JPS6147574B

PURPOSE:To obtain a catalyst compsn. based on a mixt. of P and V oxides having high activity in oxidation even at relatively low temps. by mixing a P cpd. and a V cpd. in an aq. medium under the condition making the valence of V 4.0-4.3 after which the resulting solid is calcined and washed with water. CONSTITUTION:A tetravalent V cpd. such as VOCl 2 and a P cpd. such as metaphosphoric acid are mixed in an aq. medium at 50-150, esp. 70-100 deg.C so that the atomic ratio of P/V becomes 1.0-1.2. In place of the V cpd. a V cpd. having a valence of 4.0-4.3 may be prepared by mixing a pentavalent V cpd. such as V2O5 with a reducing substance such as hydrochloric acid. The above liquid mixt. is then evaporated to dryness to remove the aq. medium. The resulting R-V cpd. solid contg. about 1-10 wt% water is calcined at above 350, esp. 500-550 deg.C and washed with water to remove water sol. parts. The yielded catalyst compsn. shows high activity esp. in formation of maleic anhydride by oxidation of butane.