Abstract: Biphenyl-4,4'-dicarboxylic acid is prepared by isolating a mixture of diisopropylbiphenyls from a reaction mixture obtained by reacting biphenyl with propylene, crystallizing 4,4'-diisopropylbiphenyl from the mixture of diisopropylbiphenyls, and oxidizing 4,4'-diisopropylbiphenyl or an oxidation intermediate thereof with molecular oxygen in the presence of an oxidation catalyst, which comprises a cobalt catalyst and/or manganese catalyst, in a solvent containing at least 50 wt. % of an aliphatic mono- carboxylic acid having up to 3 carbon atoms.

Abstract: Disclosed in the present invention is a process for producing 2,6-naphthalenedicarboxylic acid comprising oxidizing 2,6-diisopropylnaphthalene or its partially oxidized intermediate with molecular oxygen in a solvent containing at least 50% by weight of an aliphatic monocarboxylic acid, having not more than three carbon atoms, in the presence of a catalyst composed of (i) a heavy metal comprising cobalt and/or manganese and (ii) bromine, and a salt of an inorganic acid having an acid dissociation constant Ka smaller than 1.34.times.10.sup.-5 (at 25.degree. C.) and a vapor pressure lower than that of the aliphatic monocarboxylic acid used as the solvent. According to the process of this invention, 2,6-naphthalenedicarboxylic acid of high bulk density can be obtained in a high yield and with high purity.

Abstract: Disclosed herein is a process for producing a highly pure produce of 2,6-naphthalenedicarboxylic acid in a large quantity at a moderate price by oxidizing 2,6-diisopropylnaphthalene while using a water-soluble salt of cobalt, a water-soluble salt of maganese or a mixture thereof, a water-soluble salt of cerium and a bromine compound as the catalyst of the oxidation.

Abstract: Disclosed herein is a process for producing 2,6-naphthalenedicarboxylic acid together with trimellitic acid comprising oxidizing 2,6-diisopropylnaphthalene with molecular oxygen in the presence of a catalyst comprising a heavy metal(s) and bromine.

Abstract: Disclosed herein is a process for producing 2,6-naphthalenedicarboxylic acid, comprising (1) oxidizing 2,6-diisopropylnaphthalene in a lower fatty acid as a solvent in the presence of a catalyst comprising a water-soluble cobalt salt and/or a water-soluble manganese salt in an amount of at least 0.5 gram-atom of Co and/or Mn to 1 mol of 2,6-diisopropylnaphthalene by an oxygen-containing gas, thereby obtaining isopropylnaphthalene-monocarboxylic acid and (2) further oxidizing the thus obtained 6-isopropyl-2-naphthoic acid in the lower fatty acid in the presence of the catalyst comprising a water-soluble cobalt salt and/or a water-soluble manganese salt in an amount of from 0.0025 to 0.12 gram-atom to 1 mol of 6-isopropyl-2-naphthoic acid by the oxygen-containing gas, thereby obtaining 2,6-naphthalenedicarboxylic acid.