Extractant screening for bio-based recovery of carboxylic acids

Production of chemicals through environmentally benign processes requires effective methods for the recovery of typically highly hydrophilic products from the complex fermentation broth. Carboxylic acids, which are of high interest as building blocks for biodegradeable plastics, can be produced via fermentation. Their recovery is often done through extraction using tertiary amines. However, in order to become an economically viable alternative for traditional chemical synthesis, this process needs to be improved. This paper reports an extractant screening study for the model solutes lactic acid and succinic acid, aiming at better process efficiency. A range of extractants were evaluated, including amines, amides, superbases, guanidines and N-oxides. Octanol, 2-octyl- 1-dodecanol and heptane were used as diluents. Batch extraction experiments were done under compareable conditions (20 % wt extractant in octanol, 1.2% wt acid, ambient temperature) to evaluate the performances of the various extractants. The highest distributions (D) were observed for tertiary amines; D = 30 for lactic acid and D = 45 for succinic acid. The extraction performance with N-oxides and superbases was in both cases negligible (