Introductory Remarks

As CO₂ emissions increase, efforts much be put forth to reduce the impact on climate change and ocean acidification. An interesting and attractive alternative approach would be the conversion of CO₂ into chemicals and fuels, which has been intensively pursued for renewable and sustainable energy.^[1] However, due to the negative adiabatic electron affinity and large ionization potential, the CO₂ molecule is chemically inert, thus making the conversion difficult under normal conditions. Heterogeneous catalysts, with high stability, superior efficiency and low cost are urgently needed to facilitate the problems concerning the processes of CO₂ conversion and utilization.

Research Experience:

My research career path has been a blend of many fields: chemical engineering, materials science and heterogeneous catalysis. My graduate research was devoted to the synthesis of the following high-surface area bimetallic catalysts for energy applications: Fe-Ce solid solution for hydrogen production via ethanol steam reforming^[2] and Cu-Cr catalysts for hydrogenolysis of glycerol.^[3-4] During my PhD study and postdoctoral training at the ETH Zurich, I focused on catalytic conversion of biomass to value-added chemicals over zeolite and zeolite-based catalysts.^[5-7] The catalysts were fully characterized by state-of-the-art techniques, including two-dimensional solid-state nuclear magnetic resonance spectroscopy (2D SS NMR), electron microscopy, X-ray absorption spectroscopy.^[8-10] The dual role of zeolites and zeolite-based catalysts was proposed via both stabilization of the intermediates and catalytic transformation of the intermediates to the desired products, e.g. aromatic hydrocarbons. We demonstrated that by choosing the proper transition metals, such as iron, and fine tuning the acidity and morphology of zeolites, the selectivity to the desired products was controllable.^[7] My current research at University of Rochester includes rationally designing and developing a fundamental understanding of highly active and selective zeolite-based catalysts for CO₂ hydrogenation into light olefins.

Successful Proposals:

1. Contributing author to an industry grant: Phenol and aromatics from lignin, funded by SABIC Americas, 2015-2017, Switzerland. (~ $400,000 for two years)
2. Contributing author to the National Research Program "Resource Wood" (NRP 66), funded by Swiss National Science Foundation, 2011-2013, Switzerland. (~ $200,000 for two years)

Future Research Directions:

As faculty member, I plan to continue my research on design and synthesis of novel catalysts for CO₂ conversion to chemicals and fuels. My vision is to combine the extensive knowledge obtained during my academic training: catalyst design, synthesis, characterization, and performance evaluation, to develop selective catalysts for reduction of carbon oxides. Iron catalysts, typically used for Fischer-Tropsch synthesis (FTS), have shown the greatest potential in converting CO₂ to value-added hydrocarbons;^[11] however, the selectivity to specific products, for example light olefins, is generally low. Zeolites, due to their unique structure and controllable morphology and acidity, have shown excellent activity, shape selectivity and stability for energy applications, e.g. biomass catalytic conversion to fuels and chemicals.^{[5-7, 9]} Therefore, the addition of zeolites to iron catalysts, to synthesize hybrid catalysts e.g. Fe-ZSM-5, is essential to fine tune the product distribution to the more desirable light olefins.

A second approach is to design a multifunctional catalyst that first converts CO₂ to CO, the main component in syngas; then CO (or syngas) is converted to hydrocarbons over the same catalyst via FTS. The design of such a multifunctional catalyst is extremely challenging because thermodynamics dictates that the conversion of CO₂ to CO is slightly endothermic and FTS is exothermic, which requires that the catalyst be operated under two different temperature regimes. The ideal catalyst should be composed of three components: 1) an active component for the conversion of CO₂ to CO; 2) a FTS catalyst that converts the produced CO to hydrocarbons; and 3) a component which controls the hydrocarbon selectivity. Although CO₂ is chemically inert, it could be converted into CO with high selectivity over transition metal carbides at relative low temperature, e.g. Molybdenum carbide (Mo₂C).^[12] For the FTS component, iron and transition metal oxides have showed promising performance,^[13-14] while zeolites can control the hydrocarbon selectivity. Therefore, a catalyst that combines Mo₂C, Fe, and a zeolite (Mo₂C/Fe/zeolite) could be an initial candidate. Upon further research studying the effect of varying each component, the knowledge gained will provide fundamental understanding of desirable catalysts of CO₂ conversion to chemicals and fuels.

