Ionic liquid

Carbon-13 NMR

Organic chemistry

Dimethyl sulfoxide

Dissolution

Kraft process

Engineering

Solubility

Catalysis

Ionic bonding

Inorganic chemistry

Chemistry

Solvent

Lignin

Kraft paper

Chemical engineering

Journal of Wood Chemistry and Technology

This study examined the application of select ionic liquids (ILs) as aprotic green solvents for lignin. Dissolution experiments were carried out employing lignin isolated from pine kraft pulp. Up to 20 wt% lignin could be dissolved in [hmim][CF3SO3], [mmim][MeSO4] and [bmim][MeSO4]. For the [bmim]+‐containing ionic liquids, the order of lignin solubility for varying anions was: [MeSO4]−>Cl−∼Br−⋙[PF6]−, indicating that the solubility of lignin was principally influenced by the nature of the anions. Ionic liquids containing large, non‐coordinating anions [PF4]− and [PF6]− were unsuitable as a solvent for lignin. 13C nuclear magnetic resonance (NMR) analyses of lignin and model compounds showed that 13C signals using ionic liquid as a solvent were shifted up‐field by δ 0.1 to 1.9 ppm in comparison to 13C NMR data acquired using dimethyl sulfoxide (DMSO) as the solvent.

Ionic Liquid as a Green Solvent for Lignin