Caprolactam purification - by distillation accompanied by oxidation with chromates and/or dichromates

摘要

The chromates and/or bichromates e.g. Na or K chromate or bichromate, are added as solids or satd. solns. to the molten caprolactam, as obtained by the catalytic gas phase transformation from cyclohexanone oxime in amt. =2% with respect to the caprolactam. The oxidising purification is effected at k0-300 degrees C, pref. 80-200 degrees C under reduced press. e.g. 1-120 mm Hg press. distillation of the molten caprolactam occurring simultaneously. The prefd. pH during the process is 4.5-8.