Manufacture of maleic anhydride

Claim 1

CONTINUOUS PROCESS FOR THE MANUFACTURE OF MALEIC ANHYDRIDE, IN WHICH A HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BENZENE AND TOLUENE IS CATALYTICALLY OXIDIZED IN VAPOR PHASE WITH AIR IN A REACTION ZONE TO PRODUCE A MALEIC ANHDRIDE EFFLUENT, WHICH COMPRISES PASSING THE EFFLUENT THROUGH A COOLING ZONE, AND THERE CONDENSING AND SEPARATING AS A LIQUID PHASE A PORTION OF THE MALEIC ANHYDRIDE CONTENT OF THE EFFLUENT, PASSING THE UNCONDENSED PORTION OF THE EFFLUENT INTO A SCRUBBING ZONE AND THERE CONTACTING IT WITH WATER TO REMOVE THE RESIDUAL MALEIC ANHYDRIDE CONTENT OF THE EFFLUENT AND CONVERT IT TO MALEIC ACID IN WATER SOLUTION, WITHDRAWING MALEIC ACID-WATER SOLUTION FROM THE SCRUBBING ZONE AT A RATE SUCH AS TO MAINTAIN THE MALEIC ACID CONCENTRATION OF THE SOLUTION IN THE RANGE ABOUT 25 TO ABOUT 50 PERCENT BY WEIGHT, PASSING THE WITHDRAWN MALEIC ACID-WATER SOLUTION INTO THE INTERMEDIATE PORTION OF A DEHYDRATION COLUMN, PASSING THE CONDENSED LIQUID MALEIC ANHYDRIDE INTO THE LOWER PORTION OF SAID DEHYDRATION COLUMN, SAID DEHYDRATION COLUMN CONTAINING AN ORGANIC LIQUID CAPABLE OF FORMING AN AZETROPIC MISTURE WITH WATER, DISTILLING THE WATER AND SAID ORGANIC LIQUID, AS AN AZETROPIC MIXTURE, SEPARATING THE ORGANIC LIQUID FROM THE WATER, RETURNING A MAJOR PROPORTION OF THE ORGANIC LIQUID TO THE LOWER PORTION OF THE DISTILLATION COLUMN, AND A MINOR PROPORTION TO PROVIDE REFLUX TO THE UPPER PORTION OF THE COLUMN, WITHDRAWING MALEIC AMHYDRIDE FROM THE LOWER PORTION OF THE DEHYDRATION COLUMN, AND CONTINUOUSLY SUBJECTING IT TO DISTILLATION TO PURIFY IT.