Process for purification of crude acetonitrile

Crude acetonitrile containing impurities such as hydrogen cyanide, allyl alcohol, oxazole and water is purified by at least one of the following processes (i) through (iv). (i) Process of removing hydrogen cyanide wherein crude acetonitrile is treated with an alkali in an amount sufficient to convert a substantial part of the free hydrogen cyanide present in the crude acetonitrile to an alkali metal cyanide but insufficient to convert a substantial part of the combined hydrogen cyanide present in the crude acetonitrile to an alkali metal cyanide; and then, the so obtained reaction mixture is subjected to distillation under reduced pressure. (ii) Process of removing allyl alcohol wherein the crude acetonitrile is subjected to extractive distillation in the presence of water in a rectifying column, while acetonitrile together with a small amount of water is recovered from the upper part of the column, and a concentrate of allyl alcohol in the form of a mixture with water and a small amount of acetonitrile is separated from the lower part of the column. (iii) Process of removing oxazole wherein the crude acetonitrile is subjected to extractive distillation in the presence of 0.5 to 5% by weight of water in a rectifying column, while a concentrate of oxazole in the form of a mixture with water and a small amount of acetonitrile is separated from the upper part of the column, and acetonitrile is recovered from the lower part of the column. (iv) Process of removing water lower part acetonitrile is treated with an alkali in an amount sufficient to extract water present in the crude acetonitrile, to be thereby divided into an organic liquid phase and an aqueous liquid phase, and the aqueous liquid phase is removed.