| abstract |
e -Caprolactam is prepared by heating at least one of the compounds e - caprolactone, e -hydroxycaproamide and amide forming derivatives of e -hydroxycaproic acid, in aqueous ammonia, in an atmosphere comprising free hydrogen to a temperature within the range 200-420 DEG C., under a pressure at least sufficient to maintain a liquid phase in the reaction zone. Suitable derivatives of e -hydroxycaproic acid are its alkyl, cycloalkyl, aralkyl and aryl esters, or its ammonium and alkali metal salts. The reaction may be carried out in an atmosphere of hydrogen alone, or hydrogen mixed with other inert gases, e.g. nitrogen and helium. In this case the partial pressure of hydrogen is advantageously 0.01-100 atms. The preferred concentration of ammonia is 0.1-35% by weight, and the preferred mol. ratio of caproic acid derivative starting material to aqueous ammonia (in terms of pure ammonia) ranges from 1:1 to 1:25. The lactam is isolated from the aqueous ammonia solution of lactam produced and after the extraction the residue may be recycled. |