US 8,231,765 B2 · Process for the purification of lactams

Abstract

A method and a plant are disclosed for purifying lactams, particularly lactams obtained by cyclizing hydrolysis of aminonitrile. The purification of ε-caprolactam obtained by cyclizing hydrolysis of aminocapronitrile is described which includes eliminating the ammonia from the reaction medium of the hydrolysis, then recovering the lactam from the medium in purified form. The recovery is carried out by performing at least a distillation of the lactam in the presence of a base producing optionally a fronts fraction having compounds more volatile than the lactam, a fraction having the lactam to be recovered to the degree of desired purity and a distillation tails having the lactam and compounds less volatile than the lactam. The distillation tails are treated by various processes such as evaporation in thin layers to recover the major part of the caprolactam and recycling the latter in the purification process.

Claims20

Dependent claims

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.

5 more elements

Dependencies are inferred from the claim text.

Process for the purification of lactams

Life of this patent

Process for the purification of lactams

Life of this patent

Abstract

Claims20