Preparation of superacids by metal oxides for reactions of butanes and pentanes

Recent works on preparation of solid superacid catalysts which are active for reactions of butanes and pentanes are reviewed. Sulfated metal oxides are obtained by adsorbing sulfate ion onto amorphous oxides of Fe, Ti, Zr, Hf, Sn, and Si followed by calcination in air; a superacid of Al2O3 is prepared from the crystallized oxide. Superacids by metal oxides are synthesized in the same manner as those of the sulfate superacids by supporting ZrO2, SnO2, TiO2, and Fe2O3 with WO3 and ZrO2 with MoO3 and B2O3. Metal promoted superacids which are highly active for the reaction of butane to isobutane are prepared by addition of salts of Pt, Ir, Rh, Ru, Os, Pd, Fe, and Mn (equivalent to Pt of 7.5 wt%) to sulfated zirconia gel followed by calcination, Similarly active catalysts are obtained by treatment of zirconia-supported Fe2O3 with sulfuric acid and calcination for long period.