Caprolactam purification by crystallisation from benzene toluene - and xylenes

摘要

Crude lactam, prepared for example by cyclohexanone oxime re-arragnement in the presence of solid catalysts, such as B2O3, is dissolved in benzene or in a 7 - 8C alkylbenzene; precipitated by stirring and cooling to 0 - 50 degrees C; crystal suspension is filtered optionally after repeated re-crystallisation from benzene or 7 - 8C alkylbenzenes; and treated epsilon-caprolactam is distilled in vacuo. Pure epsilon-caprolactam is obtained, suitable for production of fibre-forming polyamides. Process can be adapted for purifying other lactams, or for purifying lactams obtained from polyamide waste. By-products as well as non-converted oxime are removed.