ABSTRACT

The addition of hydroxylamine sulphate to cyclohexane gives cyclohexanone oxide which, followed by a Beckmann rearrangement, yields caprolactam. The major problem with multi-stage processes has been the formation of substantial quantities of ammonium sulphate by-product, over four tonnes for each tonne of caprolactam produced. Around 60% of caprolactam is produced from cyclohexane, 30% from phenol, 5% from toluene and the remainder from nylon waste. After separation from the aqueous solution, anhydrous oxime is converted to caprolactam by heating to 100–120°C with 27% oleum. The caprolactam solution, diluted with water to give a 50% acid concentration, is extracted with a countercurrent of alkylphenol. Around 80% of caprolactam is used for the manufacture of nylon 6 fibres, and the remainder for nylon 6 resins and other copolymers. Steel is recommended for storage. Caprolactam must be stored in a well ventilated, cool area away from strong oxidizing agents.