Lignin derived hydrophobic deep eutectic solvents as sustainable extractants

Solvent innovation has become a central task for improving the sustainability of chemical processes1. Deep eutectic solvents (DESs) emerge as environmentally friendly alternatives to toxic and volatile organic solvents. One appealing aspect for DESs is that they can be synthesized using naturally occurring compounds from biomass. Herein, we prepared novel hydrophobic DESs based on lignin derivatives and characterized their physicochemical properties including density, viscosity, and thermal behavior. The results showed that five lignin-derived hydrophobic DESs made from menthol, thymol, and 2,6-dimethoxyphenol were promising as green solvents due to their low viscosities and environmentally friendly constituents. To evaluate the potential application of these DESs, liquid-liquid extraction was performed to recover the typical biofuel fermentation products including acetone, ethanol, n-butanol, and isopentanol from aqueous solutions. High distribution co-efficients, selectivity, and recovery rates for acetone, n-butanol, and isopentanol were achieved with the thymol: 2,6-dimethoxyphenol DESs. Moreover, molecular dynamic simulations were conducted to investigate the DES molecular interactions and formation mechanism. This work demonstrates the potential of lignin derived hy-drophobic DESs for applications as sustainable extraction media.

Automated summary

Solvent innovation is crucial for enhancing the sustainability of chemical processes. Deep eutectic solvents (DESs) have emerged as environmentally friendly alternatives to toxic and volatile solvents. In this study, hydrophobic DESs derived from lignin were synthesized and their physicochemical properties were characterized. The DESs showed promise as green solvents due to their low viscosity and environmentally friendly constituents. Liquid-liquid extraction experiments revealed high extraction efficiency for biofuel fermentation products using specific DES compositions. Molecular dynamic simulations provided insights into the DES molecular interactions and formation mechanism. This work highlights the potential of lignin-derived hydrophobic DESs as sustainable extraction media.