METHOD OF RECOVERING COPPER-VANADIUM CATALYST FROM MOTHER LIQUORS IN ADIPIC ACID PRODUCTION

摘要

FIELD: industrial organic synthesis. SUBSTANCE: invention relates to synthesis of adipic acid via oxidation of cyclohexanol and/or cellohexanone with nitric acid in presence of copper-vanadium catalyst. The latter is commonly recovered by concentrating mother liquors using evaporation until residue containing dicarboxylic acids $$$, copper and vanadium salts, non-reacted nitric acid and water is obtained followed by isolating catalyst and returning it into the oxidation step, whereupon dicarboxylic acids $$$ are isolated at lowered temperature. Invention consists in that mother liquor evaporated to 65-75 vt % concentration of dicarboxylic acids $$$ is mixed with mother liquor from dicarboxylic acids $$$ crystallization step observing weight ratio 1 to 1-1.5, respectively. Resulting suspension is crystallized at temperature below -10 C, preferably from -10 to - 15 C, wet crystals of dicarboxylic acids $$$ are separated, and mother liquor obtained is divided into two streams, one of which is used to dilute the deposit and the other is returned into oxidation step. EFFECT: simplified and enhanced catalyst recovery; utilized mixture of dicarboxylic acids $$$ 1 dwg, 1 tbl