Switchable Ionic Liquids as Delignification Solvents for Lignocellulosic Materials

The transformation of lignocellulosic materials into potentially valuable resources is compromised by their complicated structure. Consequently, new economical and feasible conversion/fractionation techniques that render value‐added products are intensely investigated. Herein an unorthodox and feasible fractionation method of birch chips ( B. pendula ) using a switchable ionic liquid (SIL) derived from an alkanol amine (monoethanol amine, MEA) and an organic super base (1,8‐diazabicyclo‐[5.4.0]‐undec‐7‐ene, DBU) with two different trigger acid gases (CO 2 and SO 2 ) is studied. After SIL treatment, the dissolved fractions were selectively separated by a step‐wise method using an antisolvent to induce precipitation. The SIL was recycled after concentration and evaporation of anti‐solvent. The composition of undissolved wood after MEA‐SO 2 ‐SIL treatment resulted in 80 wt % cellulose, 10 wt % hemicelluloses, and 3 wt % lignin, whereas MEA‐CO 2 ‐SIL treatment resulted in 66 wt % cellulose, 12 wt % hemicelluloses and 11 wt % lignin. Thus, the MEA‐SO 2 ‐SIL proved more efficient than the MEA‐CO 2 ‐SIL, and a better solvent for lignin removal. All fractions were analyzed by gas chromatography (GC), Fourier transform infrared spectroscopy (FT‐IR), 13 C nuclear magnetic resonance spectroscopy (NMR) and Gel permeation chromatography (GPC).