PYROLYSIS AND SPECTROSCOPY OF CYCLIC AROMATIC COMBUSTION INTERMEDIATES by ...

346 Pages·2016·40.28 MB·English

by  Buckingham, Grant

PYROLYSIS AND SPECTROSCOPY
OF CYCLIC AROMATIC COMBUSTION INTERMEDIATES
by
GRANT THORNTON BUCKINGHAM
B.A. Carleton College 2010

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 Chemistry and Biochemistry
2016
This thesis entitled:
Pyrolysis and Spectroscopy of Cyclic Aromatic Combustion Intermediates
written by Grant Thornton Buckingham
has been approved for the Program of Chemical Physics

_________________________________
G. Barney Ellison

__________________________________
Veronica M. Bierbaum

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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Buckingham, Grant Thornton (Ph.D., Chemical Physics)
Pyrolysis and Spectroscopy of Cyclic Aromatic Combustion Intermediates
Thesis Directed by Emeritus Professor G. Barney Ellison

We have studied the pyrolysis of aromatic combustion intermediates using
an array of detection techniques. The molecules investigated include cyclic
aromatic molecules with hydrocarbon substituents (ethylbenzene, n-
propylbenzene, isopropylbenzene, and styrene), oxygen-containing substituents
(anisole and phenol), triply substituted systems (vanillin), resonance stabilized
radicals (benzyl radical and tropyl radical) and phenyl radical. At the exit of a
resistively heated micro-reactor (1 mm inner diameter, 3 cm long), the pyrolysis
fragments are detected using photoionization mass spectrometry (PIMS), matrix
isolation vibrational spectroscopy, microwave spectroscopy, tunable VUV
synchrotron-based PIMS, and table-top VUV PIMS with photoelectron photoion
coincidence spectroscopy (PEPICO). This array of detection methods allows for the
identification of all possible fragments including metastables, radicals, and atoms.
The findings allow for detailed mechanistic information regarding which pathways
are active at different pyrolysis temperatures. The findings can also be used to help
identify products and individual isomers that are formed during the gas-phase
thermal decomposition of aromatic systems. By providing direct experimental
pyrolysis data, models for fuel decomposition and soot formation can be improved
to help understand current combustion systems and eventually aid in the design of
superior fuel sources in the near future.

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ACKNOWLEDGMENTS

I think that I am on the verge of concluding one of the luckiest graduate school
experiences possible. The amount that I learned about chemistry, physics, and science
in general is fantastic but the 6 years I had in Boulder may be some of the most
important years of my life. I arrived in Colorado as a young, ignorant, insecure, and
poorly defined person and I write this now as a confidant self-sufficient, and driven
man. For this I am deeply indebted to 1) my family, 2) to my two research advisors,
David Nesbitt and Barney Ellison, and 3) to the group of friends I found in Boulder. My
advisors taught me about chemical physics and life as a scientist but the other two
camps helped me find who I am. To all three groups I am eternally grateful.
For the first two-and-a-half years of my degree, I worked with David Nesbitt,
who may be the most careful and creative thinker and teacher I have ever met. The
completeness of his understanding is truly staggering and the vigor with which he
pursues knowledge is something I will always strive to emulate. For the next 3.5 years I
worked with Barney Ellison learning a very different type of chemistry. Barney’s ability
to find and solve interesting problems, as well as amass a wonderful group of
colleagues and friends to help him do it showed me how great science can really be.
Working with him and learning to navigate academia has been more fun than I thought
graduate school could be. The combination of these two mentors has allowed me to
gain such a wealth (and breadth) of knowledge that I can’t imagine a more rewarding
Ph.D. experience.
It has been a pleasure working with so many fun and intelligent people during
my time here. In the Nesbitt group, I benefitted from knowing Melanie Roberts, Chih-
Hsuan Chang, Rob Roscioli, Kevin Early, Nick Dupuis, Mia Zutz, Andy Gisler, Mike
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Ziemkiewicz, Andrej Grubisic, Monika Gruetter-Kasumaj, Dan Nelson, Eric
Holmstrom, Tom Baker, and Julie Fiore and all of the JILA staff. In the Ellison group I
enjoyed working with Kimberly Urness, Jessie Porterfield, Josh Baraban, Tom Ormond,
Jong Kim, Fiona Deguillaume, John Stanton, John Daily, Qi Guan, Don David, the Ion
Super Group, Ronnie Bierbaum, Carl Lineberger, and Mathias Weber. I also had the
pleasure or collaborating with Mark Nimlos and David Robichaud at NREL; Tim Zwier
and his very welcoming group at Purdue University; the ALS team at Berkeley: Musa
Ahmed, Tyler Troy, and Oleg Kostko; Mike McCarthy and Marie-Aline Martin at
Harvard CfA; Hans-Heinrich Carstensen from the University of Gent; Bill Peters and
David Couch from the KM group; and Bryan Changala and Ben Spaun of Jun Ye’s
group.
I also need to acknowledge the tremendous experience I had at Carleton College,
where I learned about chemistry but also learned to love learning. The education I
received from the faculty there, especially Will Hollingsworth and Marion Cass, helped
me to succeed in graduate school but also showed me how to be passionate about
science.
The people I spend my free time with were hugely important to my time in
Boulder. My housemates at Armer: Jordan “Jo’j” Mirocha, Anthony Harness, Marek
Slipski, Emily Kraus, and Tristan Weber were always there for me to make me laugh.
Book Club with Eric Coughlin helped keep my life in balanced and coffee with Greg
Salveson helped keep my awake. Mia Zutz, Andy Gisler and Nick Dupuis were my
constant ski team and dinner crew. Galen Gorski, Kevin Early, Kevin Pollock, Matt
Nock, and Austin Hall were all there for me from a distance.
Finally, and most importantly, I want to acknowledge everything that my family
has done for me along the way. The unwavering support from my parents Kim
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Thornton and Kent Buckingham and sister Katherine Buckingham allowed me to
persevere and thrive during this stage of my life, and all the stages that preceded it.
There is no doubt that all of my strengths as a person came from being lucky enough to
be born into the family that I was.

