Dissolution of Cellulose in Ionic Liquids Assisted with Ethanol Pretreatment

One of the major current challenges to the chemical industry is the efficient use of renewable lignocellulosic biomass for the production of performance materials, platform chemicals, and biofuels. Dissolution of natural polymers including cellulose in ionic liquids has attracted much more attention around all over the world. However, the time for complete dissolution of cellulose in ionic liquids was too long for processing and derivatization to produce industrial materials. Herein, ethanol pretreatment was introduced to improve cellulose dissolution in ionic liquids. The pretreated cellulose was easily wetted and penetrated for dissolution in ionic liquids, which efficiently avoided the formation of the agglomerates of cellulose mixed with air wrapped with viscous ionic liquids. The dissolution time of pretreated cellulose could decrease to 75 min under the given conditions. FT-IR and CP/MAS 13C-NMR analyses indicated that ethanol pretreatment and dissolution in ionic liquid did not lead to any functionalization of cellulose. It was also found that the crystalline structure of native cellulose was destroyed and the regenerated cellulose was mainly composed of amorphous structure. The thermal stability of cellulose decreased and the pyrolysis residues increased after dissolution and regeneration.