Patent ID: 7390897

Claim:
A method for making ε-caprolactam (CL) from 6-aminocapronitrile (ACN), comprising: (a) contacting a vaporized mixture of ACN and water in a reactor, the reactor comprising a dehydration catalyst, to produce a vapor phase reaction product comprising CL, ammonia, water and ACN; (b) separating the ammonia and a major portion of the water from the vapor phase reaction product to produce a crude liquid caprolactam comprising CL, ACN and a minor portion of the water; (c) contacting the crude liquid caprolactam with hydrogen in the presence of a hydrogenation catalyst in a hydrogenation reactor to produce a hydrogenated crude caprolactam comprising CL, hexamethyleneimine (HMI), hexamethylenediamine (HMD) and water; (d) removing water and HMI from the hydrogenated crude caprolactam in a dehydration column to produce an anhydrous crude caprolactam comprising CL and HMD; (e) introducing the anhydrous crude caprolactam into a low boiler distillation column, wherein the low boiler column distillate comprises HMD, and the low boiler column tails comprises CL and high boilers; and (f) introducing the low boiler column tails into a high boiler distillation column, wherein the high boiler column distillate comprises CL and the high boiler column tails comprises high boilers.