Abstract
3, 4, 3', 4'-Biphenyltetracarboxylic acid (s-BTC) derivatives are now widely recognized as a useful compound. The anhydride (s-BPDA) is a raw material for polyimide which is the most heatproof resin, and it is known that the carboxylate has unique functions as a plasticizer.
Although it is supposed to be difficult to form biphenyl structure on a factory scale, there are two industrial methods. The first method is oxidative dimerization of dimethyl phthalate by palladium catalyst and the second is reductive dimerization of 4-chlorophthalic acid by palladium catalyst.
In 1994, the latter process was established in our laboratory and then we started the industrial production on hundreds tons per year according to the process flow diagram (Fig. 2).
