Fractionation And Characterization Of Kraft Lignin By Sequential Precipitation With Various Organic Solvents

Because of the heterogeneous feature, the high structural diversity and molecular weight distribution, the high value-added utilization of technical lignin is a difficult task. In the present study, a novel lignin fractionation method was successfully established by using low-priced organic solvents. The kraft lignin was fractionated into four fractions according to the molecular weight, namely the INS, SOL-I, SOL-II and SOL-III factions. The lignin samples were characterized by GPC, UV, elemental analysis, TGA, DSC and NMR. The results demonstrated that the kraft lignin was fractionated and purified to a certain extent, fractionated lignin was homogeneous with low polydispersity. There was no chemical reaction occurred during the fractionation process. The properties were in related with molecular weight. The decomposition temperature and glass transition temperature exhibited a decreasing trend with the decreasing of molecular weight.