PREPARATION OF PT/ALUMINA CATALYSTS BY THE SOL-GEL METHOD

A series of alumina-supported Pt catalysts were prepared by using the sol-gel method. The effect of the variables of preparation, the nature of solvent removal and pretreatment were investigated. The total surface area, pore size distributions, Pt dispersions, and catalytic reactivity were measured for the various samples. It was determined that a stoichiometric water/aluminum alkoxide molar ratio of 3.0 gave the sample with the highest surface area. These sol-gel samples were fairly active in the reactions of n-hexane and showed desirable selectivities. Xerogel samples were found to be superior in comparison to the corresponding aerogel samples as far as total surface area and metallic dispersions were concerned. Mixing of silica to the alumina (after a prehydrolysis step) to an extent of 5 wt%, in order to form a 1.0 Pt/(95% alumina-5% silica) mixed metal oxide sample, increased the sample total surface area and metallic dispersion by a small extent, in comparison to the 1.0 Pt/alumina sample. © 1993 Academic Press, Inc.