Superacidity of modified γ-Al2O3. Structure of active site and catalytic activity

Physico-chemical and catalytic properties of alumina exposed to P2O5, AlCl3, CH3AlCl2, PCl3, PCl5 and H2PO3F vapours have been studied. Catalysts obtained by treatment with P2O5, AlCl3 and CH3AlCl2 vapours are marked by very high acidity and catalytic activity which classify them among the solid superacids. From an i.r.investigation of ammonia adsorption coupled with e.s.r. measurements of perylene adsorption it has been demonstrated that solid superacids exhibit Lewis-type acid behaviour.The structure of the superacid site and the mechanism of hydrocarbon activation are proposed.