Production of phthalic anhydride by catalytic oxidation

Claim 1

A PROCESS FOR THE CATALYTIC VAPOR PHASE OXIDATION OF O-XYLENE TO PHTHALIC ANHYDRIDE WHICH COMPRISES LEADING A GAS CONTAINING MOLECULAR OXYGEN TOGETHER WITH 150 TO 600 G. OF THE O-XYLENE PER CUBIC METER (S.T.P.) OF OXYGEN OVER A FINELY DIVIDED CATALYST IN FLUIDIZED FORM AT A TEMPERATURE OF 250* TO 420*C., SAID CATALYST COMPRISING A MIXTURE, BEING IN A LIQUID MOLTEN CONDITION AT THE REACTION TEMPERATURE, OF VANADIUM PENTOXIDE, SODIUM PYROSULFATE AND POTASSIUM PYROSULFATE AS ACTIVE CONSTITUENTS WITH A RATIO BY WEIGHT OF SODIUM PYROSULFATE TO POTASSIUM PYROSULFATE OF ABOUT 1:9 TO 1:1 AND A HIGHLY POROUS INERT CARRIER MATERIAL WITH AN INNER SURFACE OF 200 TO 400 SQUARE METERS PER GRAM AND A GRAIN SIZE OF 10 TO 3,000 MICRONS AS A CARRIER FOR THE MOLTEN MIXTURE, SAID MOLTEN MIXTURE CONSTITUTING 10 TO 60% OF THE TOTAL CATALYST AND CONTAINING 5 TO 40% OF VANADIUM PENTOXIDE WITH REFERENCE TO THE AMOUNT OF SAID MOLTEN MIXTURE OF ACTIVE CONSTITUENTS.