Study on the Structure of Catalitic Acitve Sites by Means of Probe Reaction

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It has been required to develop more active and selective catalysts in these days, to solve the problems on the energy shortage and environmental pollution in the global scale. For this purpose, it is necessary to clarify the factors which control the catalytic activity and selectivity on the solid surface. Because of the remarkable progress on the surface analytic techniques, it is possible to define the surface structures of various catalysts. Accordingly, we applied the isotopic probe reaction method of propene-deuterium exchange process on the catalysts whose surface properties were modified systematically, and investigated the dependencies of the structure of reaction intermediates upon the modified surface properties by means of microwave spectroscopy.We have studied the structure sensitivity of the supported oxide catalysts by applying this method on ZrO_2, TiO_2 and ZnO catalysts highly dispersed on silica and alumina supports. It was demonstrated that several ten A oxide particles exhibit completely different catalytic behavior from larger oxide particles. We also have studied the structure of active sites of alumina supported Rh carbonyl cluster complexes and found that one or two surface Rh atoms are enough to catalyze this reaction. We also applied this method on the more complex reactions like oxidation, hydroformylation and NO reduction with propene and obtained interesting information on the controlling factors of the selectivity of these reactions.