RING ENLARGEMENT AND AROMATIZATION OF PROPYLCYCLOBUTANE OVER SILICA-SUPPORTED PT, PD AND RH IN HYDROGEN ATMOSPHERE

Ring enlargement and/or aromatization accompany the hydrogenative ring opening of propylcyclobutane over Pt/SiO2, Rh/SiO2 and Pd/SiO2 cataly sts at high temperature. Ring enlargement provides only methylcyclohex ane, while toluene and benzene are the products of aromatization. Both reactions occur over Pt/SiO2, whereas only aromatization takes place over the other two catalysts. Increasing hydrogen pressure favours dir ect methylcyclohexane formation, while under relatively hydrogen-poor conditions it forms via secondary pathways. Benzene formation is favou red by temperature increase and is probably due to the demethylation o f adsorbed toluene-like species.