Abstract: An improved catalyst suitable for use in the production of an unsaturated carboxylic acid by the catalytic vapor phase oxidation of an unsaturated aldehyde is provided. In this catalyst, a heat-resistant inorganic substance, such as alumina, silica-alumina and silicon carbide, having a particle diameter of 3 through 10 mm, an apparent porosity of 35 through 60%, a water absorption of 20 through 50%, an average pore diameter of not less than 40 microns, a specific surface area of not more than 2 m.sup.2 /g and a bulk specific gravity of 1.5 through 2.0 is used for supporting a composition containing molybdenum, phosphorus, vanadium and the alkali metals. The use of the above-mentioned carrier results in the advantages that the unsaturated carboxylic acid, such as methacrylic acid, can be selectively produced from the unsaturated aldehyde at a high yield and that the mechanical strength of the catalyst is remarkably improved.

Abstract: Methacrolein is produced in a high yield by catalytically oxidizing isobutylene at a temperature of from 250.degree. to 500.degree. C. by using a catalyst represented by the formula:Mo.sub.a Co.sub.b Fe.sub.c Bi.sub.d Cs.sub.e X.sub.f Y.sub.g O.sub.hwherein X is either both vanadium and palladium, Y is at least one member selected from titanium, nickel, tin and zirconium, a=12, b=2-12, c=0.5-7, d=0.1-5, e=0.0005-0.5, f=0.01-2, g=0-5 and h is a positive number proportional to the number of oxygen atoms satisfying the average valency of the metal atoms stated in the formula, which catalyst has a high resistance to compression and abrasion and exhibits a high catalytic efficiency, mechanical strength and durability.

Abstract: Unsaturated hydrocarbons having 4 to 6 carbon atoms are catalytically oxidized into maleic anhydride by using a catalyst, which consists essentially of oxides of (A) vanadium, (B) phosphorus, (C) titanium and (D) optionally at least one element selected from sodium, calcium, magnesium, iron, zirconium, boron, manganese, silver and molybdenum in the atomic ratios defined by the following formulaVP.sub.a Ti.sub.b X.sub.c O.sub.dwherein X is the element (D) set forth above and a=1.0 to 5.0, b=2.0 to 12.0 and c=0 to 1.0, and which catalyst is prepared by calcining a mixture of a vanadium-containing compound and titanium dioxide at a temperature of 650.degree. C. to 1,500.degree. C., incorporating into the mixture a phosphorus-containing compound and optionally the element "X"-containing compound and, then, heating the resulting mixture.

Abstract: Maleic anhydride is prepared by the catalytic oxidation of unsaturated hydrocarbons having 4 to 6 carbon atoms, at a temperature of from 350.degree. to 500.degree. C., in the presence of a catalyst which is produced by a method wherein a mixture of a titanium oxide and a vanadium compound in an atomic ratio of from 1 to 15 is calcined at a temperature of from 630.degree. to 1000.degree. C. to prepare a precursory catalyst, and wherein a gas mixture containing an organic phosphorus compound and a carrier gas is brought into contact with a mass of the percursory catalyst at a supply rate of the phosphorus compound being from 0.01 to 10 millimoles/hr per 1 ml of the mass of the percursory catalyst and at a temperature of from 350.degree. to 600.degree. C. during when a total amount of from 0.3 to 30 millimoles of the phosphorus compound per 1 ml of the mass of the precursory catalyst passes through the mass of the precursory catalyst.

Abstract: Unsaturated hydrocarbons having 4 to 6 carbon atoms are catalytically oxidized into maleic anhydride by using a catalyst, which consists essentially of oxides of (A) vanadium, (B) phosphorus, (C) titanium and (D) optionally at least one element selected from sodium, calcium, magnesium, iron, zirconium, boron, manganese, silver and molybdenum in the atomic ratios defined by the following formulaVP.sub.a Ti.sub.b X.sub.c O.sub.dwherein X is the element (D) set forth above and a=1.0 to 5.0, b=2.0 to 12.0 and c=0 to 1.0, and which catalyst is prepared by calcining a mixture of a vanadium-containing compound and titanium dioxide at a temperature of 650.degree. C. to 1,500.degree. C., incorporating into the mixture a phosphorus-containing compound and optionally the element "X"-containing compound and, then, heating the resulting mixture.

Abstract: Unsaturated hydrocarbons having 4 to 6 carbon atoms are catalytically oxidized into maleic anhydride at relatively low temperatures in the range of 300.degree. C to 450.degree. C. The catalyst used consists essentially of oxides of vanadium, phosphorus, zirconium, and at least one element selected from manganese, boron, cadmium, silver, bismuth and zinc.