One-pot synthesis of isobutyl toluene via combined acylation and hydrogenation over Pd–Beta zeolite

Abstract

The original one-pot synthesis of isobutyl toluene by simultaneous acylation of toluene with acetic anhydride and hydrogenation of the formed isopropyltolyl ketone over Pd–Beta zeolite is described. Zeolite Beta was chosen due to its high acidic activity in toluene acylation with isobutyric anhydride as well as after modification with Pd due to a high activity in hydrogenation of isopropylphenyl ketone to isobutyl benzene. The rate of the formation of isobutyl toluene substantially increases with the hydrophobicity of zeolite Beta despite the “simultaneous” or “consecutive” mode of the experimental setup applied. It is explained by the easier desorption of polar products and faster transport from acid sites to Pd particles, on which the primary formed ketone intermediate is hydrogenated. No effect of hydrogen pressure on the formation of isobutyl toluene was observed, however, with increasing hydrogen pressure hydrogenation of toluene, used as reactant as well as solvent, proceeds at a larger extent.