LACTAM PURIFICATION METHOD Russian patent published in 2004 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: invention relates to a method for purifying lactams, in particular ε-caprolactam, prepared by cyclization hydrolysis of aminonitrile. Method comprises removal of ammonia, and optionally solvent, from reaction medium followed by recovering purified lactam. Recovery is accomplished by means of at least one distillation of the lactam in presence of base, wherein are obtained: top fraction containing compounds more volatile than lactam, fraction containing high-purity lactam, and distillation residue containing lactam and higher-boiling compounds. Distillation residue is treated either by crystallization or by washing with water, or by treatment on ion-exchange resin, or by thin-layer evaporation, all treatment procedures allowing recovery of major part of lactam, which is recycled into distillation stage. EFFECT: increased purification efficiency. 15 cl, 2 dwg, 4 ex