Preparation of fluidizable vanadium phosphorus oxide catalysts and use thereof in production of maleic anhydride

摘要

A process is provided for preparing fluid bed catalysts containing the mixed oxides of vanadium and phosphorus prepared from a mixed phosphoric acid source. The process comprises(a) introducing at least one pentavalent vanadium compound into an organic liquid capable of reducing at least a portion of the vanadium to a valence state of +4;(b) effecting reduction of at least a portion of the vanadium to a valence state of +4;(c) contacting the vanadium with a mixed phosphorus component prior or subsequent to effecting said reduction, wherein said mixed phosphorus component comprises 75-90 weight percent orthophosphoric acid and 10-25 weight percent pyrophosphoric acid;(d) comminuting the catalyst precursor resulting from step (a)- (c);(e) introducing the catalyst precursor into water prior or subsequent to said comminuting to form an aqueous slurry; and(f) spray drying said slurry to form microspheroidal catalyst particles.;The catalysts are used in the oxidation of C₄-hydrocarbons, in particular n-butane to maleic anhydride.