Abstract: Disclosed is a process for preparing a diphenyl sulfonetetracarboxylic acid, the process comprising oxidizing a tetramethyldiphenyl sulfone with oxygen or an oxygen-containing gas in an aliphatic monocarboxylic acid having 2 to 10 carbon atoms in the presence of a catalyst consisting essentially of a cobalt component, a manganese component and a bromine compound wherein the weight ratio of manganese metal to cobalt metal is in the range of approximately 0.01 to 0.5.

Abstract: Disclosed is a method for purifying a crude diphenylsulfone tetracarboxylic acid which comprises the steps of dissolving a crude diphenyolsulfone tetracarboxylic acid in a solvent mixture of water and acetic acid and recrystallizing the crude to obtain a highly purifed diphenylsulfone tetracarboxylic acid.

Abstract: In preparing a diarylsulfone by condensing sulfuric acid or an aromatic sulfonic acid with an aromatic compound having at least one replaceable hydrogen atom on the aromatic ring, the process of the present invention is characterized in that the condensation reaction is carried out in the presence of at least one catalyst selected from the group consisting of a tungstic acid, molybdic acid and heteropoly acid thereof.

Abstract: This invention provides a process for preparing carboxylic acid, the process comprising subjecting an oxidation product produced by reacting a peroxide with (a) unsaturated aliphatic monocarboxylic acid having at least one unsaturated bond in the carbon chain and containing 6 to 24 carbon atoms or its ester or (b) cyclic and/or acyclic aliphatic olefin having at least one unsaturated bond in the carbon chain to oxidation by oxygen or oxygen-containing gas in the presence of a catalyst comprising (i) at least one heavy metal compound and (ii) at least one member selected from the group consisting of a bromine compound and a chlorine compound.