Extraction of lignin and quantitative sugar release from biomass using efficient and cost-effective pyridinium protic ionic liquids

Abstract

Lignocellulosic biomass is enormously abundant around the globe. It bears huge potential for renewable products as its components can be converted to many useful products via cheaper processes. Recently, the component of biomass that has attracted enormous attention is lignin owing to its several aromatic or phenolic constituents. The utilization of lignin, however, is hindered by its troublesome separation mainly due to the difficult nature of the lignocellulosic biomass. Protic ionic liquids have great potential for extraction of lignin from the lignocellulosic biomass to make it viable for various transformations. In this study, protic ionic liquids comprising a pyridinium cation and a dihydrogen phosphate anion (H₂PO₄⁻) were prepared and used for lignin extraction and subsequent saccharification of the cellulose pulp. The ILs exhibited appreciably high lignin yields (optimum 73%) under mild conditions (100 °C) and shorter time (2 h). Fairly good sugar (glucose) yields (77%) verify effective delignification. The analysis of ILs and biomass was accomplished by H-NMR, FT-IR, SEM, HSQC and GPC.