| 摘要 |
Improved oxidation catalysts containing mixed oxides of vanadium and phosphorus which catalysts are particularly effective in the oxidation of n-butane, n-butenes, 1,3-butadiene or a mixture thereof with molecular oxygen or an oxygen-containing gas in the vapour phase to produce excellent yields of maleic anhydride with very good selectivity, are prepared by a process in which at least one vanadium compound, a substantial portion of which is in the pentavalent state, and at least one phosphorus-containing compound is added to an organic liquid medium capable of reducing at least a portion of the vanadium to a +4 valence state, to form a reaction mixture. Partial reduction of the vanadium is effected in the presence of the phosphorus-containing compound and a highly ordered and uniform mixed vanadium phosphorus oxide-containing catalyst precursor is formed. An oxidation catalyst comprising the mixed oxides of vanadium and phosphorus characterized by an average valence state of vanadium from +3.9 to +4.6, and a phosphorus to vanadium ratio of 1 : 1 to 1.2 : 1, wherein the macrostructure of the catalyst predominantly comprises generally spheroid particles consisting of stacks of integrally associated sheets of catalytic material is also disclosed. |
