Method for producing catalysts for gas phase oxidation of saturated and/or unsaturated C.sub.4 -hydrocarbons to maleic anhydride

Abstract

A method for producing catalysts for gas phase oxidation of saturated or unsaturated hydrocarbons to maleic anhydride is disclosed comprising: (a) mixing a vanadium compound containing pentavalent vanadium with orthophosphoric acid in an alcohol from the series of monohydric lower aliphatic alcohols having 2-8 C-atoms in the optional presence of promoters, and a reducing agent combination of H.sub.3 PO.sub.3 +alcohol wherein the sum of H.sub.3 PO.sub.3 and H.sub.3 PO.sub.4 is so controlled that an atomic ratio of P to V of 1.0 to 1.2 is attained and wherein said H.sub.3 PO.sub.3 is used in such sub-stoichiometric amounts that it is sufficient to reduce the vanadium to an oxidation state only of 4.2 to 4.4, and then said reducing agent combination is used to further reduce the vanadium to an oxidation state between 3.9 to 4.0, any water if present being distilled off as an azeotrope with the alcohol by heating; (b) adding titanium dioxide obtained through high temperature pyrolysis of titanium tetrahalide and optional additional promoters Ni, Fe, Li, Mg; (c) forming precipitated catalyst in a known manner; and (d) activating the catalyst in an oxidation reactor at temperatures of about 450.degree. to 510.degree. C. for about 12 to 72 hours in the presence of an air-hydrocarbon stream.

Dependencies are inferred from the claim text.