GB1493489A - Process for the recovery of high purity paraxylene - Google Patents

Abstract

1493489 Purification of para-xylene by crystallisation STANDARD OIL CO 11 March 1975 [11 March 1974] 10118/75 Heading B1G A process for separating para-xylene having a purity in excess of 99% from a liquid mixture of xylenes and C 8 aromatics comprises cooling the mixture to a temperature just above the p-xylene eutetic to form a slurry and separating a substantial portion of mother liquor from the slurry to form a porous p-xylene cake having entrained mother liquor therein, washing the cake with from 0.4- 1.2 parts by wt, of wash liquid per part of cake, the wash liquid comprising a major portion of a C 5 -C 8 hydrocarbon and a minor portion of dissolved p-xylene, and separating a substantial portion of the wash liquid from the washed cake to recover the product of p-xylene. It is preferred to carry out the process using a continuous feed multiple zone centrifugal separator unit as shown in Fig. 2 in a first zone of which solid-liquid separation is effected whereby a substantial portion of the mother liquor is extracted and discarded. The p-xylene filter cake passes to a second zone where it is washed, preferably with hexane containing 5-30 parts of p-xylene at a temperature of about 70‹F. The wash liquor effluent is distilled to recover a mixture of xylene iximers for recycle and hexane for revise. The washed cake is dried in a third zone of the separator and passed to a melt tank and a fractionation tower to remove hexane and so yields high purity pxylene product.