Antimony, bismuth, tin or lead oxide catalysts - for producing phthalic anhydride by catalytic oxidation of o-xylene

摘要

Title catalysts comprise an inert support of irregular 3-6mm grains of silicon carbide, alumina and/or aluminium silicate coated with 35-75% oxides of antimony, bismuth, tin and/or lead with 25-65% other metal oxides, the oxides forming 8-16% of the total catalyst. Pref. other metal oxides are 20-55% titanium oxide and 5-10% vanadium oxide. A process for oxidising o-xylene to phthalic anhydride uses the above catalyst preferably at 300-450 degrees C with 12-19 mols oxygen/mol of o-xylene, particularly using air. Previous processes using anadium titanium oxide catalysts have been limited to an o-xylene concentration of 47 g/m3 whereas using the above a concentration over 50g/m3 is obtained and a phthalic anhydride production rate over 330g/hr/l catalyst.