Production of dicarboxylic acids or anhydrides thereof

Claim 1

IN A PROCESS FOR THE PRODUCTION OF BENZENE DICARBOXYLIC ACID ANHYDRIC COMPRISING OXIDIZING A MIXTURE OF ALIPHATIC-SUBSTITUTED BENZENES CONTAINING A MAJOR PROPORTION OF ALIPHATIC BENZENES HAVING TWO ALIPHATIC GROUPS POSITIONED ORTHO TO EACH OTHER ON THE BENZENE RING AND A MINOR BUT SUBSTANTIAL PROPORTION HAVING META AND PARA ALIPHATIC SUBSTITUENTS BY CONTACTING SAID ALIPHATIC BENZENES AND A STOICHIMETRICALLY EXCESSIVE AMOUNT OF AN OXYGEN-CONTAINING GAS WITH A VANADIUM OXIDE CATALYST AT A TEMPERATURE ABOVE ABOUT 800* F., THE IMPROVED METHOD WHICH COMPRISES MIXTURE A SUBSTANTIAL AMOUNT OF A LOW BOILING SULFUR COMPOUND SELECTED FROM THE GROUP CONSISTING OF SULFUR DIOXIDE, SULFUR TRIOXIDE, CARBON DISULFIDE, HYDROGEN SULFIDE, LOWER MERCAPTANS, LOW BOILING ALKYL SULFIDES AND DISULFIDES, AND THIOPHENES WITH THE VAPORIZED ALIPHATIC-SUBSTITUTED BENZENES AND OXYGEN-CONTAINING GAS PRIOR TO THEIR CONTACT WITH THE CATALYST, THE AMOUNT OF THE SULFUR COMPOUND CALCULATED AS EQUIVALENT SULFUR DIOXIDE BEING FROM ABOUT 0.01% TO ABOUT 15% BY WEIGHT BASED ON THE ALIPHATIC-SUBSTITUTED BENZENE FEED.