METHOD FOR CRYSTALLIZATION OF CARBOXYLIC ACID Russian patent published in 2004 - IPC

FIELD: organic chemistry, chemical technology. SUBSTANCE: invention relates to the improved method for treatment of reaction mixture obtained by direct oxidation of cyclohexane to adipic acid in liquid phase, in solvent, in the presence of catalyst dissolved in the reaction medium. Method involves decantation of two liquid phases: upper nonpolar phase containing unreacted cyclohexane mainly and lower polar phase containing mainly solvent, adipic acid and formed acids, catalyst and some other reaction products and unreacted hydrocarbon. Then method involves distillation lower polar phase or, if necessary, all reaction mixture to obtain distillate containing at least part of the most volatile compounds, such as unreacted cyclohexane, solvent, intermediate reaction products and water, on the one hand, and residue after distillation containing adipic acid and formed carboxylic acids, catalyst, from the other hand. Method involves stage for addition to distillation residue of organic solvent in which solubility of adipic acid is 15 wt. -% or lower at temperature 20 C, or mixture containing at least one organic solvent. Organic solvent is taken among group of organic compounds comprising ether, ketone, ester, nitrile, amide, sulfoxide or carbonate functional groups excepting acetone, halogen-containing, nitrogen-containing or phosphorus- containing organic solvents. After possible filtration of obtained medium crystallization of formed acids is carried out by cooling and/or evaporation of solvent. Method provides preparing adipic acid of high purity degree that can be used for preparing polyamides and other polymers. EFFECT: improved crystallization method. 9 cl, 2 tbl, 7 ex