PROCESS FOR PREPARING PHTHALIC ACID ISOMERS HAVING HIGH PURIFICATION DEGREE Russian patent published in 1995 - IPC

FIELD: as a monomer for the production of polymeric materials. SUBSTANCE: the product: terephthalic, isophthalic and phthalic acids having high purity degree. No hydrogenation stage is used for purification purposes. Reagent 1: a xylene isomer. Reagent 2: an oxygen-containing gas. Reaction conditions: after the first and second oxidation stages, the precipitate is separated from the solvent and then treated with a recycling solvent. The resulting slurry is heated to high temperature to extract the impurities, then cooled and treated with air and catalysts at the third oxidation stage. Distinctive features: a modified catalytic system comprising a conventional Co-Mn-Br catalyst and nickel, chromium, zirconium or cerium additives individually or in admixture with one another, thus promoting selective acceleration of the oxidation reaction. Preheating and a special method of feeding the reaction mixture afford a uniform oxidation rate within the entire reaction volume, moderate temperatures and a relatively short reaction period. EFFECT: more efficient preparation process. 4 cl, 1 dwg, 1 tbl