Reactions of hydrocarbons on alumina-supported Pt–Ir bimetallic catalysts. Part 2.—Exchange of benzene with deuterium, and exchange and hydrogenolysis of 2,2-dimethylpropane

Abstract

Exchange reactions of benzene at 263 K and the exchange an hydrogenolysis of 2,2-dimethylpropane at a range of temperatures have been studied over a series of alumina-supported Pt–Ir catalysts. Neither the rate nor the character of the exchange reactions varied greatly with metal composition. The rates of hydrogenolysis of 2,2-dimethylpropane increased markedly with iridium content, and the shapes of the activity–composition curves were interpreted in terms of active sites consisting of ensembles of four metal atoms. Mixed metal ensembles had an activity intermediate between those of the pure metals. The present results, together with those from the preceding paper, show that, for all hydrocarbons, the depth of hydrogenolysis increased with iridium content, probably owing to a rising strength of adsorption. With platinum, similar types of C—C bonds in different hydrocarbons underwent cleavage at similar rates; secondary–secondary bonds were most easily broken and primary–quaternary were the least reactive.