Patent ID: 8231765

Claim:
A process for the purification of lactams obtained from a hydrolysis reaction medium comprising an aminonitrile, a lactam, ammonia and a solvent used in the cyclizing hydrolysis of an aminonitrile, the process consisting in: a. removing ammonia and optionally solvent from the hydrolysis reaction medium; and b) recovering the lactam from the reaction medium by distilling said lactam at least once in the presence of a base and recovering: (i) optionally a top fraction comprising compounds which are more volatile than the lactam, (ii) a fraction comprising the lactam having higher purity of the lactam than was present in the reaction mixture and (iii) a distillation bottom product comprising lactam and compounds with a higher boiling point than the lactam, c. treating said distillation bottom product and recovering said lactam from said distillation bottom product, and d. recycling said recovered lactam from said distillation bottom product, wherein treating said distillation bottom product consists of evaporating a thin-layer of the lactam, crystallizing the lactam, or separating the lactam from impurities by extracting the lactam with water.