Lignin extraction from wood biomass by a hydrotropic solution

Lignin was extracted from different softwood and hardwood materials using sodium xylenesulphonate (SXS) solution as a solvent. Extracted lignin was precipitated from the solvents, washed and freeze-dried. The obtained lignin samples were analysed for purity using FT-IR (Fourier Transform Infrared Spectroscopy) and acid methanolysis-GC (Gas Chromatography) was used for determining the possible traces of carbohydrates in the extracted lignin samples. Chemical analysis was also done for the extracted wood materials. The extraction yield of lignin varied from 20% to 70% depending of the type of wood material. It was suggested that the degree of delignification was due to topochemistry of lignin and wood capillary structure. The different lignin samples contained only small amounts of residual carbohydrates and no traces of sodium xylenesulphonate were found after precipitating and washing. We also suggested that SXS was an attractive alternative as a green solvent for extraction of a lignin fraction that seemed to be pure enough to be further processed into new chemicals.