GB818722A - Improvements in the manufacture of acrylonitrile - Google Patents

Abstract

A crude aqueous acrylonitrile solution containing acetaldehyde, obtained by reacting HCN and acetylene to form an acetylene-bearing gas and scrubbing said gas with water, is refined by distillation, characterized in that a free -HCN content in excess of that stoichiometrically equivalent to the acetaldehyde content is provided in the solution. The acrylonitrile solution obtained from the scrubber may be subjected to steam stripping to concentrate it, a free-HCN content in excess of the acetaldehyde being provided in the concentrated acrylonitrile which is then distilled to produce a purified acrylonitrile product. The amount of excess HCN is not critical and may be provided for in any suitable manner. Preferably the HCN feed to the HCN-acetylene reactor is such as to ensure the required excess. The excess HCN may also be provided by adding sufficient HCN directly prior to, following, or during the steam stripping operation. In examples: (2) illustrates the distillation of a crude wet acrylonitrile containing sufficient free HCN to react with all of the free acetaldehyde; (1) is a comparative example; (3)-(12) illustrate experiments conducted on acrylonitrile solutions containing differing amounts of HCN and acetaldehyde to determine the stability against polymerization, the method utilized being the oxygen bomb induction period method described in Specification 600,708.