Glycerol-Derived Solvents for Tractable Organosolv Extraction of Softwood Lignins

• Published in: ACS sustainable chemistry & engineering 2024-10, Vol.12 (41), p.15089-15102
• Main Authors: Agwu, Kelechi A., Ekeoma, Bernard C., Enguita, Jayna M., Daymude, Jacob W., Bara, Jason E., Sheehan, James D.
• Format: Article
• Language: English
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.4c04801

In the present study, glycerol-derived ethers (GDEs) are evaluated as green solvents to facilitate organosolv extraction of lignins from softwood biomass. GDEs assessed in the present investigation consist of glycerol skeletons etherified with alkyl constituents (e.g., methyl, ethyl), including 1,3-glycerol diethers and 1,2,3-glycerol triethers. GDEs are derived from glycerol, a high-volume byproduct produced by the biodiesel industry. In comparison to glycerol, GDEs are ∼3 orders of magnitude less viscous while maintaining high boiling points (>160 °C), facilitating improved processability and extraction of lignins under mild temperatures and pressures. The influence of organosolv conditions, specifically temperature (120–180 °C), batch holding time (10–240 min), Brønsted acid concentration, and solvent composition on the extraction of lignins from softwood feedstocks are evaluated. Under optimal conditions (150 °C, 60 min), over 70 wt % of lignins are extracted from softwood biomass. More severe conditions (e.g., 160 °C, 60 min; 180 °C, 60 min) promoted higher delignification (80–90 wt %) but at the expense of lower pulp yields (