(169b) Continuous Biocompatible Reactive Extraction Concept for the Purification of Di-Carboxylic Acids from Dilute Aqueous Solutions

Product concentrations for the biocatalytic production of dicarboxylic acids achievable by whole-cell biocatalysis have recently been shown to reach industrial levels. Caused by their high reactivity, dicarboxylic acids are an attractive substance class for the chemical industry and are even described to serve as future platform chemicals. The development of downstream processing (DSP) concepts still is the bottleneck towards an industrial application of dicarboxylic acids from biocatalytic origin.

Reactive extraction (RE) has shown to be applicable as selective and efficient purification step for the direct recovery of dicarboxylic acids from a dilute aqueous solution, with the mechanism of the RE recently described in our previous work [1]. A hydrophobic complex is formed between hydrophilic dicarboxylic acid (cis,cis muconic acid and itaconic acid) and the extractant (tri-n-octylamine) and is extracted into the organic phase. For the recovery of the dicarboxylic acid from the organic RE phase two different strategies have been developed recently: ph-shift and addition of a water soluble amine lead to a full recovery of the acid and allow for a recycle of the organic RE phase containing the extractant.

Within this work batch extraction experiments published previously [1] were transferred into a continuous DSP concept using a 15 stage lab-scale Mixer-Settler setup. The transfer to continuous operation and the scale up (factor 20) in the Mixer-Settler experiments marks a first step to fulfill the requirements for an industrial application. Different process parameters (e.g. mass flow, number of stages for RE and REEX) were investigated with respect to the overall DSP yield achievable. Additionally a recycle of the organic phase (including amines for RE) and a combined RE and REEX was investigated in order to prove the applicability of the developed DSP concept. Stability investigations over the course of up to 12 h at equilibrium state within the Mixer-Settler set up of the system demonstrate the robustness of the presented DSP concept. Aqueous phase after REEX was shown to enable final purification and thus allow for a further development of an in situ DSP concept for dicarboxylic acids from biocatalytic origin.

[1] J. Gorden, T. Zeiner, C. Brandenbusch, Fluid Phase Equilibria, 393 (2015) 78-84