PROCEDE POUR LA PREPARATION D'ACIDES CARBOXYLIQUES INSATURES PAR OXYDATION CATALYTIQUE ET CATALYSEUR CONVENANT A CETTE FIN

A process is disclosed for the preparation of acrylic acid or methacrylic acid by reacting in vapor phase acrolein or methacrolein with molecular oxygen or with an oxygen-containing gas, at a temperature between 200 DEG and 350 DEG C., in the presence of a solid catalyst and with a contact time between 0.5 and 5 seconds, characterized in that said catalyst consists of molybdenum, vanadium, tungsten, one or more of the elements selected from the class consisting of silver, titanium, chromium, cerium, lanthanum and tantalum, and oyxgen chemically combined with the above-indicated elements, and wherein the atomic ratios between the various elements present in the catalyst are represented by the empirical formula: Mo12VaWbXcOd wherein X represents one or more of the elements Ag, Ti, Cr, Ce, La, Ta; a varies between 0.5 and 10; b varies between 0.5 and 8; c varies between 0.1 and 3 for X=Ag and from 0.3 to 4 for each of the elements Ti, Cr, Ce, La, Ta; with the further proviso that if X consists of 2 or more elements, then their sum shall not exceed 8 atoms; and d is a number that satisfies the valency requirements of the other elements. The catalyst may be carried on a support, and the reaction may be carried out in the presence of an inert gaseous diluent or water vapor.