Abstract: A process for producing highly pure isophthalic acid which comprises (a) carrying out liquid phase oxidation of an m-dialkyl benzene with molecular oxygen in an acetic acid solvent in the presence of a heavy metal catalyst to form crude isophthalic acid, (b) contact-treating the resulting crude isophthalic acid with a noble metal catalyst belonging to the Group VIII of the Periodic Table supported by activated carbon in the presence of hydrogen, and then (c) separating the deposited isophthalic acid crystal and (d) filtration-treating the separated mother liquor and (e) recirculating the mother liquor thus treated into the liquid phase oxidation step (a) for reusing as a solvent in step (a) is disclosed.

Abstract: A process for producing isophthalic acid by oxidation of m-xylene with an oxygen-containing gas in a hydrous acetic acid solvent in the presence of a cobalt/manganese/bromine system catalyst, the process being capable of industrially advantageously producing high-purity isophthalic acid having excellent whiteness, the process comprising (1) a step of carrying out an oxidation reaction in a main oxidation reactor under specified ranges of a catalyst concentration, a reaction temperature and an oxygen concentration in a discharge gas such that the concentration of 3-carboxybenzaldehyde becomes 500 to 10,000 ppm, (2) a step of further carrying out an oxidation reaction in a post oxidation reactor such that the concentration of 3-carboxybenzaldehyde becomes 100 to 800 ppm, separating crude isophthalic acid, evaporating remaining mother liquor and recovering acetic acid, and (3) mixing the crude isophthalic acid with purified acetic acid, stirring the resultant mixture at 100.degree. C.

Abstract: Terephthalic acid with a high purity for direct polymerization with glycols is produced by oxidizing p-tolualdehyde with a gas containing molecular oxygen in water as a solvent in the presence of bromine ions in an oxidation reactor using zirconium as a reactor material.

Abstract: Terephthalic acid of high purity is continuously produced in a high yield by oxidizing p-tolualdehyde with a molecular oxygen-containing gas in the presence of bromine ions as a catalyst in a water solvent, contacting the resulting slurry solution containing crude terephthalic acid with an ascending stream of high temperature water of 180.degree.-320.degree. C., and withdrawing the water solvent together with the ascending stream of high temperature of water upwardly, while settling down crystalline terephthalic acid through the ascending stream of high temperature water and withdrawing the crystalline terephthalic acid together with a portion of the high temperature water downwardly.

Abstract: In the production of phthalic acid by oxidizing, in a liquid phase, tolualdehyde with molecular oxygen or a gas containing the molecular oxygen in the presence of heavy metal salt containing a Mn salt, especially both Mn and Co salts, and a bromine compound, using a lower aliphatic monocarboxylic acid as a reaction solvent, a blackening of phthalic acid is effectively prevented by conducting the oxidation of tolualdehyde in the presence of an alkylbenzene in an amount satisfying the following formula (1);M.ltoreq.-0.15A.sup.2 +15A+40 (1)wherein M is a Mn atom concentration in.ppm by weight on the basis of the reaction solution, and A is an amount in % by weight of the alkylbenzene added on the basis of the total of tolualdehyde and said alkylbenzene, and is in a range of from more than 0 to 50 inclusive.

Abstract: Terephthalic acid is produced by oxidizing, in a liquid phase, p-tolualdehyde with a gas containing molecular oxygen, for example, air, in the presence of a catalyst consisting each of (1) a manganese compound, (2) a cobalt compound, (3) a bromine compound, and (4) at least one compound selected from the group consisting of chromium compounds, iron compounds, nickel compounds and compounds of metallic elements belonging to the lanthanide series, using a lower aliphatic monocarboxylic acid as a solvent.