GB828710A - Improvements in and relating to the production of acrylonitrile - Google Patents

Abstract

Acrylonitrile is produced by passing through a reaction zone containing a heated aqueous cuprous chloride solution, acetylene, and hydrogen cyanide in an amount exceeding the amount required for the conversion of said acetylene to acrylonitrile, reacting said acetylene and hydrogen cyanide in said reaction zone to form acrylonitrile, passing the gases containing said acrylonitrile and acetaldehyde formed as a by-product in said reaction zone into an absorption zone, reacting said acetaldehyde and said excess of hydrogen cyanide in said absorption zone to form lactonitrile, removing said acrylonitrile and lactonitrile together from said absorption zone, recycling the residual gases into said reaction zone, and separating said acrylonitrile and lactonitrile. The formation of lactonitrile may be effected by means of an alkaline catalyst, e.g. sodium cyanide or sodium hydroxide. The absorption zone is maintained at a temperature of - 10 DEG to + 20 DEG C., advantageously about 0 DEG C. The acrylonitrile and lactonitrile are removed from the absorption in the form of an aqueous alkaline emulsion. Part of the emulsion may be recycled and passed through the absorption zone countercurrently to the gases to absorb the acrylonitrile contained therein. The emulsion can be stabilized by acidification and separated by distillation into acrylonitrile and lactonitrile. The latter may be acidulated with acetic acid and subjected to fractional distillation to split it into acetaldehyde and hydrogen cyanide. The hydrogen cyanide is recycled, with the gases leaving the absorption zone, to the reactor. The optimum concentration of HCN in the gases leaving the reactor is 10 to 15 g. per cu. m.