Lignin Structure and Aggregation Behavior in a Two-Component Ionic Liquid Solvent System
Susanne Bylin,
Tyrone Wells,
Qining Sun,
Art Ragauskas,
Hans Theliander
Affiliations
Susanne Bylin
Chalmers University of Technology, Department of Chemical and Biological Engineering, Division of Forest Products and Chemical Engineering and Wallenberg Wood Science Center, The Royal Institute of Technology, SE-100 44 Stockholm Sweden
Tyrone Wells
Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden, Division of Forest Products and Chemical Engineering and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA
Qining Sun
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA and Institute of Paper Science and Technology, Georgia Institute of Technology, Atlanta, GA, 30332, USA
Art Ragauskas
School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA, 30332, USA and Institute of Paper Science and Technology, Georgia Institute of Technology, Atlanta, GA, 30332, USA
Hans Theliander
Chalmers University of Technology, Department of Chemical and Biological Engineering, Division of Forest Products and Chemical Engineering and Wallenberg Wood Science Center, The Royal Institute of Technology, SE-100 44 Stockholm Sweden
Ionic liquids are of potential interest in the processing of lignocellulosic biomass. In this study, the ionic liquid co-solvent system of 1-methylimidazole (MIM) and 1-ethyl-3-methyl-imidazolium acetate (EMIMAc) was used to solvate LignoBoost lignin fractionated from black liquor obtained from a kraft paper mill. Lignin ethanol-precipitated (LEP) and ethanol-soluble (LES) fractions were characterized via gel permeation chromatography (GPC) and 13C- and 31P-nuclear magnetic resonance spectroscopy (NMR) to determine structural characteristics and their relationship to polymer solubility in the system. Polymer integrity and solubility were optimal at ~20% lignin loading (w/w). Results showed that LEPs were generally of higher apparent molecular weight (Mw) and enriched with condensed/aliphatic ether linkages and aliphatic hydroxyls. The LESs had a lower apparent Mw and were enriched with carboxylic and phenolic groups. This newly gained knowledge on lignin fractionation and aggregation in the present solvent system provides future opportunities for tuning fractionation/extraction to suit a specific biomass-derived product, e.g., carbon fibers.
