Abstract: In conventional procedures for the preparation of phosphorus-vanadium-oxygen catalysts, with or without promoting elements or carriers, the phosphorus compounds and vanadium compounds are mixed under conditions to form precursors. These precursors are then heated to temperatures up to 600.degree. C. to form phosphorus-vanadium-oxygen catalysts suitable for the conversion of saturated hydrocarbons, such as butane, to maleic anhydride. The present invention employs a new phosphorus-vanadium-oxygen hydrogen intermediate composition which can be converted to the precursor. Catalysts formed from the intermediate are used, according to this invention, for the conversion of saturated hydrocarbons to maleic anhydride.

Abstract: An improvement in a method of preparing catalysts for the manufacture of maleic anhydride by oxidizing a saturated hydrocarbon. The catalyst is prepared by a process in which a catalyst precursor, containing tetravalent vanadium, is formed into agglomerates and calcined, the improvement being calcining the catalyst precursor at 325.degree.-375.degree. C. in the presence of oxygen and a saturated aliphatic hydrocarbon.

Abstract: In the method for the preparation of maleic anhydride by oxidizing an aliphatic hydrocarbon in the presence of a phosphorus-vanadium-oxygen complex catalyst, the improvement which comprises employing a catalyst with enhanced crush strength.

Abstract: In the preparation of phosphorus-vanadium-oxygen catalyst, where vanadium and phosphorus are contacted under conditions to provide a catalyst precursor with vanadium in the tetravalent state, and the precursor is formed into agglomerations and subsequently calcined at high temperatures, the improvement which comprises contacting the catalyst precursor with a non-aqueous solvent in an amount sufficient to enhance crush strength.

Abstract: In conventional procedures for the preparation of phosphorus-vanadium-oxygen catalysts, with or without promoting elements or carriers, the phosphorus compounds and vanadium compounds are mixed under conditions to form precursors. These precursors are then heated to temperatures up to 600.degree. C. to form phosphorus-vanadium-oxygen catalysts suitable for the conversion of saturated hydrocarbons, such as butane, to maleic anhydride. By the process of the present invention, a new phosphorus-vanadium-oxygen composition is formed which is converted to the precursor. Catalysts formed by the process of the present invention, when used for the conversion of saturated hydrocarbons to maleic anhydride, provide higher yields of maleic anhydride.

Abstract: In the method for the preparation of maleic anhydride by oxidizing an aliphatic hydrocarbon in the presence of a phosphorus-vanadium-oxygen complex catalyst, the improvement which comprises employing a catalyst with enhanced surface adhesion thereby reducing attrition during preparation of the maleic anhydride.

Abstract: In the preparation of phosphorus-vanadium-oxygen catalyst, where vanadium and phosphorus are contacted under conditions to provide a catalyst precursor with vanadium in the tetravalent state, and the precursor is formed into agglomerations and subsequently calcined at high temperatures, the improvement which comprises wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhesion prior to calcining.

Abstract: In a method for preparing a phosphorus-vanadium-oxygen catalyst wherein a pentavalent vanadium compound and a trivalent phosphorus compound are brought together in a liquid reaction zone under conditions to provide a substantial amount of tetravalent vanadium and to form a phosphorus-vanadium-oxygen catalyst precursor having a phosphorus to vanadium atom ratio between about 0.9:1 and about 2:1, the improvement of this invention comprises adding a sufficient amount of a surfactant to the liquid reaction zone to form a dispersion which comprises a liquid, the surfactant and a dispersoid of the phosphorus-vanadium-oxygen catalyst precursor.

Abstract: In a method for preparing a phosphorus-vanadium-oxygen catalyst wherein a pentavalent vanadium compound and a trivalent phosphorus compound are brought together in a liquid reaction zone under conditions to provide a substantial amount of tetravalent vanadium and to form a phosphorus-vanadium-oxygen catalyst precursor having a phosphorus to vanadium atom ratio between about 0.9:1 and about 2:1, the improvement of this invention comprises adding a sufficient amount of a surfactant to the liquid reaction zone to form a dispersion which comprises a liquid, the surfactant and a dispersoid of the phosphorus-vanadium-oxygen catalyst precursor.

Abstract: The productivity of phosphorus-vanadium-oxygen catalysts useful for converting saturated hydrocarbons containing from 4 to 10 carbon atoms to maleic anhydride can be increased by the order of preparatory steps used to prepare such catalysts. Phosphorus-vanadium-oxygen catalysts are prepared by mixing phosphorus and vanadium compounds to form precursors, shaping precursors and then calcining the precursors to form the catalysts. The catalysts are particularly beneficial for the conversion of butane to maleic anhydride.

Abstract: The prior art discloses that phosphorus-vanadium-oxygen catalysts wherein the phosphorus to vanadium atom ratio is between about 1:2 and about 2:1, and wherein at least about 20 atom percent of the vanadium is in the tetravalent state, are useful for the conversion of aliphatic hydrocarbons to maleic anhydride. It has now been found that when the pore volume of the catalysts from pores having diameters between about 0.8 micron and about 10 microns is greater than 0.02 cc/g, the catalyst is particularly useful for the conversion of saturated hydrocarbons, such as butane, to maleic anhydride.

Abstract: The performance of phosphorus-vanadium-oxygen catalysts useful for the conversion of saturated aliphatic hydrocarbons to maleic anhydride is dependent on the controlled calcination of the catalyst precursor. Phosphorus-vanadium-oxygen catalysts are prepared by mixing phosphorus and vanadium compounds to form precursors containing tetravalent vanadium, and calcining the precursors in an oxidizing atmosphere until a controlled level of pentavalent vanadium has been achieved, and then calcining the precursors in an inert atmosphere to higher temperatures to provide catalysts with the desired oxidation levels that are promptly active, so that valuable manufacturing facilities are not required to "activate the catalyst.