CO-PRODUCTION OF PARAXYLENE AND STYRENE FROM MIXTURE OF XYLENES AND ETHYLBENZENE, USEFUL AS RAW MATERIALS FOR SYNTHESIS OF POLYMERS SUCH AS POLYAMIDES AND POLYSTYRENE

摘要

PURPOSE: A process for the co-production of paraxylene and styrene of high purity by stages of separation, dehydrogenation and isomerization is provided. CONSTITUTION: The process for co-production of high purity paraxylene and styrene from a charge containing xylenes, ethylbenzene and 9 - 10C hydrocarbons comprises the following stages: (1) distillation of the charge to separate xylenes, from which a head flux comprising mainly metaxylene, paraxylene, ethylbenzene and part of the orthoxylene, and at the base 9 - 10C hydrocarbons and remaining orthoxylene; (2) an adsorption stage of the head flux in a primary adsorption column containing numerous adsorbent beds, interconnected in a closed loop, with varying selectivity for paraxylene, ethylbenzene, metaxylene and orthoxylene and comprising 4 zones of a desorption zone for paraxylene, a desorption zone for ethylbenzene, an adsorption zone for paraxylene and a zone between extraction of raffinate and injection of desorbent; (3) distillation of the extract to obtain pure(99.7%) paraxylene and desorbent which is recycled to the adsorption column; (4) distillation of the raffinate, containing metaxylene, orthoxylene and ethylbenzene; (5) dehydrogenation of the distilled raffinate, the effluent containing styrene, metaxylene, orthoxylene, unconverted ethylbenzene and by-products, at least 50% of the ethylbenzene being converted to styrene; (6) elimination of by-products to produce a mixture containing mainly styrene, ethylbenzene, metaxylene and orthoxylene; (7) separation of the mixture to produce a primary flux containing styrene (99.8%) and a secondary flux containing metaxylene and orthoxylene; and (8) isomerization of the second flux and recovery of paraxylene, orthoxylene and metaxylene which are recycled to the distillation column for the charge.