Abstract: A process for continuously producing high purity terephthalic acid, in particular, useful for direct polymerization, which comprises continuously introducing p-dialkylbenzene as a feed material together with a solvent and an oxidation catalyst into a reactor, subjecting the p-dialkylbenzene to a liquid phase oxidation with oxygen in the reactor to produce terephthalic acid, continuously or intermittently introducing the reaction mixture containing terephthalic acid thus produced into a stabilizer, and oxidizing the reaction mixture in the stabilizer for an extended period of time with a molecular oxygen containing gas of a low oxygen concentration at a temperature and pressure the same as or lower than those in the oxidation reaction while keeping the volume change of the contents in the stabilizer below about 30% by volume of the contents of the stabilizer.

Abstract: A process for producing an aromatic carboxylic acid by liquid-phase oxidizing an alkylbenzene with a molecular oxygen-containing gas in a lower aliphatic carboxylic acid solvent in the presence of a heavy-metal-bromine oxidation catalyst, in which the oxidation reaction is conducted using a material containing as inorganic elements only cobalt, manganese, and bromine as the catalyst components and while withdrawing from the reaction system, at least partially, the condensed liquid of a gaseous mixture discharged from the top of the reactor during the reaction and maintaining the water content of the reaction system below a definite level by introducing fresh solvent (or, preferably, the solvent recovered as a side cut fraction by distilling the condensed liquid) in an amount corresponding to the amount of the solvent withdrawn contained in the condensed liquid, and a reaction mother liquor which is formed by separating the aromatic carboxylic acid from the reaction mixture withdrawn from the reactor is recycl

Abstract: A method for recovering a heavy metal oxidation catalyst used in a liquid-phase oxidation process for producing terephthalic acid from the residue of the reaction mother liquor by stirring the residue together with water in the presence of molecular oxygen and a sulfur compound, subjecting the extracted mixture to a solid-liquid separation to separate the solid impurities, adding the aqueous solution containing the oxidation catalyst to an alkali metal or ammonium carbonate or an aqueous solution of an alkali metal or ammonium carbonate while maintaining the temperature of the system at about 26.degree.C to 70.degree.C, and recovering the heavy metal catalyst as a carbonate precipitate having high purity and good filterability and washability.