Production of polymethylbenzenes

Claim 1

A PROCESS FOR CONVERTING PSEUDOCUMENE INTO DURENE WHICH COMPRISES THE COMBINATION OF STEPS OF: (1) METHYLATING PSEUDOCUMENE WITH METHANOL IN VAPOR PHASE IN CONTACT WITH AN ACIDIC METHYLATING CATALYST UNDER CONDITIONS TO YIELD A PRODUCT CONTAINING SUBSTANTIAL PROPORTIONS OF BOTH TETRAMETHYLBENZENES AND PENTAMETHYLBENZENE; (2) SEPARATING THE PRODUCT, IN ADMIXTURE WITH A TRANSMETHYLATE FROM SUBSEQUENTLY DESCRIBED STEP (3), BY DISTILLATION TO RECOVER (A) AN INTERMEDIATE DISTILLATE CONSISTING ESSENTIALLY OF THE TETRAMETHYLBENZENE, (B) A LOWER BOILING DISTILLATE CONTAINING UNREACTED PSEUDOCUMENE AND (C)A HIGHER BOILING FRACTION CONTAINING THE PENTAMETHYLBENZENE; (3) SUBJECTING THE HIGHER BOILING FRACTION (C) IN ADMIXTURE WITH PSEUDOCUMENE TO VAPOR PHASE TRANSMETHYLATION CONDITIONS IN CONTACT WITH AN ACIDIC CATALYST TO PRODUCE A TRANSMETHYLATE CONTAINING A SUBSTANTIAL PROPORTION OF TETRAMETHYLBENZENES; (4) CYCLING THE TRANSMETHYLATE FROM STEP (3) TO THE DISTILLATION STEP (2); (5) SEPARATING DURENE FROM ISODURENE AND PREHNITENE IN THE TETRAMETHYLBENZENES DISTILLATE (A) BY CRYSTALLIZATION; AND (6) SUBSTANTIALLY RECYCLING THE LOWER BOILING DISTILLATE (B) TO AT LEAST ONE OF SAID PSEUDOCUMENE CONVERTING STEPS (1) AND (3).