REGENERATION OF CARBOXYLIC-ACID AMINE EXTRACTS BY BACK-EXTRACTION WITH AN AQUEOUS-SOLUTION OF A VOLATILE AMINE

Tertiary amines are effective extractants for the recovery of carboxylic acids from aqueous solution. An approach for regeneration and product recovery from such extracts is to back-extract the carboxylic acid with a water-soluble, volatile tertiary amine, such as trimethylamine. The resulting trimethylammonium carboxylate solution can be concentrated and thermally decomposed, yielding the product acid and the volatile amine for recycle. Equilibrium data are presented that show near-stoichiometric recovery of carboxylic acids from amine extracts. For fumaric and succinic acids, partial evaporation of the aqueous back-extract decomposes the carboxylate and yields the acid product in crystalline form. The decomposition of aqueous solutions of trimethylammonium lactates stops short of forming the acid product, because of its greater water solubility and tendency for self-association. Methods of further purifying the crystals are evaluated, along with processing implications of the results.