PROCESS FOR THE SEPARATION OF ACRYLONITRILE AND ACETONITRILE

1,239,957. Separating acrylonitrile and acetonitrile. FARBENFABRIKEN BAYER A.G. and ERDOLCHEMIE G.m.b.H. 24 June, 1968 [24 June, 1967], No. 29944/68. Heading B1L. [Also in Division C2] Gaseous mixtures of acrylonitrile and acetonitrile, also containing hydrocyanic acid, which mixtures are obtained by the catalytic oxidation of propylene in the presence of ammonia, are passed by line 1 to column A where the bulk of the mixture is absorbed in water containing a little acetonitrile fed in by line 7; gaseous residues including some acetonitrile pass out by line 11. Liquid effluent passes to an intermediate point of column B by line 2 to which steam is supplied by link 4 at the base and water by line 3 at the head. The overhead withdrawn by line 5 consists principally of acrylonitrile and hydrocyanic acid, while the bottoms consists of aqueous acetonitrile, some of which is fed back to column A by line 7 while the remainder passes by line 8 to a point 1 near the head of column C, to which steam is supplied by line 9. The overhead from column C removed by line 10 comprises a concentrated aqueous solution of acetonitrile, while the bottoms, consisting of water is passed back to the head of column B. If the feed gas only contains a little acetonitrile e.g. less than 320 kg. per 54,800 m3. gas, column C may be omitted and the entire bottoms from column B returned to column A, the overhead 11 containing acetonitrile being burned, part of the aqueous liquid thus freed from acetonitrile then being used as extracted liquid in column B.