Sustainable and Energy-Efficient Fractionation of Lignocellulosic Biomass with Choline-Based Deep Eutectic Solvents

Deep eutectic solvents (DESs), recognized as economical and environmentally friendly green solvents, are employed for the fractionation of lignocellulosic biomass with varying degrees of effectiveness. This work compared choline chloride/urea (ChCl/Ur), choline chloride/lactic acid (ChCl/LA), and lactic acid (LA) for poplar fractionation. The interactions between the solvents and the components of biomass were investigated based on the chemical structure of the solvent constituents. The efficiency for the fractionation is hypothesized to depend on the availability of acidic or alkaline functional groups within the solvent constituents and relate to the solvent-component affinity. A promising water-regulated DES system, choline hydroxide/urea (ChOH(H₂O)/Ur), was discovered for the fractionation of lignocellulosic biomass. This system achieved component removal rates exceeding 40% relative to the raw poplar at 60°C and enabled efficient fractionation of other biomass from different sources. The extracted components exhibited unique properties, retaining relatively intact structures and requiring no further purification. This study contributes to a deeper understanding of how solvent components influence the interactions between DESs and biomass components, providing valuable insights for designing and selecting novel solvent systems for the green comprehensive utilization of lignocellulosic biomass resources.