Production of pyromellitic anhydride involves oxidation of tetra alkyl benzene on a mixed oxide catalyst containing vanadium, tungsten and co-catalyst metals, supported on rutile and tungsten and/or silicon carbide

摘要

Pyromellitic dianhydride is made by oxidation of 1,2,4,5-tetra-alkylbenzene using a catalyst comprising mixed oxides of: (a) vanadium and tungsten; (b) Group IA and/or IIA metals; (c) manganese, antimony, bismuth, phosphorus, copper, aluminum and/or titanium; and (d) a Group VIIIB metal, on a rutile/(tungsten and/or silicon carbide) support. The production of pyromellitic acid dianhydride comprises: (1) preparation of a starting material containing 1,2,4,5-tetra-alkylbenzene of formula (I): and (2) selective oxidation of (I) at 300-450 deg C in presence of a catalyst system comprising: (A) a support consisting of rutile and tungsten carbide and/or silicon carbide; (B) a catalyst based on a mixture of vanadium and tungsten oxides; and (C) a cocatalyst based on a combination of (c1) a Group IA and/or IIA metal oxide, (c2) oxide(s) of Mn, Sb, Bi, P, Cu, Al and/or Ti and (c3) a Group VIIIB metal oxide, giving a catalyst/cocatalyst combination of formula (II): R1 = CH3; R2, R3, R4 = 1-3C alkyl V = vanadium; MI = tungsten; MII = Mn, Sb, Bi, P, Cu, Al and/or Ti; MIII = a Group VIIIB element; MIV = an alkali and/or alkaline earth metal; a = 0.1-10; b = 0.01-1; c = 0-0.5; d = 0.01-0.6; X = 7-40.