Patent ID: 6624326
Filing Date: 2003-09-23
Classification: B01J,C07C

Abstract:
A process for producing methacrylic acid through vapor phase oxidation or vapor phase oxidehydrogenation of at least one of methacrolein, isobutyl aldehyde and isobutyric acid in the presence of a heteropolyacid catalyst containing a heteropolyacid composed of at least one of molybdophosphoric acid and molybdobvanadophosphoric acid or a salt of the heteropolyacid, characterized in that said heteropolyacid catalyst has been prepared by a method comprising preparing an aqueous solution or aqueous dispersion which(1) contains the nitrogen-containing heterocyclic compound, nitrate anions and ammonium ions, (2) the ammonium ion content not exceeding 1.7 moles per mol of the nitrate anion content, and (3) the ammonium ion content not exceeding 10 mols per 12 mols of the molybdenum atom content, by mixing raw materials containing the catalyst-constituting elements with the nitrogen-containing heterocyclic compound in the presence of water, drying and calcining the same.