(6ca) Catalysis for Sustainability: Probing the Fundamentals of Chemical Conversion Using Synthetic, Kinetic, and Electrocatalytic Approaches

Research Interests: The petrochemical and energy industries are currently tethered to carbon-based feedstocks for the foreseeable future in the transition towards reaching sustainable, carbon-neutral solutions. Chemical conversion is facilitated and enhanced through the use of both electrocatalytic and thermocatalytic processes, and sources of renewable-derived electrical energy will be critical to the future of these processes. In the medium-term, there is a crucial demand for the development and improvement of technologies for fuel and chemical production from carbon-based feedstocks including natural gas and biomass, and reduction of the global carbon footprint needs to be pursued via CO₂ conversion technologies. My research aims to fundamentally understand and optimize electrochemical and thermocatalytic petrochemical conversion pathways as a means to facilitate the transition from fossil fuel dependence towards a sustainable future founded upon efficient, electrocatalytic conversion methods. My research aims to understand how catalysts function in order to develop novel processes and to improve upon existing methods of chemical conversion for a sustainable future, specifically with regards to the utilization of electrochemical energy, natural gas, and CO₂.

Postdoctoral Projects: Catalytic partial oxidation of methane to methanol over metal-exchanged zeolite catalysts, and Non-Faradaic electrochemical promotion of catalytic alkane oxidation and CO₂ reduction, Department of Chemical Engineering, Massachusetts Institute of Technology. (Adviser: Associate Professor Yuriy Román-Leshkov).

PhD Dissertation: Evolution in structure and function of transition metal carbides during the catalytic activation of C-O, C-H, and C-C bonds, Department of Chemical Engineering and Materials Science, University of Minnesota-Twin Cities. (Adviser: Associate Professor Aditya Bhan).

Research Experience: During my PhD, I focused on the study of transition metal carbides as catalysts for biomass hydrodeoxygenation and alkane oxidative dehydrogenation. Specifically, my research prioritized the use of kinetic characterization and active site titration techniques as tools to quantify and comprehend the dynamic nature of the working catalyst in situ. Using site-specific titrations, I was able to manipulate and measure the number of active acid sites in situ, directly attributing co-feed induced changes in reaction rate to site density alterations [1,4]. I also developed detailed kinetic models of propane oxidative dehydrogenation reactions using CO₂ to transiently model the changing nature of the catalyst surface as a function of extent of oxidation, and this model could directly describe changes in dehydrogenation, hydrogenolysis, and reverse water-gas-shift reactions [2]. During my postdoctoral research, I focused upon learning how to incorporate electrochemical techniques into catalytic systems, specifically non-Faradaic electrochemical promotion of catalysis (EPOC or NEMCA), and I learned catalyst synthesis methods to direct active site speciation. I also gained experience with in situ x-ray absorption spectroscopy as an additional technique to identify the nature and local environment of the active site in the working catalyst. In order to characterize catalysts both in situ and ex situ, I have experience using X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, liquid nitrogen physisorption, and chemisorption techniques. I have also worked closely with collaborators on transmission electron microscopy and X-ray photoelectron spectroscopy.

Future Research Directions: As a principal investigator, my philosophy is that a catalyst is best understood when we watch it work; in situ and operando kinetic and spectroscopic characterizations are at the heart of fundamental catalysis science, and the incorporation of electrical energy into catalytic systems offers enormous potential. This philosophy will be applied to petrochemical conversion of carbon-based feedstocks, specifically CH₄ and CO₂, via thermochemical and electrocatalytic pathways using selective catalyst synthesis methods. The Sullivan lab will pursue these goals by three interrelated avenues: (i) the incorporation of in situ electrochemical catalytic modification as a method of tuning reaction energetics and modifying rates and selectivity, (ii) targeted catalyst synthesis for the purpose of optimizing active site density, speciation, and local environment, and (ii) detailed kinetic and mechanistic studies of catalytic reactions in order to probe active site requirements and chemical conversion pathways. This work will incorporate the kinetic and mechanistic investigative tools I gained from my PhD as well as the electrochemical and synthetic techniques I learned during my postdoctoral research.

Teaching Experience: In my time at the University of Minnesota, I was a teaching assistant (TA) for three semesters of classes: (i) one undergraduate class (Mass Transport and Separations Processes, CHEN 3006), (ii) one graduate class (Physical Rate Processes, CHEN 8301), and (iii) one semester as a recitation instructor for two separate sections of ~25 undergraduate students that I taught twice a week (Reaction Kinetics and Reactor Engineering, CHEN 3102). I was awarded the Outstanding TA Award for my work with both CHEN 3102 and CHEN 8301 while working with graduate students and while working as a recitation instructor. Serving as a recitation instructor for CHEN 3102 afforded me the opportunity to work with the lead professor in order to plan recitation lectures, to write homework and exam problems, and to gain feedback from the undergraduate students. I lectured the entire class of ~130 students on multiple occasions when filling in for the lead instructor both by using his notes and by writing my own lecture from scratch, and I also filled in as an instructor for lectures of CHEN 3102 the following year when I was not a recitation instructor for the class. I also had the privilege of training and working with two undergraduate researchers from the University of Minnesota as well as a visiting foreign graduate student who worked in the Bhan lab for one summer.

Teaching Interests: I prefer to teach courses pertinent to the fundamentals of chemical engineering. Specifically, I am interested in teaching classes related to catalysis and reaction engineering, heat and mass transport, fluid mechanics, thermodynamics, mass and energy balances, or mathematics relevant to chemical engineering.

Selected Publications:

1. M. Sullivan, J.T. Held, A. Bhan, “Structure and site evolution of molybdenum carbide catalysts upon exposure to oxygen.” Journal of Catalysis, 326, 82-91 (2015).
2. M. Sullivan, A. Bhan, “Effects of oxygen coverage on rates and selectivity of propane-CO₂ reactions on molybdenum carbide.” Journal of Catalysis, 357, 195-205 (2018).
3. M. Sullivan, C.-J. Chen, A. Bhan, “Catalytic deoxygenation on transition metal carbide catalysts.” Catalysis Science & Technology, 6 (3), 602-616 (2016).
4. M. Sullivan, A. Bhan, “Acid site densities and reactivity of oxygen-modified transition metal carbide catalysts.” Journal of Catalysis, 344, 53-58 (2016).
5. M. Sullivan, A. Bhan, “Acetone hydrodeoxygenation over bifunctional metallic-acidic molybdenum carbide catalysts.” ACS Catalysis, 6 (2), 1145-1152 (2016).
6. T. Dinh*, M.M. Sullivan*, M. Dinca, Y. Román-Leshkov, “A viewpoint on partial oxidation of methane to methanol using Cu- and Fe-exchanged zeolites.” In revision, (2018). (*co-first)