DE1807654

1,239,460. Acrylonitrile, separation from acetonitrile. NITTO CHEMICAL INDUSTRY CO. LTD. 6 Nov., 1968 [8 Nov., 1967; 30 April, 1968], No. 52639/68. Heading B1B. [Also in Division C2] Acrylonitrile is separated from an aqueous solution containing acrylonitrile and acetonitrile by submitting the solution A to extractive distillation in column 1' using water as extracting agent and withdrawing acrylonitrile (together with some water) as vapour B from the top of the column; the aqueous liquor withdrawn from the base of column 1' is introduced into stripping column 2', which is operated under elevated pressure e.g. 0.5 to 5 kg/cm2 gauge, and the overhead vapours (a mixture of acetonitrile and water) are condensed in condenser 3' by heat-exchange with a cooling liquid which is thereby caused to boil and, at least partly, vaporize. In a preferred embodiment, as shown, the cooling liquid for condenser 3' is liquor withdrawn through pipe 10' from a middle section of column 2'. The vapours formed therefrom are introduced through pipe 11' into the lower section of column 1', and the non-vaporized liquid is returned to column 2' through pipe 12'. The aqueous liquor withdrawn from the base of column 2' is submitted to pressurereduction in vessel 4'; the vapours so formed are introduced through pipe 8' into the lower section of column 1', and the residual liquor is introduced through pipe 9' into the upper section of column 1'. In a modified system, the liquor from the base of column 2' is used as cooling liquid for condenser 3'. In another modification, some of the liquor withdrawn from the base of the extractive distillation column is used as cooling liquid for the condenser attached to the stripping column. The initial feed mixture may be derived from the catalytic ammoxidation of propylene or acrolein; and the residual cooling liquid from the condenser may be used to absorb the gases from the reaction zone.