GB1432690A - Process for separating high purity aromatic hydrocarbons from mixtures containing them - Google Patents

Abstract

1432690 Extractive distillation SNAMPROGETTI SpA 23 Nov 1973 [29 Nov 1972] 54612/73 Heading C5E Aromatic hydrocarbon 14 is recovered from a feed 1 which comprises at least 80% by weight of aromatic hydrocarbons by subjecting the feed to extractive distillation in a column 2 at 50-200‹ C. with a solvent mixture 19 comprising water and an organic solvent to produce an overhead 3, which is condensed and separated into a water stream 8 which is recycled, together with a portion of the non-aromatics, to the column 2 at one or more points above the point at which the feed 1 and the solvent mixture 19 is fed, and a bottom 9 comprising the purified aromatic hydrocarbons, organic solvent and water; the bottoms 9 is rectified in a column 11 to separate an overhead 20 and a bottoms 17, comprising organic solvent and water, which is recycled to the column 2 as the stream 19. The overhead 20 can be condensed and separated into a water stream, which is in part recycled as the stream 15 and in part vaporized at 18 and recycled as the stream 16, and the aromatic product 14. The solvent can comprise N-formyl morpholine, 2-formyl morpholine, 3-formyl morpholine and morpholine-acetone and suitably contains 0À5-25 wt. per cent water. As illustrated in Fig. 2 (not shown) the extractive distillation and rectification can be carried out in upper and lower portions respectively of a single column. The examples relate to the separation of an artificial feed comprising (a) 95 wt. per cent benzene and 5% n-heptane and (b) 70% benzene, 20% toluene, 5% xylene and 5% non-aromatic hydrocarbons.