METHOD OF PURIFYING ADIPONITRILE

1396115 Continuous purification of adiponitrile BADISCHE ANILIN- & SODAFABRIK AG 4 Oct 1972 [5 Oct 1971] 45730/72 Heading C2C The continuous purification of adiponitrile is effected by cooling the impure adiponitrile in a crystallization zone, indirectly by the evaporation of liquid ammonia (e.g. at -18‹ to -6‹C.), to form a suspension of finely divided solid adiponitrile (e.g. mean diameter 0À1 to 1 mm.) in liquid adiponitrile, separating the solid from the liquid, washing the solid dinitrile with liquid adiponitrile, separating the mother liquor, obtained after separation of the solid dinitrile, into two unequal portions by weight, returning the larger (e.g. 55 to 90% by weight of the total) without intervening treatment to the crystallization zone and purifying the smaller part by distillation before returning this also to the crystallization zone. The suspension produced preferably contains 30 to 50% by weight of solid dinitrile and is conveniently allowed to stand before being separated. The liquid adiponitrile used to wash the solid is preferably pure liquid adiponitrile obtained by melting some of the separated crystals and may be returned to the crystallization zone after use. 1 - Cyanocyclopentanimine - 2 is obtained as contaminant from that portion of mother liquor subjected to purification by distillation.