Preparation of superacid of iron-supported zirconia for reaction of butane to isobutane

A highly active superacid of 2 wt% Fe-supported ZrO₂ for the skeletal isomerization of butane to isobutane was obtained by sfexposing Fe₂O₃/ZrO₂ to 1 N H₂SO₄ followed by calcining in air at 700°C for more than 24 h; the Fe₂O₃/ZrO₂ was prepared by impregnating zirconia gel with a solution of Fe(NO₃)₃ followed by drying at 300°C (2 wt% Fe). A much lower activity was observed with the opposite procedure, where the first impregnation was sulfation of the gel, followed by a second impregnation with the iron compound. It was proved from analysis of the sulfur content in the catalysts that residual sulfur species were not related with generation of the superacidic sites. XPS showed the catalyst to be Fe₂O₃ supported on ZrO₂.Superacids by metal oxides, VIII. For previous publications VI and VII in this series see refs. 10,11].