New silver- and vanadium-containing multimetal oxides for oxidation of aromatic hydrocarbons

Abstract

Carboxylic acids and carboxylic anhydrides such as benzoic acid, maleic anhydride, phthalic anhydride or pyromellitic anhydride are produced industrially by catalytic gas-phase oxidation of aromatic hydrocarbons such as benzene, o-xylene, naphthalene, toluene or durene in fixed-bed multitube reactors. Although the processes for the oxidation of o-xylene and/or naphthalene to phthalic anhydride have been studied very intensively for decades, there still is a need for improved catalysts with a selectivity to phthalic anhydride which is higher than 82 mol%. We have found a novel multimetal oxide catalyst of the formula Ag a− b M b V 2O x which allow significantly higher phthalic anhydride yield, since the new silver vanadium oxide catalysts can oxidize o-xylene significantly more selectively to form phthalic anhydride or intermediates than by using catalysts of the vanadium oxide/anatase type. By combining the new silver vanadates with conventional V 2O 5/TiO 2 catalysts, a PA yield of more than 84 mol% could be reached.