Effect of Pretreatment and Heating with Microwave on the Yield of Levoglucosan from Cellulose Treated with an Ionic Liquid, 1-Ethylpyridinium Bromide

Abstract

Recently, much attention has been paid to ionic liquid as solvents for woody biomass. Previously we reported that cellulose is partially dissolved and depolymerized into various low molecular weight compounds such as cellobiose, cellobiosan, glucose, levoglucosan, fructose and 5-hydroxymethylfurfural (5-HMF) in 1-ethylpyridinium bromide ([EtPy][Br]) at 120 ºC. Among these compounds, levoglucosan can be produced with high yield. In this study, therefore, we investigated the methods to enhance the yield of levoglucosan from cellulose as treated with [EtPy][Br] at 120 ºC. Pretreatment was studied to make cellulose amorphous by some ionic liquids, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) and 1-ethylpyridinium chloride([EtPy][Cl]). As the result, the yields of levoglucosan from cellulose were improved greatly by the pretreatment with all ionic liquids used. As another trial, we investigated the heating with microwave for [EtPy][Br] treatment. The yields of levoglucosan were higher in a shorter reaction time by microwave heating than by ordinal oil bath heating. These two methods were efficient to attain higher yield of levoglucosan from cellulose by treatment with [EtPy][Br].