EAGER: Catalysis Fundamentals of Selective Hydrogenation of Aromatic Hydrocarbons

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Catalysts speed up chemical reactions while promoting the selective conversion of feedstocks to desired products. Cyclic olefin compounds are a class of chemical compounds that are used widely in the chemical, pharmaceutical, and food industries. Their current manufacture, however, relies on inefficient catalysts and multistep processes that produce unwanted by-products, including hazardous and environmentally-unfriendly chemicals. Moreover, current feedstocks primarily consist of aromatic hydrocarbons derived from fossil sources. The project addresses the need for better fundamental understanding of the catalytic chemistry associated with cycloolefin manufacture. The fundamental insights will support development of models capable of predicting catalyst formulations and process conditions tuned to produce high yields of targeted products in energy-efficient single-step reactions. The models will be extended to biomass and other renewable feedstocks to enhance green chemistry and energy sustainability. Fundamental relationships between the structure of transition-metal catalysts and reactivity of aromatic hydrocarbons will be established at the molecular level via an integrated experimental-theoretical study focusing on single-step selective hydrogenation of hydrocarbons (containing one aromatic ring) to cycloolefins. Selective hydrogenation of tetralin to octalin will be used as a model reaction. Initial experiments will focus on previously identified promising catalysts consisting of supported Pd-Pt and Ni-Sn nanoparticles. Additional catalyst formulations will be selected based on the initial results. Experimental studies will provide information for the development of calibrated molecular models, which in turn will provide a better interpretation of the experimental results, and guide the selection of follow-up experiments to further improve the models in an iterative cycle. The study will synergistically and iteratively combine: (1) kinetic reaction measurements at steady-state and transient conditions, (2) in situ Raman and infrared vibrational spectroscopic measurements and (3) quantum-chemical calculations for interpretation of vibrational spectra, and transition state calculations for identification of reaction mechanisms. Elements of reaction engineering will be incorporated through kinetic models developed from data obtained over a range of temperature, reactant partial pressure, and reaction-time data. In addition to the technical aspects, the project will enable students to master critical skills needed to compete and contribute successfully in the international economy of the 21st century, particularly in the vital fields of sustainable chemical production and nanotechnology. The research team will also support undergraduate and K-12 educational outreach programs at the investigator’s institution.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.