Solid Superacid Catalysts Based on Tungsten Oxide

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ABSTRACT CTS-9510575 This joint effort between the University of California at Berkeley, Exxon Corporation and the Metropolitan Autonomous University at Iztapalapa, Mexico, involves the synthesis and characterization of solid "superacids" based on tungsten oxide dispersed as isolated species, clusters, or films on the surface of zirconia or titania. Previous work has shown that tungsten oxide on zirconia has catalytic activity for isomerization of higher alkanes without the cracking caused by other "superacids". In order to improve the catalytic activity, higher surface areas are desirable. This work includes detailed study of the solid-state processes involved in the precipitation of high-surface-area zirconium and titanium oxides and in the dispersion of tungstate groups on their surfaces. Structural studies are performed using X-ray diffraction and absorption techniques, electron microscopy, and infrared and Raman spectroscopies; acid-site densities and chemistry are probed using site titrations and catalytic reactions of propylene and dimethylcyclohexane. These studies are complemented with mechanistic studies using in-situ infrared spectroscopy and isotope jump techniques. Branched alkanes have great value as octane enhancers in gasoline, lubricant components, and chemical feedstocks. Traditionally, these have been made using one of several processes employing liquid acids, but it is generally accepted that these processes will soon be replaced by new processes using solid acids. Among the advantages sought in this move are easier containment, less corrosiveness, environmental benignity, and improved selectivity. This effort is supported jointly by the Chemical Reaction Processes Program (CTS), the Solid State Chemistry and Polymers Program (DMR), and the Americans Program (INT). ***