The chemistry of ammonium-based ionic liquids in depolymerization process of lignin

In the present study, an ammonium-based ionic liquids (ILs)-assisted green method is developed to selectively depolymerize lignin into the valuable phenolic compounds. The influence of the selected ammonium-based ionic liquids, DIPEAA and DIPEAO, on depolymerization of the alkali lignin is investigated by using chromatographic (gel permeation chromatography (GPC) and GC-MS) and various spectroscopic (FTIR, 1H NMR, and 13C NMR) techniques. The results from those series of measurements strongly suggest that these ILs (DIPEAA and DIPEAO) are highly suitable to use not only as a solvent but also as a catalyst in the depolymerization of the alkali lignin. The effects of the operating parameters including reaction conditions (temperature and elapsed time of reaction) and hydrophobicity of the ionic liquids, on the efficiency of the depolymerization process are discussed. In addition, the mechanism of the investigated ILs-assisted lignin depolymerization process is also proposed.