Bronstedd and Lewis solid superacids of carrier/metal halide type

Superacid properties of alumina, silica-alumina and silica exposed to TiCl4 and HfCl4 vapour have been studied and compared with previously obtained results for catalysts containing BF3, SbF3, AlCl3 and ZrCl4. It was found that the reaction of the vapour of metal halides of Lewis nature (MeXn) with oxides like alumina, silica-aluminas and silica results in the formation of the Bronsted superacid centers if acid strength of hypothetical acid MeXn×XH is higher than that of sulphuric one. The Lewis superacid centers are formed in the reaction of carrier containing alumina phase with metal halide of strong electron acceptor ability.