METHOD OF PRODUCING PURE ISOPHTHALIC ACID AND BY-PRODUCTS FROM ISOMERS OF CYMENE AND DIISOPROPYLBENZENE Russian patent published in 2011 - IPC C07C63/24 C07C27/12 C07C51/265 C07C51/43 

FIELD: chemistry.

SUBSTANCE: invention relates to organic and petrochemical synthesis, specifically to the technological process of producing pure isophthalic acid and by-products - terephthalic and formylic acid through oxidation of isomers of cymene or diisopropylbenzene with an oxygen-containing gas in an acetic acid medium in the presence of a catalyst which contains salts of heavy metals and halide compounds at high temperature and pressure to a defined degree of conversion of the said isomer mixtures to isophthalic acid and by-products, followed by separation and purification of pure isophthalic acid and by-products through re-crystallisation in water, where isomers of cymene or diisopropylbenzene are oxidised in two steps at temperature 120-140°C at the first step and 150-160°C at the second step, in conditions where concentration of the Co-Mn catalyst increases in steps in the range 1300-1800 ppm (0.130-0.180%) at the first step, 1800-2400 ppm (0.180-0.240%) at the second step, promoted by halide compounds, reducing pressure in the range 0.9-1.6 MPa with pressure fall gradient between the steps in the range 0.2-0.6 MPa; purification and separation of the reaction mass obtained after oxidation, separation of the solid crystalline product and washing with acetic acid, carrying out re-crystallisation in water with preliminary holding of the aqueous suspension of the isophthalic acid and terephthalic acid mixture at temperature 225-235°C for 10-15 minutes and successive step-by-step extraction of the desired products and by-products: at 150-190°C - extraction of solid terephthalic acid to obtain aqueous mother solution, and at 60-80°C - extraction of solid isophthalic acid form the said mother solution and washing the extracted isophthalic acid with 2-2.5-fold amount of water to obtain isophthalic acid with the following qualities: chromaticity, °H, ≤10 - m-carboxybenzaldehyde [M-CBA], %, ≤0.002 - m-toluic acid [M-TA], %, ≤0.005 - benzoic acid [BA] %, ≤0.005.

EFFECT: efficient method of producing pure isophthalic acid.

2 cl, 2 tbl, 17 ex