Transalkylation process.

摘要

Alkylation-transalkylation process involving alkylation of an aromatic substrate with a C2-C4 alkylating agent coupled with separation to recover a monoalkylated aromatic product and liquid phase transalkylation of a polyalkylated product. Both the alkylation and transalkylation reactions carried out in the liquid phase over molecular sieve aromatic alkylation and transalkylation catalysts. The output from the alkylation reaction zone is separated to provide a lower boiling fraction comprising the aromatic substrate and a higher boiling fraction comprising a mixture of monoalkylated and polyalkylated aromatics which is separated to the to produce the monoalkylated fraction and a higher boiling polyalkylated fraction. At least a portion of the polyalkylated fraction including substantially all dialkylated and trialkylated aromatics is supplied, along with the aromatic substrate, to a transalkylation reaction zone operated under liquid phase conditions to cause disproportionation of the polyalkylated fraction to arrive at a disproportionation product having a reduced polyalkylated aromatic content and an enhanced monoalkylated aromatic content which is supplied to the first separation zone. A benzene feed stock and a C2-C4 alkylating agent are supplied to an alkylation reaction zone containing a molecular sieve alkylation catalyst and which is operated to produce an alkylated product comprising a mixture of monoalkyl and polyalkyl benzenes. The alkylation zone may be operated under liquid phase or vapor phase conditions with the output from the alkylation zone being subjected to separation steps. The transalkylation reaction zone is operated at an average temperature below the average temperature of the alkylation reaction zone and under conditions to maintain the benzene in the liquid phase. In the production of ethylbenzene, in which the alkylation reaction takes place over an aromatic alkylation catalyst selected from the group consisting of zeolite beta and zeolite omega, the output from the alkylation reaction zone is supplied to a benzene separation zone. A higher boiling fraction comprising an ethylbenzene polyethylbenzene mixtures is supplied from the benzene separation zone to an ethylbenzene separation zone. This zone is operated to produce a lower boiling product fraction comprising ethylbenzene and a higher boiling fraction comprising polyethylbenzene containing no more than 5 wt. % ethylbenzene. The polyethylbenzene fraction is supplied along with benzene to a transalkylation reaction zone which preferably contains a transalkylation catalyst selected from the group consisting of zeolite y and zeolite omega.