Improvements in or relating to the purification of acrylonitrile and acetonitrile

摘要

Acrylonitrile and acetonitrile are separated from a mixture containing the two compounds together with impurities, such as propionitrile and other higher nitriles, by submitting the mixture to fractionation in the presence of a countercurrent stream of water in a multiplate distillation column, from which an aqueous mixture containing the impurities (together with some acrylo- and aceto-nitrile) is removed from the 5th to the 15th plate below the point of introduction of the feed mixture into the column. A vapour mixture of acrylonitrile and water is obtained at the head of the column; and an aqueous solution of acetonitrile is withdrawn from the base of the column. The vapour mixture from the head of the column is condensed. The condensate separates into an aqueous phase and an acrylonitrile (saturated with water) phase. The latter may be dried to obtain pure acrylonitrile as final product. The aqueous phase may be supplied to the top plate of the column. The aqueous solution withdrawn from the base of the column may be concentrated by distillation to obtain the acetonitrile/water azeotrope.