GB1051190A - - Google Patents

Abstract

1,051,190. Separating acetonitrile and acrylonitrile. FARBENFABRIKEN BAYER A.G. Dec. 19, 1963 [Dec. 19, 1962; July 4, 1963], No. 50225/63. Heading B1L. [Also in Division C2] Acrylonitrile is separated from acetonitrile in gaseous mixtures containing them, by washing out the acetonitrile at a first stage with water and thereafter removing the acrylonitrile at a second stage with water wherein a portion of the water for the first stage is derived from the second stage. The gaseous mixture may be derived from catalytic oxidation of propylene or acrolein in the presence of ammonia, and may also contain HCN. The separation may be effected at the same pressure and temperature for both stages, or different pressures and/or temperatures may be used for the two stages. The gaseous mixture is added at 1 or 1a and passed to absorber A which is supplied with water containing acrylonitrile by 4. The gas mixture free of acetonitrile leaves at 2 and is washed in absorber B by water from 6 while the residual gases leave at 7. The water from absorber B leaves at 4 and part is withdrawn at 5 for recovery of acrylonitrile while the residium passes from absorber A by 3 to be worked up. The pressure of operation may be chosen so that the wash water from absorber B leaves pipe 4 as two phases, the aqueous phase being passed to absorber A whilst the other phase is distilled directly. In an alternative embodiment (Fig. 2 not shown) the two stages are combined into one continuous column with a pipe mid-way along its length to extract some of the water containing acrylonitrile. In another embodiment (Fig. 3, not shown), the gaseous effluent from the first absorber is compressed and cooled to liquify the acrylonitrile. The two phase mixture containing acrylonitrile and water is treated to remove the organic phase and return the aqueous phase to the first absorber.