Patent GB-834145-A (GB)
Title: Process for the recovery of ªÏ-aminocapronitrile from mixtures of ªÏ-aminocapronitrile, ªÏ-caprolactam and water
IPC: C07C255/24
Filed: 1957-12-20
Abstract: o -Aminocapronitrile is recovered from mixtures thereof with o -caprolactam and water, such as are obtained by the reaction of caprolactam with ammonia, by first removing all or most of the water, at least a last part by evaporation with an inert organic solvent which forms an azeotrope with water, and recovering aminocaprolactam from the residue by distillation.  Up to 75% by weight of the water in the crude mixture may be removed by rapid evaporation prior to the addition of the organic solvent, e.g. at 70-80 DEG  C. and 100-200 mm. Hg.  Up to 2% by weight of water in the residue after the azeotropic distillation does not cause the formation of material amounts of high-boiling products in the subsequent distillation of amino-capronitrile.  In a preferred form of the invention, the initial crude mixture is subjected in the vaporous form to a fractional condensation treatment in two or more stages so that more water is condensed in the final stage than in the preceding stage(s), not more than 75% by weight of the water in the final condensate is evaporated off, the resulting concentrate is mixed with the condensate resulting from the preceding condensation stage(s), an inert organic solvent capable of forming an azeotrope with water is added to the combined condensates in an amount sufficient for the removal of 25-75% by weight of the water present in the condensate, the solvent is evaporated simultaneously with said water (by simple evaporation or azeotropic distillation), and the residual liquid is subjected to continuous distillation to recover aminocapronitrile, leaving caprolactam as residue.  The condensate from the above azeotropic distillation may be separated into aqueous and organic phases, the former being mixed with the condensate of the final condensation stage, and the organic phase being treated for the recovery of solvent.  Suitable solvents are benzene, the xylenes, toluene, cyclopentane and cyclohexane.ALSO:o -Aminocapronitrile is recovered from mixtures thereof with o -caprolactam and water, such as are obtained by the reaction of caprolactam with ammonia, by first removing all or most of the water, at least a last part by evaporation with an inert organic solvent which forms an azeotrope with water, and recovering aminocaprolactam from the residue by distillation.  Up to 75% by weight of the water in the crude mixture may be removed by rapid evaporation prior to the addition of the organic solvent, e.g. at 70-80 DEG  C. and 100-200 mm. Hg.  Up to 2% by weight of water in the residue after the azeotropic distillation does not cause the formation of material amounts of high boiling products in the subsequent distillation of amino-capronitrile.  In a preferred form of the invention, the initial crude mixture is subjected in the vaporous form to a fractional condensation treatment in two or more stages so that more water is condensed in the final stage than in the preceding stage(s), not more than 75% by weight of the water in the final condensate is evaporated off, the resulting concentrate is mixed with the condensate resulting from the preceding condensation stage(s), an inert organic solvent capable of forming an azeotrope with water is added to the combined condensates in an amount sufficient for the removal of 25-75% by weight of the water present in the condensate, the solvent is evaporated simultaneously with said water (by simple evaporation or azeotropic distillation), and the residual liquid is subjected to continuous distillation to recover aminocapronitrile, leaving caprolactam as residue.  The condensate from the above azeotropic distillation may be separated into aqueous and organic phases, the former being mixed with the condensate of the final condensation stage, and the organic phase being treated for the recovery of solvent.  Suitable solvents are benzene, the xylenes, toluene, cyclopentane and cyclohexane.