SULPHUR RECYCLE IN FRACTIONATION OF A VINYLBENZENE

摘要

1391107 Distilling hydrocarbons UNIVERSAL OIL PRODUCTS CO 25 July 1972 [26 July 1971] 34692/72 Heading C5E In the separation of vinylbenzenes (e.g. styrene) from alkylbenzenes by distillation with the addition of elemental sulphur to inhibit polymerization, a high-boiling distillation residue containing sulphur is recycled to provide part of the inhibitor. As shown, a stream of fresh ethylbenzene from line 1 and recycled ethylbenzene from line 2 is dehydrogenated at 3. The product is cooled and separated at 5; an aqueous phase is discarded at 6 and a gas phase at 7. The hydrocarbon phase in line 8 with recycled material from line 10 and fresh sulphur from line 9 is distilled in three columns 11, 14 and 16. The distillate from column 11 is mainly benzene and toluene; that from column 14 is mainly ethylbenzene, and is recycled by line 2; that from column 16 is the desired product, styrene. The bottoms from each of the first two columns provides the feed to the next column, that from the third is fed to a wiped-film evaporator 19. Vapours from this evaporator pass back to column 16 by line 20; the residue is in part recycled by line 10 and in part removed by line 21 to avoid the build-up of heavy materials. Alternatively, the wiped-film evaporator can be by-passed by line 22. Distillation is preferably at reduced pressure.