Patent GB-779402-A (GB)
Title: Improvements in or relating to the recovery of butadiene-1:3 from hydrocarbon mixtures thereof
IPC: C07C7/10
Filed: 1952-11-26
Abstract: Butadiene-1:3 is extracted by an aqueous cuprous ammonium acetate solvent from a predominantly C4 hydrocarbon stream including hydrocarbons more soluble in the solvent by a process comprising intimately contacting the hydrocarbon stream with a stream of the solvent in the ratio of about 1:1 to 10:1 by weight of hydrocarbon to solvent thereby dissolving a minor proportion of the butadiene-1:3 present and substantially all of the hydrocarbons more soluble than the butadiene-1:3, separating the treated hydrocarbon stream containing the bulk of the butadiene-1:3 from the solvent, recovering from the solvent dissolved butadiene and the more soluble hydrocarbons as a butadiene-1:3 stream substantially free from the more soluble hydrocarbons and a separate hydrocarbon stream comprising the more soluble hydrocarbons in a series of stripping steps and passing the treated hydrocarbon, stream containing the bulk of the butadiene-1:3 to an extraction unit for recovery of the diene with aqueous cuprous ammonium acetate, preferably using a weight ratio of hydrocarbon stream to solvent of 1 to 10.  A suitable C4 hydrocarbon stream comprises isobutylene, n-butylene, 1:3-and 1:2-butadienes, butane and minor amounts of acetylene and C3 and C5 hydrocarbons including propadiene and may be obtained by dehydrogenating a butylene hydrocarbon mixture.  In a preferred process illustrated by drawings (not shown) such a C4 stream is mixed with C.A.A. solvent in a weight ratio of 5:1.  The treated hydrocarbon stream containing the bulk of the butadiene-1:3 is separated from the solvent, and passed to the main butadiene extraction unit.  The solvent is fed to a flash-drum whereby most of the dissolved butadiene-1:3 is flashed off together with butylenes. The solvent is then passed into a stripper (see Group III) from which is taken an overhead stream of residual butadiene-1:3 and a side stream comprising acetylene, propadiene, butadiene-1:2 and any other of the more soluble hydrocarbons present.  The butadiene-1:3 streams from the flash-drum and stripper are returned after removal of impurities to the extraction system with fresh feed.  The stripped solvent is recycled.  Specification 582,713, [Group IV], is referred to.ALSO:<PICT:0779402/III/1> In a process for the recovery of aqueous cuprous ammonium acetate solvent used in the partial extraction of butadiene-1:3 from a predominantly C4 hydrocarbon stream (see Group IV(b)), the solvent containing butadiene-1:3, butylenes and hydrocarbons more soluble than the butadiene is submitted to distillation to remove separately gaseous streams of butadiene-1:3 and a mixture of the more soluble hydrocarbons.  As shown, the solvent is fed via line 7 to a stripping tower 8A operated at 9 p.s.i.g. whereby an overhead stream of mainly butadiene-1:3 is removed and the paritally stripped solvent is then fed to tower 8B operated at 6 ps.i.g. whereby residual butadiene-1.3 and acetylene and other hydrocarbons present are stripped off.  Another embodiment of the process employs a single stripping tower from which the hydrocarbons are removed as two overhead streams.  Specification 582,713 [Group IV] is referred to.