METHOD FOR THE PREPARATION OF PYROMELLITIC ACID OR ITS ANHYDRIDE

摘要

67566-929 Pyromellitic acid or its anhydride is prepared by catalytic vapour phase oxidation of a tetra-C1-C4-alkylbenzene in the presence of a catalyst supported on an inert carrier, said catalyst comprising catalytically active material composed of 1 to 20 parts by weight of V2O5, 99 to 80 parts by weight of TiO2 and/or SnO2 and/or ZrO2, and per one hundred parts by weight of V2O5, TiO2 and/or SnO2 and/or ZrO2, 0.02 to 10 parts by weight, calculated as P2O5, of a phosphorus compound, 0.01 to 5 parts by weight, calculated as Nb2O5, of a niobium compound, 0 to 1.2 parts by weight, calculated as oxide, of at least one metal selected from the group consisting of potassium, cesium, rubidium and thallium, and 0 to 10 parts by welght, calculated as Sb2O3, of an antimony compound, and an inert carrier supporting said catalytically active material thereon.