Abstract: A phosphorus vanadium oxide catalyst for the oxidation of a C.sub.4 hydrocarbon. The catalyst comprises a shaped body having a volume, or a fixed bed comprising shaped bodies having an average volume, of at least about 0.02 cc, and contains a promoter selected from among Bi, Sb, Ge, Ti, Zr, La, Ce, Ni, Zn, U, Sn, Si or mixtures thereof. The promoter is present in a proportion that enables the catalyst to have a developed surface area of at least about 28 m.sup.2 /g, and to exhibit a weight/area productivity of at least about 3.5 mg maleic anhydride/m.sup.2 -hr and/or a weight/weight productivity of at least about 100 g maleic anhydride/kg.cat.-hr. when contacted with a gas containing 2.4% by volume n-butane in air, at a gas flow volume to catalyst weight ratio of 2180 cc/g-min., under a pressure of 1.055.times.10.sup.2 -kPa-G, and at a temperature sufficient to maintain a hydrocarbon conversion of 85 mole percent. Methods for the preparation of the catalyst include activation by ANST.