Catalysts are used in a wide variety of industrial applications to accelerate the rates of chemical transformations. Heterogeneous catalysts (e.g., zeolites, supported metals, and transition metal sulfides) are used in petroleum refining, chemical manufacturing, and pollution abatement. We are currently developing new highly efficient catalytic processes for converting bio-based fats and oils (triglycerides) into transportation fuels and converting byproduct glycerol into value-added chemicals, such as propanediols and glycerol carbonate. Biocatalysts (enzymes) are of vital importance in the production of transportation fuels from renewable resources. Bioethanol production in the US has expanded rapidly driven by high petroleum prices and government incentives for biomass-derived alternative fuels. Starch (from corn, wheat, barley, sweet potatoes, and other crops) and cellulosic biomass can be used as sources of sugars for fermentation to ethanol. We are currently working with industry to gain a better understanding of fuel ethanol production via simultaneous saccharification and fermentation of very-high-gravity corn mash using glucoamylase enzymes and yeast. This research is facilitated by applying in-situ near infrared spectroscopy, in-situ Raman spectroscopy and on-line mass spectrometry.
Catalytic reactions occur at specific active sites, e.g., gold nanoparticles on a metal oxide support or lattice defects on a metal oxide surface. Moreover, since catalysis is a dynamic phenomenon, the active site is often formed only under reaction conditions and changes in metal oxidation state and metal-ligand coordination occur during the catalytic cycle. Better fundamental understanding of heterogeneous catalysis should lead to improved catalysts for efficient, environmentally benign production of chemicals and fuels. In our basic catalysis research, we employ spectroscopic tools to elucidate the structure of the active site and identify key surface reaction intermediates. In-situ x-ray absorption spectroscopy and infrared spectroscopy are applied under steady-state and transient conditions to characterize conventional high-surface-area catalysts. We are also pursuing research on planar model catalysts prepared by depositing metal nanoparticles on metal oxide thin films. These model catalysts can be characterized using a variety of ultra-high-vacuum surface science techniques including Auger electron spectroscopy, temperature-programmed desorption, x-ray photoelectron spectroscopy, and supersonic molecular beam scattering.