Rapid room temperature solubilization and depolymerization of polymeric lignin at high loadings

The relatively poor solubility of lignin in most pretreatment solvents remains one of the biggest challenges in lignin valorization to improve overall biorefinery economics. In this work, rapid room temperature solubilization of lignin at high solid loadings (>30 wt%) can be easily achieved in a single step using ethylene glycol (EG). The solubilized lignin can be rapidly and quantitatively recovered with the addition of ethanol. The computational and nuclear magnetic resonance (NMR) spectroscopic studies confirm that strong hydrogen bond interactions between EG and the free hydroxyl groups present in lignin contribute to the lignin dissolution. In addition, hydrogen peroxide mediated depolymerization of the dissolved lignin at a low temperature (80°C) was tested and the effect of EG molecules on depolymerization of lignin was also theoretically studied. The findings of this work provide mechanistic insights of hydrogen bond interactions in high lignin solubilization and valorization.