Method for manufacture of phthalic anhydride

摘要

A method for the manufacture of phthalic anhydride by the catalytic oxidation of naphthelene or ortho-xylene which comprises contacting a mixed gas consisting of naphthalene or ortho-xylene and a molecular oxygen-containing gas with a catalyst bed comprising a first catalyst packed on the upstream side of the flow of mixed gas and a second catalyst packed on the down-stream side of the flow, wherein the first catalyst has carried on a nonporous inactive carrier a catalytically active component composed of 67 to 90% by weight of titanium dioxide, 9 to 30% by weight of vanadium pentoxide and 0.7 to 3% by weight of a rubidium compound (calculated as Rb2SO4), and the second catalyst has carried on the nonporous inactive carrier a catalytically active component composed of 67 to 94% by weight of titanium dioxide, 5 to 30% by weight of vanadium pentoxide and at least one member selected from the group consisting of 0.1 to 1% by weight of a tin compound (calculated as SnO2) and 0.5 to 3% by weight of a phosphorus compound (calculated as SnO2).