TY - BOOK
T1 - Application of a Natural Deep Eutectic Solvent as a Modifier in the Reactive Extraction of Lactic Acid from Bio-Based Process Streams – Sweet Sorghum Silage Press Juice as an Example
AU - Demmelmayer, Paul
PY - 2024/6/27
Y1 - 2024/6/27
N2 - The transition from a linear, fossil-based economy to a circular, bio-based approach is a necessity to reduce resource consumption, environmental pollution, and mitigate the associated climate change. Biorefineries are a pivotal component in this transition by utilizing renewable resources and residues to produce a variety of products. Lactic acid, a bio-based bulk chemical, is mainly produced by carbohydrate fermentation. However, the isolation of lactic acid from fermentation broths is complex and poses environmental issues. This thesis investigates reactive liquid-liquid extraction as an isolation method for lactic acid using sweet sorghum silage as a representative bio-based process stream. To enhance the sustainability of the extraction process, a natural deep eutectic solvent is examined as a green alternative to fossil-based modifiers. The application of a thymol-menthol-based natural deep eutectic solvent as the modifier was examined in single-stage phase equilibrium measurements. Using tri-n-octylamine as the extractant, the natural deep eutectic solvent showed a lactic acid extraction efficiency of 48.7 ± 0.7%, which is higher as compared to the 35.0 ± 0.8% obtained with the fossil-based modifier 1-octanol. Additionally, using the natural deep eutectic solvent as the modifier resulted in a higher lactic acid extraction efficiency at pH values between five and seven, which is promising because this is the common pH range of lactic acid fermentations. Continuous lactic acid extraction from microfiltered sweet sorghum silage press juice was examined in an agitated and continuously operated extraction column. The natural deep eutectic solvent showed low crud formation, good phase separation, and a similar hydraulic performance as the benchmark modifier 1-octanol when using tri-n-octylamine as the extractant. The continuous extraction process was limited by the rising pH value of the aqueous phase. In three-stage cross-current extraction experiments, it was found that the lactic acid extraction efficiency can be increased from 37.0 ± 0.4 to 76.2 ± 0.9% by continuous pH adjustment with mineral acids. However, further investigations showed that mineral acids are co-extracted by tri-n-octylamine. The highest co-extraction was observed for phosphoric acid and the lowest for nitric acid. The estimation of the economic feasibility of the lactic acid isolation from sweet sorghum silage showed an improved performance with the thymol-menthol-based natural deep eutectic solvent as the modifier compared to 1-octanol. However, the resulting retail price of the produced 80 wt% lactic acid solution makes process optimizations necessary. In conclusion, the results show the applicability of a thymol-menthol-based natural deep eutectic solvent in continuous liquid-liquid extraction processes. This is promising for the future as renewable solvents are required as alternatives to fossil-based solvents.
AB - The transition from a linear, fossil-based economy to a circular, bio-based approach is a necessity to reduce resource consumption, environmental pollution, and mitigate the associated climate change. Biorefineries are a pivotal component in this transition by utilizing renewable resources and residues to produce a variety of products. Lactic acid, a bio-based bulk chemical, is mainly produced by carbohydrate fermentation. However, the isolation of lactic acid from fermentation broths is complex and poses environmental issues. This thesis investigates reactive liquid-liquid extraction as an isolation method for lactic acid using sweet sorghum silage as a representative bio-based process stream. To enhance the sustainability of the extraction process, a natural deep eutectic solvent is examined as a green alternative to fossil-based modifiers. The application of a thymol-menthol-based natural deep eutectic solvent as the modifier was examined in single-stage phase equilibrium measurements. Using tri-n-octylamine as the extractant, the natural deep eutectic solvent showed a lactic acid extraction efficiency of 48.7 ± 0.7%, which is higher as compared to the 35.0 ± 0.8% obtained with the fossil-based modifier 1-octanol. Additionally, using the natural deep eutectic solvent as the modifier resulted in a higher lactic acid extraction efficiency at pH values between five and seven, which is promising because this is the common pH range of lactic acid fermentations. Continuous lactic acid extraction from microfiltered sweet sorghum silage press juice was examined in an agitated and continuously operated extraction column. The natural deep eutectic solvent showed low crud formation, good phase separation, and a similar hydraulic performance as the benchmark modifier 1-octanol when using tri-n-octylamine as the extractant. The continuous extraction process was limited by the rising pH value of the aqueous phase. In three-stage cross-current extraction experiments, it was found that the lactic acid extraction efficiency can be increased from 37.0 ± 0.4 to 76.2 ± 0.9% by continuous pH adjustment with mineral acids. However, further investigations showed that mineral acids are co-extracted by tri-n-octylamine. The highest co-extraction was observed for phosphoric acid and the lowest for nitric acid. The estimation of the economic feasibility of the lactic acid isolation from sweet sorghum silage showed an improved performance with the thymol-menthol-based natural deep eutectic solvent as the modifier compared to 1-octanol. However, the resulting retail price of the produced 80 wt% lactic acid solution makes process optimizations necessary. In conclusion, the results show the applicability of a thymol-menthol-based natural deep eutectic solvent in continuous liquid-liquid extraction processes. This is promising for the future as renewable solvents are required as alternatives to fossil-based solvents.
M3 - Doctoral Thesis
ER -