Ionic liquids: Efficient solvent and medium for the transformation of renewable lignocellulose

Carbon-enriched lignocelluloses are regarded as the perfect alternative for nonrenewable fossil fuel, and have a great potential to alleviate the increasing energy crisis and climate change. However, the tightly covalent structure and strong intra and inter-molecular hydrogen bonding in lignocellulose make it high recalcitrance to transformation due to the poor solubility in water or common organic solvents. Dissolution and transformation of lignocellulose and its constituents in ionic liquids have therefore attracted much attention recently due to the tunable physical-chemical properties. Here, ionic liquids with excellent dissolving capability for biomass and its ingredients were examined. The technologies for lignocellulose biorefining in the presence of ionic liquid solvents or catalysts were also summarized. Some pertinent suggestions for the future catalytic conversion and unitization of this sustained carbon-rich resource are proposed.