Patent ID: 9562008
Date: 2017-02-07
CPC Classifications: C07D

Claim:
1. A process for the recovery of ε-caprolactam from extract water of polycaprolactam obtained by hydrolytic polymerization, comprising the following process steps: a. by single- or multistage distillation the extract water is concentrated by separation of water, wherein a first intermediate product stream is obtained, whose concentration of ε-caprolactam is increased with respect to the extract water; b. the first intermediate product stream is separated by distillation into a first vaporous ε-caprolactam-water phase and a liquid oligomer-ε-caprolactam phase; c. into the liquid oligomer-ε-caprolactam phase steam is introduced in the presence of a catalyst, wherein the ε-caprolactam oligomers are hydrolytically depolymerized to monomeric ε-caprolactam, and ε-caprolactam is stripped out of the phase by the steam, wherein a second vaporous ε-caprolactam-water phase is obtained and wherein non-depolymerizable impurities are discharged from the process as bottom product; d. the first vaporous ε-caprolactam-water phase formed in step b) and the second ε-caprolactam-steam phase formed in step c) are combined to a unified ε-caprolactam-water phase, from which water is separated by distillation and thus an oligomer- and water-free ε-caprolactam phase is obtained as second intermediate product stream;