Novel Intensified Back Extraction Process for Itaconic Acid: Toward in Situ Product Recovery for Itaconic Acid Fermentation

Itaconic acid (IA), an unsaturated dicarboxylic acid produced by fermentation, is a promising alternative to petrochemical-based monomers as a building block for plastics, resins, and synthetic fibers. Efficient recovery of IA from aqueous fermentation broth was previously achieved by amine-based reactive extraction (RE) systems. In the present work, several back extraction methods were tested in order to recover IA from four different RE solutions, three based on trioctylamine and the diluents methyloctanoate, pentylacetate, and 1-octanol, and one based on N-methyldioctylamine and the diluent 1-octanol. Conventional back extraction methods using a temperature swing, NaOH, or tertiary volatile amines were applied and tested at different conditions. Especially with tertiary volatile amines, good back extraction efficiencies were achieved. As an intensified approach, in addition a novel back extraction-conversion method was developed to recover the itaconic acid in the form of methyl-esters. This approach was based on noncatalyzed in situ esterification with high temperature-pressure methanol (HTPM) allowing a continuous processing. Reaction temperature, residence time, pressure, and methanol excess were investigated. At 200-250 °C and a residence time of 10-20 min, with methanol dosed at a similar weight as the RE-layer, ester formation of >80 mol % could be obtained with a continuous esterification process. This latter method can be a suitable alternative technique for standard back extraction procedures, aiming at an easy recovery of the IA ester through distillation, followed by a direct polymerization to bioplastics.