Patent ID: 6914154

Claim:
A method for producing a biphenyltetra-carboxylic acid tetraester, comprising: providing a reaction mixture comprising a phthalic acid diester and a palladium compound-containing catalyst in a reactor, continuously or intermittently supplying a starting mixture to a portion of the reaction mixture in the reactor, wherein the starting mixture has been preliminarily prepared by mixing a phthalic acid diester and a palladium compound-containing catalyst outside the reactor, the palladium compound-containing catalyst being dissolved in said phthalic acid diester in the starting mixture, conducting an oxidative dimerization reaction of the phthalic acid diester in the presence of the palladium compound-containing catalyst at a temperature in a range of from 140° C. to less than 250° C. in the reactor while supplying molecular oxygen to the reaction mixture in the reactor, and continuously or intermittently removing a portion of the reaction mixture from the reactors, wherein the method is carried out in a continuous manner and the supplying, the reaction and the removing are carried out in parallel.