HIGH-PURITY ISOPHTHALIC ACID PRODUCTION PROCESS Russian patent published in 1999 - IPC

FIELD: industrial organic synthesis. SUBSTANCE: isophthalic acid is prepared by combination of two interrelated processes of liquid-phase catalytic oxidation of m-xylene with oxygen-containing gas in acetic acid medium followed by recrystallization of crude product. Oxidation process is carried out in two in-series disposed reactors within temperature range 180-198 C in presence of catalyst consisting of manganese and cobalt acetates and bromine compound mixture (HBr). Catalyst is further supplemented by chlorine in the form of lithium chloride or its mixture with manganese and cobalt chlorides as well as hydrogen chloride. Cl/Br atomic ratio is 1: (1-1.9). Duration of mixing reactants in oxidation zone is 12 s, and residual concentration of m-carboxybenzaldehyde in oxidation products is 0.15-0.25 wt %. Purification of isophthalic acid to remove intermediate and by-products is accomplished by recrystallization from acetic acid and/or water at 185-220 C followed by four-step cooling accompanied by recycling mother solutions after separation of crude and high-purity product. Reaction water is removed from oxidation reactors and crystallizes to achieve optimal composition of acetic acid-water solvent. EFFECT: increased productivity of process and improved quality of product. 4 cl, 1 tbl, 17 ex