GB736856A - Improvements in and relating to the separation of hydrocarbons - Google Patents

Abstract

A xylene-rich fraction is produced from a mixture of hydrocarbons comprising ethyl benzene, xylenes and aliphatic and/or naphthenic saturated hydrocarbons by a process comprising subjecting the mixture to extractive distillation with a monohydroxy phenol boiling within the range of from 215 DEG to 255 DEG C. at atmospheric pressure, taking off as overhead product a fraction containing substantially all the non-aromatic hydrocarbons, ethyl benzene and at most only 10 per cent of its weight of xylenes and as bottom product a solution of aromatic hydrocarbons substantially free from non-aromatics and having an increased xylene content and an increased weight ratio of xylenes: ethyl benzene. The hydrocarbon mixtures treated suitably contain at least 40 per cent of saturated non-aromatics, at least 5 per cent of xylenes and an amount of ethyl benzene from 5 to 30 per cent by weight of the total xylenes; the preferred mixtures boil between 125 DEG and 155 DEG C. Distillation may be effected in a bubble cap, sieve plate or packed column. The bottoms product of desired xylene-rich fraction in phenolic solvent is fed to a stripping column wherein the xylenes are removed as overhead-product and the solvent is withdrawn from the base and returned to the extraction column. The preferred phenolic solvent is a cut boiling from 215-255 DEG C. and containing a small proportion only of compounds in which both the 2- and 6- positions are alkyl-substituted. Examples are given. Specifications 563,930 and 571,913, [Group IV], are referred to. According to the Provisional Specification, the extractive solvent may be any polar solvent having a B.P. at least 50 DEG C. higher than that of o-xylene.