Process for continuous purification of crude caprolactam prepared from 6-aminocapronitrile

Abstract

Crude capronitrile is purified by hydrogenation, subsequent treatment in an acidic medium and subsequent distillation in an alkaline medium, by a process in which (a) 6-aminocapronitrile is converted into crude caprolactam by reaction with water, (b) high boilers and low boilers are separated off from the crude caprolactam from step (a), (c) the crude caprolactam from step (b) is treated with hydrogen at from 50.degree. to 150.degree. C. and from 1.5 to 250 bar in the presence of a hydrogenation catalyst and, if desired, of a solvent to give a mixture A, (d1) mixture A in a solvent is passed, at from 30.degree. to 80.degree. C. and from 1 to 5 bar, over an ion exchanger containing terminal acid groups to give a mixture B1, or (d2) mixture A is distilled in the presence of sulfuric acid, any solvent present being removed before the addition of the sulfuric acid, to give a mixture B2, and (e) mixture B1 or mixture B2 is distilled in the presence of a base to give pure caprolactam.

Dependencies are inferred from the claim text.