Preparation of caprolactam

摘要

Caprolactam is prepared in a process comprising the following steps: (a) reacting the 5-formylvaleric ester with liquid ammonia as reaction medium and hydrogen in the presence of a ruthenium catalyst in liquid phase at from 80 DEG to 140 DEG C. under a hydrogen partial pressure of from 40 to 100 bar, (b) replacing the reaction medium ammonia by an aromatic hydrocarbon having a boiling point of from 80 DEG to 240 DEG C. which is liquid under the reaction conditions, (c) heating the resulting mixture in liquid phase under superatmospheric pressure at 230 DEG -350 DEG C. to form caprolactam, and (d) isolating caprolactam from the resulting reaction mixture.