Lignin Depolymerization with Phenol via Redistribution Mechanism in Ionic Liquids

Nowadays, ionic liquids (ILs) have been recognized as a promising way to fractionate biomass. In this study, we discuss how lignin depolymerization was achieved via the redistribution mechanism with phenols in ionic liquids. Two ionic liquids (1-ethyl-3-methylimidazolium xylenesulfonate [emim]­[ABS] and 1-butyl-3-methylimidazolium methylsulfate [bmim]­[MeSO₄]) were selected as a solvent for lignin depolymerization. Before embarking on lignin depolymerization, two selected lignins (organosolv lignin and Klason lignin) were characterized based on their chemical structure and molecular weight. The depolymerized results show that the two lignins (organosolv lignin and Klason lignin) can be extensively depolymerized under oxidative conditions using a Cu/EDTA complex in the presence of a monomeric phenol (4-<i>tert</i>-butyl-2,6-dimethylphenol) that is blocked from oxidative coupling in the <i>ortho</i> and <i>para</i> positions at temperatures of 180 °C