A production process, especially a continuous production process, for a biphenyltetracarboxylic
acid tetraester characterized by carrying out, in parallel, a step of preliminarily
mixing a phthalic acid diester and a palladium compound-containing catalyst to
prepare a starting mixture, a step of continuously or intermittently supplying
the starting mixture to a reactor, a step of conducting oxidative dimerization
reaction of the phthalic acid diester in a temperature range of from 140
C. and lower than 250 C. while supplying molecular oxygen to the reactor
to form a reaction mixture in the reactor, and a step of continuously or intermittently
removing a portion of the reaction mixture from the reactor. Preferably, the palladium
compound-containing catalyst in the starting mixture is dissolved in the phthalic
acid diester, the palladium compound-containing catalyst comprises a palladium
compound, a bidentate ligand and a copper compound, the reactor consists of a plurality
of serially connected reactors and a carboxylic acid is also continuously or intermittently
supplied to the reactor.
