Simultaneous nylon monomers from DuPont/BASF
15 Jan 2000
New plants which produce two comonomers of nylon simultaneously could be at the centre of a new joint venture between BASFand DuPont. The plants will make hexamethylene diamine (HMD) which is used in nylon 6,6 and caprolactam used in nylon 6 in a pair of reactors.
The starting point for the process is a feedstock containing hydrogen, ammonia and adiponitrile. This passes through a tubular reactor, packed with a cobalt catalyst, which converts the adiponitrile into a mixture of hexamethylene diamine and aminocapronitrile. The reaction mixture undergoes a series of distillations, with ammonia and some of the adiponitrile recycled back into the reactor. The hexamethylene diamine is recovered.
Unreacted adiponitrile from the first reactor is pumped into the second reactor, where it meets a titanium dioxide catalyst. This converts the adiponitrile into caprolactam.
The process is based on butadiene, via a DuPont process which converts this hydrocarbon into adiponitrile by nickel-catalysed addition of hydrogen cyanide. Unlike current caprolactam processes, which generally use oximes, this process does not make an ammonium sulphate by-product.
BASF and DuPont plan to use this process in a new plant, probably to be located in China, which will make roughly equal quantities of the two compounds.
