Amine-based extractants for isolation of carboxylic acids from complex, biobased process streams

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Carboxylic acids are important biobased bulk chemicals and can be produced via fermentation of carbohydrate containing materials. Hence, a variety of raw materials can be used for carboxylic acid production. With respect to the biorefinery concept, also waste materials, such as process residues, can be utilized. However, isolation of carboxylic acids from such process streams is challenging because of complex stream compositions and low solute concentrations. Reactive liquid-liquid extraction (LLE) is a widely investigated isolation method for carboxylic acids because of its simple operation, ease of automation, and low energy demand. Further, it enables in situ acid extraction and simultaneously regulates the pH value in the fermenter. One drawback when applying LLE to complex process streams is unwanted crud formation, which leads to solvent phase loss and hinders phase separation. Crud formation is for example influenced by the composition of the solvent phase.
Here, we demonstrate the isolation of lactic and acetic acid from silage press juice. Silage is produced by uncontrolled fermentation and, hence, represents a highly complex mixture. In order to improve the processability of the silage press juice, centrifugation, dilution with water, and filtration are applied. The resulting mixture contains 0.43 mol/L lactic acid and 0.054 mol/L acetic acid at a dry matter content of 13 wt%. In the next step, two-phase reactive LLE experiments are carried out in tempered separation funnels at 25 and 50 °C using different amine-based extractants mixed with disparate modifiers and diluents. Besides a high extraction efficiency, a low crud formation is targeted. Finally, a back-extraction is performed using NaOH or NaHCO3 as stripping phase.
The results show that an extraction efficiency of 25-40 % was reached for lactic acid using dioctylamine, trioctylamine or Aliquat336 as reactive extractant; in case of acetic acid, an efficiency of 42-57 % was achieved. Further, crud formation in the extraction step was reduced from 40 to 3-9 vol%. The back-extraction reached an efficiency up to 98 % for both acids without any crud formation. In conclusion, reactive LLE is an efficient method for the isolation of carboxylic acids from complex, biobased process streams. Further, unwanted crud formation can be reduced by adjustment of the solvent phase composition.
Original languageEnglish
Publication statusPublished - 3 Jun 2022
EventInternational Conference on Renewable Resources and Biorefineries: RBB 2022 - Bruge, Belgium
Duration: 1 Jun 20223 Jun 2022


ConferenceInternational Conference on Renewable Resources and Biorefineries

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