GB1081984A - Process for the separation of adiponitrile - Google Patents

Abstract

The concentration of adiponitrile in a stream (e.g. the low boiler removal column make obtained in the distillation of the products derived from the electrohydrodimerisation of acrylonitrile) comprising a mixture of mainly adiponitrile and 3-hydroxypropionitrile together with acrylonitrile, succinonitrile and a -methyl-glutaronitrile is continuously increased by: (a) feeding the stream into a reaction zone wherein the stream is heated in the range 130 DEG -225 DEG C.; (b) concurrently with the stream, feeding into the reaction zone an aqueous solution of a compound having an alkaline reaction selected from the group consisting of alkali metal hydroxides (e.g. lithium, sodium or potassium hydroxide), alkaline earth metal hydroxides (e.g. calcium or barium hydroxides), and quaternary ammonium hydroxides which have as alkyl groups saturated aliphatic radicals containing from 1 to 8 carbon atoms; (c) withdrawing from the reaction zone a volatile make containing acrylonitrile; and (d) withdrawing residual adiponitrile enriched bottoms from the reaction zone. In the preferred process the low boiler removal column make, the aqueous solution preferably containing 1 to 45% weight per cent of the compound having an alkaline reaction and an optional sparge of water are fed to a reactor still so that the alkaline compound is present in an amount preferably not less than 0.01% based on the stream weight; the reactants, which preferably have a residence time of 0.1 to 2 hours in the reaction zone, are brough to the desired temperature by circulation through an electrically or steam-heated re-boiler; acrylonitrile vapour (formed by the dehydration of the 3-hydroxypropionitrile) leaving the reactor is condensed in a water-cooled condenser and is separated in a decanter; and the desired adiponitrile containing reaction bottoms are withdrawn from the foot of the reactor.