PRODUCTION OF PHTHALIC ANHYDRIDE BY GAS PHASE OXIDATION OF O-XYLOL IN A PRIMARY AND A SECONDARY REACTOR

PRODUCTION OF PHTHALIC ANHYDRIDE BY GAS PHASE OXIDATION OF O-XYLOL IN A PRIMARY AND A SECONDARY REACTOR 5 THE INVENTION RELATES TO A METHOD FOR PRODUCING PHTHALIC ANHYDRIDE BY CATALYTIC GAS PHASE OXIDATION OF O-XYLOL. ACCORDING TO SAID METHOD, A GASEOUS MIXTURE OF O-XYLOL AND AN OXYGEN-CONTAINING GAS IS REACTED IN A PRIMARY REACTOR TO GIVE A GASEOUS INTERMEDIATE REACTION PRODUCT WHICH CONTAINS UNREACTED O-XYLOL, PHTHALIC ANHYDRIDE REACTION PRODUCTS WITH A LOWER OXIDATION 10 STATE AND PHTHALIC ANHYDRIDE, THE REACTION HEAT PRODUCED IN THE PRIMARY REACTOR BEING AT LEAST PARTIALLY CARRIED OFF BY INDIRECT COOLING WITH A HEAT EXCHANGE MEDIUM, AND INTRODUCING THE INTERMEDIATE REACTION PRODUCT TO A SECONDARY REACTOR. THE CONCENTRATION OF THE UNREACTED O-XYLOL IN THE INTERMEDIATE REACTION PRODUCT IS AT LEAST 1BY WEIGHT, AND THE SUM OF THE 15 CONCENTRATIONS OF PHTHALIC ANHYDRIDE OF THE LOWER OXIDATION STATE IN THE INTERMEDIATE REACTION PRODUCT IS AT LEAST 0.5BY WEIGHT. THE METHOD ACCORDING TO THE INVENTION ALLOWS AN INCREASE IN TOTAL YIELD OF PHTHALIC ANHYDRIDE WITHOUT ANY OR WITHOUT SUBSTANTIAL DECREASE IN PRODUCT QUALITY.