Vanadium phosphate: a new look at the active components of catalysts for the oxidation of butane to maleic anhydride

Vanadium phosphate catalysts have been extensively studied since the 1960s, when it was discovered that they are effective catalysts for the oxidation of butane to maleic anhydride. They represent the sole example of a commercialised material for the catalytic oxidation of an alkane. To date several hundred papers have been devoted to their study. Yet, virtually all studies have concentrated on two specific phases, namely the vanadyl hemihydrate precursor, VOHPO4.0.5H(2)O, which is converted into vanadyl pyrophosphate, (VO)(2)P2O7, which most researchers consider to be the active component of vanadium phosphate catalysts. In this feature article the nature of the active catalyst components is revisited and new approaches being pioneered in the synthesis of vanadium phosphates are described. In particular, detailed comments are made concerning the method of preparation and the role of crystalline and amorphous vanadium phosphate catalysts.