Ube Industries, Inc.

Akira Ishikawa

Katsuo Imatani

Masaki Kashibe

Hiroto Mitsui

Norihisa Komoda

Kiyotaka Akao

A tetraester of 3,3&prime;,4,4&prime;-biphenyltetracarboxylic acid is advantageously prepared by a process composed of a step of dimerizing an o-phthalic diester in the presence of a catalyst comprising a powdery palladium salt having a specific surface area of at least 0.5 m,/g and a basic bidentate ligand compound and one or more steps of continuing the dimerization after supplemental addition of at least one of the powdery palladium salt and the basic bidentate ligand compound.

Preparation of tetraester of 3, 3&prime;, 4, 4&prime;, - biphenyltetracarboxylic acid

An improved method of recovering a palladium catalyst from a liquid reaction mixture having been produced by oxidative coupling reaction of an aromatic compound in the presence of a catalyst containing palladium(II) salt is disclosed. The improved method comprises heating the liquid reaction mixture under stirring at a temperature of 180.degree. to 280.degree. C. in an atmosphere containing hydrogen gas at a partial pressure of 5 to 60 kg/cm.sup.2 whereby reducing the catalyst in the reaction mixture and precipitating a metallic palladium from the reaction mixture.

Growing community of inventors

Ube, Japan

Akira Ishikawa