Clean caprolactam
6 Dec 2000
Sumitomo Chemical has developed a new process to manufacture caprolactam, the nylon intermediate, without producing ammonium sulphate, the main by-product of current processes. The company plans to use the process in conjunction with another system, developed by EniChem, which produces the essential raw material.
The Sumitomo process converts cyclohexanone oxime, methanol and hydrogen directly to caprolactam by passing the reactants over a solid catalyst, a metal-containing pentasil-type zeolite structure. The reaction is 95.7 per cent selective towards caprolactam, and gives conversion yields greater than 99 per cent. The catalyst is continually withdrawn to a regeneration vessel, where it is heated to decompose carbon-containing residues.
Conventionally, caprolactam is made by treating cyclohexanone oxime with sulphuric acid. This produces ammonium sulphate as a co-product. There is a market for this compound — it's used as a fertiliser — but prices are generally very low.
The process is currently at a demonstration plant stage, although the company is planning to commercialise it in the near future. This is likely to be in conjunction with an EniChem process which produces cylcohexanone oxime with near-100 per cent yields from cyclohexanone, ammonium and hydrogen peroxide.
