GB1353448A - Process for preparing lactams - Google Patents

Abstract

1353448 Lactam preparation STAMICARBON NV 9 May 1972 [10 May 1971] 21549/72 Heading C2C [Also in Division C5] Lactams are obtained by the Beckmann rearrangement of a cyclic ketoxime in the presence of H 2 SO 4 or oleum, neutralization of the resulting mixture with NH 3 or an ammonium base, separation of the resulting product into a lactam layer and an aqueous layer, extraction of the lactam from the former with a solvent and recovery of the lactam from the resulting solution, crystallization of (NH 4 ) 2 SO 4 from the aqueous layer, evaporation of the residue from the lactam extraction until it is substantially saturated with (NH 4 ) 2 SO 4 , addition of the thussaturated solution to the mother liquor from the ammonium sulphate crystallization, adjustment of the lactam concentration of the resulting mixture to >0À8% by weight (e.g. 1-2% by weight) and separation of the thus-adjusted mixture into an oily layer and a residual aqueous layer. The former oily layer may be used as a fuel oil and the latter aqueous layer, comprising an ammonium sulphate solution only slightly contaminated with organic substances, may be recycled to the (NH 4 ) 2 SO 4 crystallization stage or to the neutralization stage. Lactam may also be recovered from the oily layer by extraction. Starting cyclic ketoximes having 5 to 12 C atoms in the ring are specified and the example describes the production of caprolactam from cyclohexanone oxime.