University of Colorado in partial fulfillment
of the requirement for the degree of
Doctor of Philosophy
Department of Chemical and Biological Engineering
2013
This thesis entitled:
The Reactivity of Multifunctional Alcohols on Palladium Surfaces and Supported Catalysts
written by Michael Brandon Griffin
has been approved for the Department of Chemical and Biological Engineering

J. Will Medlin

John L. Falconer

Date

The final copy of this thesis has been examined by the signatories, and we
find that both the content and the form meet acceptable presentation standards
of scholarly work in the above mentioned discipline.

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Griffin, Michael Brandon (Ph.D, Chemical and Biological Engineering)
The Reactivity of Multifunctional Alcohols on Palladium Surfaces and Supported Catalysts
Thesis directed by Associate Professor J. Will Medlin

In recent years there has been an increased interest in the development of sustainable
processes for the conversion of renewable resources into useful products. Among the most
promising of these is the upgrading of multifunctional alcohols with palladium catalysts. We
present here an investigation into the fundamental mechanistic details associated with the
conversion of these molecules as well as routes towards the development of improved
industrial catalysts.
Ethylene glycol (HOCH CH OH) and 1,2-propanediol (HOCH(CH )CH OH) are important
2 2 3 2
biorefining intermediates and serve as probe molecules for more complex polyols. By utilizing
surface science techniques we have gained molecular level insight into the interactions of these
molecules with a Pd(111) single crystal surface. The results show evidence that adjacent
functional groups on multifunctional alcohols can influence each other, leading to reactions
that are not observed from their simple alcohol analogues.
Studying 2-iodoethanol (ICH CH OH) provides insight into how the presence of halogen
2 2
catalyst modifiers affects the reactivity of multifunctional alcohols. In this investigation, iodine
was observed to influence the adsorption geometry and reaction selectivity of the hydroxyethyl
intermediate (-CH CH OH). In order to better understand this effect, 1-propanol
2 2
(CH CH CH OH) and 2-propanol (CH CH(OH)CH ) were studied on Pd(111) pre-covered with
3 2 2 3 3
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varying amounts of iodine. The results suggest that blocking active sites with strongly adsorbed
catalyst modifiers can have large effects on the reactivity of multifunctional alcohols.
The utilization of bimetallic catalysts is another way to influence reactivity. By studying
the oxidation of ethylene glycol and 1,2-propanediol on Pd/C, Au/C and Au-Pd/C we have
gained insight into bimetallic effects, which are associated with a significant increase in catalytic
activity. Experiments with isotopically labeled reagents show that C-H bond scission is the rate-
limiting step, and computational modeling suggested that an altered electronic structure may
be responsible for the increased catalytic performance.

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Acknowledgements
I'd like to first thank my advisor Will for his guidance on this project. His optimism and
encouragement made it easy to stay motivated. Will's thoughtfulness is matched only by his
patience, and his leadership abilities are something to which I will aspire for the rest of my
career. I would also like to thank the members of my committee: John Falconer, Dan Schwartz,
Rex Skodje, and Alan Weimer. Their knowledge and insight provided significant contributions to
the ideas presented in this thesis.
The work contained within these pages is due to the collective efforts of many
individuals. Erica Jorgensen and Sarah Daniels demonstrated extreme prowess with the UHV
systems and provided much of the data presented in the second chapter. The DFT studies
completed by Simon Pang and Matt Montemore provided a strong fundamental foundation for
the experimental investigations to build upon. The work presented in the fourth chapter would
not have been possible without Abraham Rodriguez, John Monnier, and Chris Williams, who
shared their expertise in catalyst synthesis and provided access to their facilities at the
University of South Carolina. Each person in the Medlin Research Group made coming to the
lab an enjoyable experience which goes a long way towards happiness and productivity. My
friends and family also deserve a lot of credit for their support. Special recognition goes to
Franny for always being willing to listen to my ideas and telling me when they were crazy.

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Finally, this work would not have been possible without our funding sources. The
surface science work was supported by the National Science Foundation (CBET grant #0828767)
and the Department of Education (GAANN fellowship). The reactor studies were funded in part
by a seed grant from the Colorado Center for Biorefining and Biofuels.

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Chapter 1: Introduction .................................................................................................................. 1

1.1 Biomass ................................................................................................................................. 1

1.2 Catalysis ................................................................................................................................. 2

1.3 Alcohol and Polyol Oxidation on Gold and Platinum-Group Metals .................................... 4

1.4 Description of Techniques ..................................................................................................... 9

1.5 Thesis Goals ........................................................................................................................ 12

1.6 Thesis Scope ........................................................................................................................ 13

1.7 References ........................................................................................................................... 15

Chapter 2: The Surface Chemistry of Ethylene Glycol and 1,2-Propanediol on Pd(111) ............ 21

2.1 Abstract ............................................................................................................................... 21

2.2 Background .......................................................................................................................... 21

2.3 Methods ............................................................................................................................. 23

2.4 Results ................................................................................................................................. 26

2.4.1 Ethylene Glycol TPD ...................................................................................................... 26

2.4.2 1,2-Propanediol TPD ..................................................................................................... 29

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2.4.3 Ethylene Glycol HREELS ................................................................................................ 33

2.4.4 1,2-Propanediol HREELS ............................................................................................... 36

2.5 Discussion ............................................................................................................................ 38

2.6 Conclusion ........................................................................................................................... 42

2.7 References ........................................................................................................................... 43

Chapter 3: The Surface Chemistry of 2-Iodoethanol on Pd(111) ................................................. 45

3.1 Abstract ............................................................................................................................... 45

3.2 Background .......................................................................................................................... 45

3.3 Methods .............................................................................................................................. 49

3.4 Results ................................................................................................................................. 52

3.4.1 2-Iodoethanol TPD ........................................................................................................ 52

3.4.2 2-Iodoethanol HREELS .................................................................................................. 56

3.4.3 2-Iodoethanol DFT ........................................................................................................ 61

3.4.4 1-Propanol TPD ............................................................................................................. 67

3.4.5 2-Propanol TPD ............................................................................................................. 69

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3.4.6 1-Propanol HREELS ....................................................................................................... 70

3.4.7 2-Propanol HREELS ....................................................................................................... 74

3.5 Discussion ............................................................................................................................ 77

3.5.1 2-Iodoethanol on Pd(111) ............................................................................................ 77

3.5.2 1-Propanol and 2-Propanol on I/Pd(111) ..................................................................... 80

3.6 Conclusion ........................................................................................................................... 82

3.7 References ........................................................................................................................... 83

Chapter 4: The Oxidation of Polyols on Pd/C, Au/C, and Pd-Au/C ............................................... 87

4.1 Abstract ............................................................................................................................... 87

4.2 Background .......................................................................................................................... 87

4.3 Methods ............................................................................................................................. 89

4.4 Results ................................................................................................................................ 95

4.4.1 Catalyst Preparation and Characterization .................................................................. 95

4.4.2 Ethylene Glycol Oxidation ............................................................................................ 98

4.4.3 1,2-Propanediol Oxidation.......................................................................................... 100

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