Interactions of Metal Clusters with Pore Walls

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ABSTRACT CTS-9525797 This is a fundamental study of the role of radius of curvative in an oxide pore in catalytic interactions. It has not been possible to study this effect systematically until now; the discovery of mesoporous aluminosilicate molecular sieves provides a means of preparing oxide supports with uniform pores of varying sizes. The interactions of small platinum clusters with the walls of mesoporous (1.5-2.5 nm) molecular sieves (MCM-41 materials) having silicon/aluminum ratios greater than 3 are investigated. The principal tools are solid-state nuclear magnetic resonance spectroscopy and X-ray absorption spectroscopy. Chemisorption, physical adsorption, small-angle X-ray diffraction, and infrared, ultraviolet, and visible spectroscopies are also used. Three catalytic test reactions are employed: n - hexane aromatization to probe for small-particle stabilization against sintering and coke deactivation; neopentane hydrogenolysis and isomerization as a probe of metal-support interactions; and competitive hydrogenation of benzene and toluene to observe effects on adsorption. Mesoporous molecular sieves offer a control of the surface environment not heretofore available. It has not yet been established that this control can be exploited for practical ends. This project will provide a basis for evaluating the possibilities. ***