Effect of Recycled Imidazolium-based Ionic Liquids on Biomass from Rubber Wood

Abstract

Background: Ionic liquids could be used as a potential solvent to dissolve rubber wood. This is one the most successful methods for the dissolution of rubber wood. Methods: In this study, various imidazolium-based ionic liquids with different anions, e.g acetate, chloride, dycanimide and ethylphosphonate were used to dissolve rubber wood and showed that 1-ethyl-3- methyl imidazolium acetate ([Emim][OAc]) could be recycled four times. There was a small decrease in the cellulose and lignin mass regenerated of the rubber wood using recycled ionic liquids compared to fresh ionic liquids. This method had achieved a recovery ionic liquid efficiency of 90% and the Fourier Transform Infrared (FTIR) and X-Ray Diffraction (XRD) showed that the crystallinity of the cellulose through the recycled ionic liquid has significantly decreased. The yield of the conversion of cellulose to glucose increased as the number of ionic liquid cycles increased, especially at the fourth instance of recycling. On the other hand, Thermogravimetric Analysis (TGA) and 1H NMR (nuclear magnetic resonance) spectroscopy showed no structural changes in the recovered ionic liquids. Conclusion: This work proves that [Emim][OAc] has an excellent reusability. Keywords: Ionic liquids, dissolution, rubber wood, recycle, pre-treatment, anions.