Production of maleic anhydride from four-carbon hydrocarbons using catalysts prepared by water reflux techniques

Claim 1

In a process for the production of maleic anhydride by the oxidation of n-butane, n-butenes, 1,3-butadiene or a mixture thereof with molecular oxygen in the vapor phase at a reaction temperature of 250° C. to 600° C. in the presence of a catalyst comprising the mixed oxides of vanadium and phosphorus, the improvement wherein the catalyst is prepared by (a) forming an aqueous oxide slurry of a vanadium compound containing pentavalent vanadium; (b) adding to said aqueous oxide slurry a mineral acid-free, inorganic reducing agent capable of reducing said pentavalent vanadium to a valence state below +5 to obtain an aqueous slurry containing reduced vanadium, wherein said reducing agent is selected from the group consisting of ammonia, hydrazine, hydrazine hydrate, a finely divided metal or colloidal metal; (c) adding a phosphorus compound containing pentavalent phosphorus before the addition of the reducing agent or after the addition of the reducing agent; (d) heating said aqueous oxide slurry under reflux conditions; (e) removing the water from the resulting slurry to form a dried catalyst; and (f) calcining the dried catalyst at a temperature of 250° C. to 600° C.