Teaching Interests:

Courses that I would be interested in teaching are an introductory course in chemical engineering principles and surface science. The introductory course could be heat and mass transfer or catalytic reaction engineering; and the surface science course covers the different characterization techniques used in heterogeneous catalysis, from basic principles to applications. I have taught the chemical engineering laboratory course at the undergraduate and graduate level, and the surface science course as a teaching assistant to graduate students. Through my participation as a teaching assistant, I have developed confidence and an interest in teaching and look forward to the opportunity to both teach assigned classes and develop my own classes in chemical engineering. And lastly, I have extensive experience mentoring graduate students in my group during my doctoral and postdoctoral research (1 PhD, 2 third-year PhD candidates, 5 master students).

References:

1. Kondratenko, E. V.; Mul, G.; Baltrusaitis, J.; Larrazabal, G. O.; Perez-Ramirez, J., Status and perspectives of CO2 conversion into fuels and chemicals by catalytic, photocatalytic and electrocatalytic processes. Energy Environ. Sci. 2013, 6 (11), 3112-3135.
2. Ma, Z.; Xiao, Z.; van Bokhoven, J. A.; Liang, C., A non-alkoxide sol–gel route to highly active and selective Cu-Cr catalysts for glycerol conversion. J. Mater. Chem. 2010, 20, 755-760.
3. Liang, C.; Ma, Z.; Lin, H.; Ding, L.; Qiu, J.; Frandsen, W.; Su, D., Template preparation of nanoscale CexFe1-xO2 solid solutions and their catalytic properties for ethanol steam reforming. J. Mater. Chem. 2009, 19 (10), 1417-1424.
4. Liang, C.; Ma, Z.; Ding, L.; Qiu, J., Template Preparation of Highly Active and Selective Cu–Cr Catalysts with High Surface Area for Glycerol Hydrogenolysis. Catal. Lett. 2009, 130, 169-176.
5. Ma, Z.; Troussard, E.; van Bokhoven, J. A., Controlling the selectivity to chemicals from lignin via catalytic fast pyrolysis. Appl. Catal., A. 2012, 423–424 (0), 130-136.
6. Ma, Z.; Ghosh, A.; Asthana, N.; van Bokhoven, J., Optimization of the Reaction Conditions for Catalytic Fast Pyrolysis of Pretreated Lignin over Zeolite for the Production of Phenol. ChemCatChem 2017, 9 (6), 954-961.
7. Ma, Z.; Custodis, V.; van Bokhoven, J. A., Selective deoxygenation of lignin during catalytic fast pyrolysis. Catal. Sci. Technol. 2014, 4 (3), 766-772.
8. Li, T.; Ma, Z.; Krumeich, F.; Knorpp, A. J.; Pinar, A. B.; van Bokhoven, J. A., Properties modification of nano-sized hollow zeolite crystals by desilication. ChemNanoMat 2018, doi: 10.1002/cnma.201800225.
9. Ma, Z.; Ghosh, A.; Asthana, N.; van Bokhoven, J., Visualization of structural changes during deactivation and regeneration of FAU zeolite for catalytic fast pyrolysis of lignin using NMR and electron microscopy techniques. ChemCatChem 2018, doi: 10.1002/cctc.201800670.
10. Ma, Z.; van Bokhoven, J. A., Deactivation and Regeneration of H-USY Zeolite during Lignin Catalytic Fast Pyrolysis. ChemCatChem 2012, 4 (12), 2036-2044.
11. Abelló, S.; Montané, D., Exploring Iron-based Multifunctional Catalysts for Fischer–Tropsch Synthesis: A Review. ChemSusChem 2011, 4 (11), 1538-1556.
12. Porosoff, M. D.; Yang, X.; Boscoboinik, J. A.; Chen, J. G., Molybdenum Carbide as Alternative Catalysts to Precious Metals for Highly Selective Reduction of CO2 to CO. Angew. Chem. Int. Ed. 2014, 126 (26), 6823-6827.
13. Jiao, F.; Li, J.; Pan, X.; Xiao, J.; Li, H.; Ma, H.; Wei, M.; Pan, Y.; Zhou, Z.; Li, M.; Miao, S.; Li, J.; Zhu, Y.; Xiao, D.; He, T.; Yang, J.; Qi, F.; Fu, Q.; Bao, X., Selective conversion of syngas to light olefins. Science 2016, 351 (6277), 1065-1068.
14. Torres Galvis, H. M.; Bitter, J. H.; Khare, C. B.; Ruitenbeek, M.; Dugulan, A. I.; de Jong, K. P., Supported Iron Nanoparticles as Catalysts for Sustainable Production of Lower Olefins. Science 2012, 335 (6070), 835-838.