Verfahren zur Trennung von Acrylnitril und Acetonitril

摘要

1,269,195. Separating acrylonitrile. ERDOLCHEMIE G.m.b.H. and FARBENFABRIKEN BAYER A.G. 13 April, 1970 [24 April, 1969], No. 17350/70. Heading B1L. [Also in Division C2] A process for recovering acrylonitrile from a gaseous mixture obtained by the catalytic oxidation of propylene in the presence of ammonia and comprising acrylonitrile, hydrocyanic acid, acetonitrile, propionic acid nitrile, water and at least one inert gas comprises passing the aqueous solution obtained by washing out the gaseous mixture in a scrubber to a multi-plate stripping column; wherein water at a temperature of from 15‹C, to 75‹C is supplied to the top of the stripper column so that substantially acetonitrile only is washed out of the gaseous mixture ascending the column whilst acrylonitrile, hydrocyanic acid and propionitrile are withdrawn at the top of the column; wherein a portion of the water together with all the acetonitrile is removed as .a subsidiary stream from the lower part of the stripper column in the region of the 12th to 25th plate; and wherein this subsidiary stream is supplied as the wash water to the top of the scrubber, the acetonitrile contained in this water is driven off at the top of the scrubber by the gas which is substantially free from acrylonitrile, and the remaining water is removed at the sump of the column and, after it has been cooled to from 15‹C to 75‹C the remaining water is completely or partly returned to the top of the stripper column. At least part of the mixture of water and acetonitrile may be removed as a subsidiary stream to a distillation column, wherein the acetonitrile is freed from the mixture and withdrawn from the top of the distillation column and the sump discharge from the distillation column is carried to the top of the wash column, wherein any remaining mixture of acetonitrile and water is also conveyed to the top of the wash column and the acetonitrile is substantially driven off from the wash water by the reaction gases flowing through the column, and wherein the reaction gas entering at the bottom of the wash column is washed by the wash water which has been freed from most of the acetonitrile and which enters the wash column at the top.