Identification and Evaluation of characteristics of Fractions of Industrial Softwood Kraft Lignin Separated by Single Step Fractionation

The inherent heterogeneity features of lignin when increased during kraft pulp process, restricts the technical lignin utilization in value added applications. Organic solvent fractionation of lignin is notable as an efficient way to obtain lignin fractions with well-defined characteristics. In the present study, two industrial kraft lignin were separated to the soluble and insoluble fractions by single step extraction process using acetone as organic solvent. The parent kraft lignin and the soluble and insoluble fractions thereof, characterized by using various techniques including GPC, FT-IR, 31P NMR and DSC.The results showed different molecular weight, functional hydroxyl groups and also glass Transition Temperature (Tg) for lignin fractions. The soluble fractions exhibited lower molecular weight and polydispersity, less aliphatic and more total phenolic hydroxyl groups and lower Tg than the soluble fractions. The results indicated that solvent assisted single step extraction can easily provide access to the industrial lignin fractions with different properties. Understanding correlations between physical-chemical properties of lignin fractions can be used as a tool for selection of tailored lignin fractions for the potential of value added applications.