A process for the manufacture of a phosphorus-vanadium and phosphorus-vanadium-co-metal catalysts suitable for use in the manufacture of maleic anhydride from butane which process comprises reacting at a temperature of about 0.degree. C. to about 200.degree. C. a vanadium compound in an organic ether solvent having about 2 to about 10 carbon atoms with a phosphoryl halide in the presence of water or an aliphatic alcohol having from about 1 to about 8 carbon atoms, eliminating the solvent and activating the catalyst by the addition of butane or other hydrocarbon feedstock and a phosphorus compound at a temperature of about 300.degree. C. to about 500.degree. C. The catalysts are useful for the manufacture of maleic anhydride from butane feedstock.