Biomass-Derived γ-Valerolactone-Based Solvent Systems for Highly Efficient Dissolution of Various Lignins: Dissolution Behavior and Mechanism Study

Binary solvent systems consisting of biomass derived gamma-valerolactone (GVL) and one cosolvent (e.g., water, ionic liquids, DMSO, and DMF) were developed as highly efficient systems for dissolution of various types of lignin. It was found that the content of cosolvent in GVL significantly affected the solubility of lignins. More importantly, we first concluded that the relationship between the solubility of lignin and hydrogen bond basicity parameter beta value of solvents depends both on the solvent and on the lignin, which clarifies the existing dispute on this topic. Additionally, the dissolved lignin can be easily recovered by the addition of ethanol without its structure noticeably changing. The as-proposed systems are not only mild and highly efficient but also versatile and flexible (with different components and concentrations), thus adapting to the highly diversity of lignin.