Long-Term Research Visit to Japan: Electronic Properties and Catalytic Activity of Supported Metal Oxides

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9819369OyamaThis award provides funds to support a 12-month research visit by Dr. S. Ted Oyama, Department of Chemical Engineering, Virginia Polytechnic Institute and State University, for collaboration with Drs. Yasuhiro Iwasawa and Kiyotaka Asakura, Department of Chemistry, University of Tokyo, and Dr. Kazunori Domen, Research Laboratory of Resources Utilization, Tokyo Institute of Technology, Japan. These collaborators will conduct investigations on the reactivity of oxide catalysts. The project involves examining the relationship between electronic structure and catalytic activity of oxide surfaces. Preliminary work indicates that in alcohol oxidation reactions there is a strong effect of supporting oxides of the catalysts that results in orders-of-magnitude difference in turnover rate, with little effect on the activation energy. This can be explained by a rate-determining step that involves electron transfer to the catalytic site. Thus, an important requirement for an effective catalyst is for it to have accessible electronic levels to accept electrons. This is reasonable because oxidation involves loss of electrons by the reactants. The principal objective of this study is to investigate the electronic structure of working catalysts to ascertain that the availability of electron-accepting levels is related to the catalytic activity. This will be done by carrying out in situ XANE~S (x-ray absorption near edge spectroscopy), which probes the electronic levels above the Fermi energy. These measurements will be supported by EXAFS (extended x-ray absorption fine structure) data to provide the structure of the catalysts, an important requirement for interpreting the XANES results. In addition, in situ infrared measurements will be carried out to check that the structure of the reactive intermediates is the same on all supported catalysts.The systems to be studied are two series of molybdenum and manganese catalysts supported on SiO2, Al203, TiO2, and ZrO2, and will be employed in the oxidation of ethanol. These catalysts are ideal for the investigation because they are, respectively, partial and total oxidation catalysts. Thus, their use will also allow study of the relationship of selectivity to catalytic activity. This research is significant because it will yield fundamental information about the factors that control catalytic activity in oxidation systems. The information can be extended to many other reactions in which electron transfer processes are important, and also can be applied to catalyst design. The investigation will provide the PI with training in an important scientific technique, the use of synchrotron radiation. It also is expected that the interaction will lead to the exchange of students between the U.S. and Japan. The collaboration will be mutually beneficial because of the complementary expertise of the collaborators which will contribute to the two-way exchanges of ideas, skills, and techniques.***