METHOD OF PRODUCING PURE ISOPHTHALIC ACID AND BY-PRODUCTS FROM XYLENE FRACTIONS Russian patent published in 2011 - IPC C07C63/24 C07C51/265 C07C51/42 C07C51/43 

FIELD: chemistry.

SUBSTANCE: invention relates to a method of producing isophthalic acid and other by-products - terephthalic and benzoic acid, based on oxidation of a mixture of xylene isomers and monoalkylbenzenes contained therein with an oxygen-containing gas in the medium of acetic acid in the presence of a catalyst which contains heavy metal salts and halides at high temperature and pressure to a defined degree of conversion of said isomer mixtures to isophthalic acid and by-products, followed by purification and separation of isophthalic acid and by-products via re-crystallisation in a solvent, wherein said oxidation process is carried out in two steps with increasing concentration of the Co-Mn catalyst on the steps, promoted by halides in form of HBr in equimolar ratio to metals in the range of 800-1200 ppm at temperature 150-200°C and discrete stepwise reduction of pressure in the range of 1.8-1.2 MPa with pressure drop gradient between steps of 0.2-0.6 MPa; purification and separation of the mixture of isophthalic and by-product benzene-carboxylic acids is carried out in two steps by extracting impurities via re-crystallisation in acetic acid at temperature 140-230°C at the first step followed by extraction of the purified binary system of isophthalic and terephthalic acid and separation thereof at the second step via dissolution in water at temperature 220-230°C and stepwise selective crystallisation and extraction of terephthalic acid at temperature 180-195°C, and isophthalic acid at temperature 60-100°C.

EFFECT: improved quality of isophthalic acid and by-products and high efficiency of the synthesis process.

10 cl, 12 ex, 3 tbl