Dealkylation of isopropylbenzene on 7-lrradiated silíca-alumina. The effect of various reagents on the active centers and on their yield

Abstract

A silica-alumina gel was exposed to a gaseous reagent during or after y irradiation, and the yield of benzene (molecules formed per gram of solid) on subsequent exposure to isopropylbenzene was determinad. The following reagents were used: Na, H2, O2, CO2, N2Ó, C2H4, NH3, H2S, CO, and SO2. In general, effects of the reagents on the benzene yield correlate with previously reported effects of the same reagents (for corresponding conditions) on the positive-hole esr spectrum of the irradiated silica-alumina. The esr spectrum includes contributions from a positive hole trapped on a bridging oxygen atom bonded to a substitutional Al atom and from certain positive holes trapped on nonbridging oxygen. Certain of the results indícate that the yield of benzene from contact of isopropylbenzene with silica-alumina irradiated alone, like the yield of trapped positive holes seen in the esr spectrum, is limited by the number of preexisting electrón traps in the silica-alumina matrix, The total results seem to require that electrón transfer from isopropylbenzene to a trapped positive hole (of any kind contributing to the esr spectrum).