PROPOSAL NUMBER: 0731074 PRINCIPAL INVESTIGATOR: Williams, Chris INSTITUTION: University of South Carolina
The goal of this proposed research is to develop an understanding of the surface chemistry that governs asymmetric C=C bond hydrogenation in a,B-unsaturated acids over cinchona alkaloid-modified metal catalysts. In contrast to the exhaustively studied alpha-activated C=O hydrogenation reactions over these catalysts, hydrogenation of a,B-unsaturated acids has been much less well studied from both a kinetic and surface science standpoint. A combination of attenuated total reflection infrared spectroscopy (ATR-IRS), surface-enhanced Raman spectroscopy (SERS), and sum frequency spectroscopy (SFS), will be used which are in-situ vibrational approaches the PI has applied successfully to solid-liquid catalytic interfaces over the past several years. So far, the majority of in-situ spectroscopic studies of these catalysts that have been performed (including by the PI) have focused almost entirely on the cinchona alkaloid modifier interaction with the catalyst surface under different conditions. The research will therefore build upon this foundation by focusing more on the adsorption of reactants and products, and their co-adsorption with the modifier. Most important, a major component of the studies will involve spectroscopic measurements under a range of reaction conditions (i.e., various solvents, temperatures and H2 pressures) while simultaneously detecting liquid-phase concentrations of reactants and products. Such an-operando spectroscopi-approach will allow for direct correlations to be made between the time dependent surface speciation and catalytic rates/selectivity.
This research will provide a comprehensive investigation of one of the most important heterogeneous chiral catalytic systems. The in-situ/operando spectroscopic studies will fill a notable void in the literature, given that there are so few studies of cinchonidine-modified metal surfaces under true reaction conditions. The findings should provide increased understanding of the mechanism of a,B-unsaturated acid hydrogenation, which in turn might lead to development of new and more effective catalysts. More generally, the further development and establishment of the in-situ/operando vibrational spectroscopic methods described here will also have a notable impact on the study of other important solid-liquid catalytic systems.
Two PhD students will be educated through the research, and become experts in state-of-the-art spectroscopic and kinetic characterization of catalysts. Graduate students from underrepresented groups will be attracted through the ongoing Sloan Minority Graduate Fellowship and Southeast Alliance for Graduate Education and the Professoriate (SEAGEP) programs that are available in Chemical Engineering at USC. At the undergraduate level, an NSF-REU site focusing on Green Chemistry in Chemical Engineering is presently operating at USC. Given the environmental benefits that can be realized through use of heterogeneous catalysts for enantioselective synthesis, the work fits in well with this program. Funding will help to provide meaningful short-term projects for two of these students every year in the area of heterogeneous enantioselective catalysis and surface spectroscopy.
