GB1479103A - Separation of hydrocarbons - Google Patents

Abstract

1479103 Separating C 4 hydrocarbons by extractive distillation SNAM PROGETTI SpA 17 Jan 1975 [1 Feb 1974] 2230/75 Heading C5E C 4 diolefinic hydrocarbon is separated from a hydrocarbon mixture which contains at least 0À1% by weight of acetylenic hydrocarbon by subjecting the mixture to extractive distillation in the presence of a polar solvent to obtain the majority of the C 4 diolefinic hydrocarbon as overhead and stripping the bottoms product to produce an overhead containing the acetylenic hydrocarbon and a bottoms containing the polar solvent and a diluent comprising at least one saturated, olefinic or cyclic C 5 or C 6 hydrocarbon is introduced and recycled to maintain the concentration of acetylenic hydrocarbon below a dangerous value. In the example, a feed 1 consisting of 48À8% but-1-ene, 50% buta- 1,3-diene and 1À2% vinyl acetylene is extractively distilled at 2 to produce an overhead 4 comprising water, but-1-ene and some buta-1,3- diene and a bottoms 7 which is extractively distilled at 9. The polar solvent fed to columns 2 and 9 consists of N-formyl morpholine containing 5% water. The overhead from the column 9 comprises the buta-1,3-diene, a little water and some tens of p.p.m. of cyclohexane and of vinyl acetylene. The bottoms 14 is stripped at 15 to produce an overhead containing some buta-1,3-diene, all the vinyl acetylene and some cyclohexane, a bottoms 22 which is recycled as the extractive solvent. A side stream 19 comprising cyclohexane and water is condensed to separate a water stream 21 and a stream 20 of cyclohexane which is recycled as the diluent. The acetylene present can be either vinyl acetylene or diacetylene.