Abstract: Provided is a catalyst for producing an unsaturated carboxylic acid, in which a ratio of a diffraction line intensity of 2?=19.1±0.3° with respect to a diffraction line intensity of 2?=10.7±0.3° in X-ray diffraction measurement is 0.20 or more and less than 0.

Abstract: Disclosed is a method for producing a catalyst for producing methacrylic acid by subjecting methacrolein or the like to vapor phase catalytic oxidation, which contains, as essential active components, Mo, V, P, Cs, NH4 and Cu, the method including (a) a step of preparing a heteropoly acid aqueous solution or the like (A liquid) containing, as constituent elements, Mo, P and V; (b) a step of mixing a part of the resulting A liquid with a cesium compound aqueous solution or the like (B liquid); and (c) a step of mixing the remainder of the A liquid with the B liquid to prepare a slurry liquid (C liquid).

Abstract: There is provided a hetero polyacid-based catalyst for methacrylic acid production, which is more excellent in performance, life and moisture absorption during storage, the catalyst being a catalyst for methacrylic acid production, wherein a proton is replaced so as to satisfy conditions of ?=A+(B×C) and 0.5???1.4 when the atomic ratio of the alkali metal atom relative to 10 atoms of Mo is taken as A and the atomic ratio of the copper atom relative to 10 atoms of Mo is taken as B in MoaPbVcCudYeZfOg where Y represents cesium or the like; Z represents iron or the like; and a to g represent each an atomic ratio of each element relative to 10 atoms of Mo.

Abstract: An object of the present invention is to provide a process for producing a catalyst for gas-phase contact oxidation of methacrolein, isobutyraldehyde or isobutyric acid to produce methacrylic acid in a high yield and a high selectivity, and a catalyst wherein an alkali metal element, particularly cesium among alkali metal elements, is added by a specific method in a partially neutralized salt of a hetero polyacid which contains Mo, V, P, an alkali metal element and NH4 as essential active ingredients, the catalyst being characterized by having extremely high catalytic performance.

Abstract: There is provided a hetero polyacid-based catalyst for methacrylic acid production, which is more excellent in performance, life and moisture absorption during storage, the catalyst being a catalyst for methacrylic acid production, wherein a proton is replaced so as to satisfy conditions of ?=A+(B×C) and 0.5???1.4 when the atomic ratio of the alkali metal atom relative to 10 atoms of Mo is taken as A and the atomic ratio of the copper atom relative to 10 atoms of Mo is taken as B in MoaPbVcCudYeZfOg where Y represents cesium or the like; Z represents iron or the like; and a to g represent each an atomic ratio of each element relative to 10 atoms of Mo.