Purification of Fermentation-Derived Acetic Acid By Liquid−Liquid Extraction and Esterification

Abstract

Liquid−liquid extraction and esterification were investigated for the purification of acetic acid. With model solutions, a solvent system containing equal volumes of Alamine-336 and 2-ethyl-1-hexanol resulted in 85% extraction efficiency when the pH of the broth was below 3.5. At higher pH, Aliquat-336 could extract higher amounts. With the fermentation broth (pH 6−7), direct acidification with sulfuric acid gave yields of 66% at pH 3.4. Lowering the pH by bipolar electrodialysis was more effective and gave higher yields of 85%. Esterification with ethyl and butyl alcohols was optimum at a molar ratio of 3:1 alcohol to acetic acid. With model solutions (no water present), yields were 65−75% of theoretical. However, the large amount of water present in the fermentation broth inhibited esterification, giving yields of only 5−20%.