(276b) Investigation of Lignin Streams Generated during Ionic Liquid Pretreatment of Lignocellulosic Biomass

Lignin is a complex three-dimensional amorphous polymer derived from paracoumaryl, coniferyl, and synapyl alcohols, cross-linked together by different a number of linkages. In plant cell walls, lignin fills the spaces between cellulose and hemicellulose, and it acts like a â??glueâ?? that holds the lignocellulose matrix together. Despite years of research, the lignin structure is still not well understood as a function of feedstock and process. The ability of certain ionic liquids (ILs) to dissolve cellulose and/or lignin enables the possibility of commercial lignin upgrading and valorization to improve the overall biorefinery economics. However, to date depolymerization mechanisms of lignin in ILs is not well understood. In this study, the changes in the chemical composition of lignin after pretreatment with IL were investigated. Three different type of biomass, namely switch grass, eucalyptus and pine were utilized in this study. The relative changes in the common β-O-4, β-β and β-5 inter-unit linkages of lignin during pretreatment process were investigated using solution state two dimensional (2D) nuclear magnetic resonance (NMR). The changes in the size and molecular weight distribution of lignin were analyzed using size exclusion chromatography (SEC) and mass spectrometry.