Comparison of Structural Modification of Sugarcane Bagasse Cellulose Regenerated from Three Imidazolium-Based Ionic Liquids

Sugarcane bagasse cellulose (SBC) was dissolved in three imidazolium-based ionic liquids (ILs) [Emim]DEP, [Emim]Ac and [Bmim]Cl at the same conditions (1% mass loading, 110.). Among the three ILs, [Emim]DEP has the highest dissolution rate and regeneration yield of SBC. Both the original and regenerated SBC samples were characterized by X-ray diffraction, infrared spectroscopy, scanning electron microscopy and thermogravimetric analysis. The results showed that the crystal structure of SBC was rearranged from cellulose I to cellulose II after regeneration from all the three ILs, but different IL leads to a different degree of crystallinity index (CrI) reduction. The CrI of SBC regenerated from [Bmim]Cl was significantly decreased from 73.35% to 25.08%, which is the lowest in all samples. Surprisingly, the CrI value of regenerated SBC from [Emim]DEP was just a little higher than that of [Bmim]Cl, although the dissolution time of [Emim]DEP is much shorter than that of [Bmim]Cl. It was also found that the regenerated SBC from [Emim]DEP had better thermal stability when compared with the untreated and regenerated SBC from the other two ILs.