Investigation into selective separation of lignin in novel deep eutectic solvent

In recent years, choline, a novel kind of bio-based ILs (Ionic Liquids) used as a good lignin solvent, has been paid more and more attention to. In this paper, based on Hansen's theory of solubility, a novel ionic liquid analogue named DES (Deep Eutectic Solvent), in which lactic acid (LA) and choline chloride (ChCl) were respectively used as the donor and the acceptor of hydrogen bonds, was designed to separate lignin. Then, the dissolution results of lignin affected by the molar ratio of ChCl to LA, the reaction temperature and the interaction time were investigated by experiments. It was found that the dissolution rate of lignin reached the optimal 90.1% and the purity of regenerated lignin reached 96.3% at a ChCl-to-LA molar ratio of 1:9, a reaction temperature 90℃ and a reaction duration of 12 h. The results of UV-Vis spectroscopy and FT-IR spectroscopy show that the lignin in the wood powders is greatly removed after DES treatment. XRD results show that the structure of cellulose in the pretreated wood powders is barely damaged. 13C NMR results indicate that the regenerated lignin is mainly composed of syringyl, guaiacyl and a little p-hydroxylphengl. Moreover, ion chromatography results show that only a small amount of holocellulose is dissolved in the mixed solution. © 2016, Editorial Department, Journal of South China University of Technology. All right reserved.