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CONTENTS

Chapter 1. Introduction
I. Motivation 1
II. Understanding Current Combustion Systems 2
III. Selecting Better Future Fuels 7
IV. Outline 11
References for Chapter 1 14

Chapter 2. Experimental Methods
I. Introductions 17
II. High Resolution Absorption Spectroscopy 18
A. Difference Frequency Infrared Production 18
B. Slit Discharge Radical and Ion Production 19
III. Pyrolysis of Gas-Phase Biofuel Intermediates Using a Heated Micro-
Reactor 22

A. Pyrolysis in a heated Micro-Reactor 23
B. Photoionization Mass Spectroscopy 27
i. Photoionization Mass Spectrometry Using the 9th harmonic
of an NdLYAG Laser and Reflectron Time-of-Flight
Detection 28

ii. Photoionization Mass Spectrometry Using Synchrotron
Radiation and Time-of-Flight Reflectron Detection 29

iii. Photoionization Mass Spectrometry Using Synchrotron
Radiation and Imaging Photoelectron Photoion
Coincidence Spectroscopy 30

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iv. Photoionization Mass Spectrometry Using a Tabletop
Vacuum Ultraviolet Laser and Photoelectron Photoion
Coincidence Spectroscopy 32

C. Matrix Isolation Infrared Absorption Spectroscopy 35
D. Sample Preparation 36
References for Chapter 2 39

Chapter 3. High-Resolution Rovibrational Spectroscopy of Jet-Cooled Phenyl
Radical: The !19 Out-of-Phase Symmetric CH Stretch
Abstract 43
I. Introduction 44
II. Experimental 50
III. Results and Analysis 53
IV. Discussion
A. Nuclear Spin Weights 62
B. Planarity and In-Plane Ring Distortion 64
C. Intramolecular Vibrational Redistribution 69
V. Summary and Conclusions 75
References for Chapter 3 76

Chapter 4. Observation of the a CH Stretching Modes in Phenyl Radical using Jet-
1
Cooled Sub-Doppler Absorption Spectroscopy
Abstract 83
I. Introduction 83
II. Experimental 88
III. Results and Discussion
A. Spectral Observation and Analysis 89
B. Intensity Analysis 99
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IV. Summary and Conclusions 103
References for Chapter 4 104

Chapter 5. Hydropyrolysis of Ethylbenzene in a Heated Micro-Reactor
Abstract 107
I. Introduction 107
II. Experimental 112
III. Results and Discussion
A. Ethylbenzene Decomposition 113
B. Hydropyrolysis of Ethylbenzene 116
IV. Conclusions 125
References for Chapter 5 127

Chapter 6. The Thermal Decomposition of the Benzyl Radical in a Heated Micro-
Reactor: I. Experimental Findings
Abstract 131
I. Introduction 132
II. Experimental 139
III. Results 144
A. Decomposition of Benzyl-d Radical 145
0
B. Decomposition of Benzyl-d Radical 155
2
C. Decomposition of Benzyl-d Radical 160
5
D. Decomposition of 13C-Benzyl Radical, C H 13CH 161
6 5 2
IV. Discussion and Conclusions 167
References for Chapter 6 171

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Chapter 7. The Thermal Decomposition of the Benzyl Radical in a Heated Micro-
Reactor: II. Pyrolysis of the Tropyl Radical
Abstract 179
I. Introduction 180
II. Experimental
A. Heated Micro-Reactor Pyrolysis Source 185
B. Photoionization Mass Spectrometry
i. Pulsed Vacuum Ultraviolet Radiation 186
ii. Continuous Vacuum Ultraviolet Radiation 187
C. Matrix Isolation Fourier Transform Infrared Spectroscopy 187
D. Sample Preparation 188
III. Results and Discussion
A. Photoionization Mass Spectrometry 190
B. Matrix Isolation Spectroscopy 200
C. Cycloheptatrienyl or Norbornadiene as Tropyl Precursors? 205
IV. Conclusions 213
A. Pyrolysis of Benzyl Radical without Tropyl 214
References for Chapter 7 224

Chapter 8. Tabletop Vacuum Ultraviolet Laser-Based Photoionization Mass
Spectrometry with Photoelectron Photoion Coincidence Detection of Pyrolysis
Products
Abstract 233
I. Introduction 233
II. Experimental 237
III. Results and Discussion
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