Exchange reactions of benzene, toluene, and m-xylene with deuterium on silica–alumina and alumina catalysts

Abstract

The exchange reactions of benzene, toluene, and m-xylene with deuterium have been studied on two silica–alumina catalysts containing 13%(I) or 45%(II) alumina and on pure alumina. The temperature ranges studied were 125–440°, 20–100°, and 20–250° for the three catalysts respectively. On any catalyst the hydrogen atoms in the ring positions of all three hydrocarbons reacted at the same rate and there were no appreciable directing effects due to the side-groups. Rates of reaction were substantially lower on silica–alumina I than on the other catalysts. Side-group exchange with toluene or m-xylene was slower than ring exchange by factors ranging from 30 upwards. Subsidiary experiments on hydrogen–deuterium exchange and on the isomerization of m-xylene were also carried out. Silica–alumina I was the least active for hydrogen–deuterium exchange and isomerized m-xylene at rates comparable with those found for side-group exchange.