Reaction behavior of cellulose in various pyridinium-based ionic liquids

Abstract

We investigated the reaction behavior of cellulose in the pyridinium-based ionic liquids 1-ethylpyridinium chloride ([EtPy][Cl]), 1-ethylpyridinium bromide ([EtPy][Br]), and 1-ethylpyridinium iodide ([EtPy][I]). The cellulose was treated with the ionic liquids at 120 °C, and was found to exhibit quite a different reaction behavior in each of the different ionic liquids. Cellulose is completely dissolved and depolymerized in [EtPy][Cl]. In contrast, [EtPy][Br] only partially reacts with cellulose, while [EtPy][I] does not dissolve and react with cellulose at all. At the beginning of the treatment, cellulose was depolymerized with [EtPy][Cl] and [EtPy][Br] into various low molecular weight compounds such as cellobiose, cellobiosan, glucose, levoglucosan, and 5-hydroxymethylfurfural. As the treatment continued, some of the low molecular weight compounds reacted to form polymers. These ionic liquids are therefore not only a solvent for cellulose, but also a reagent for both its depolymerization into various low molecular weight compounds and subsequent polymerization of those compounds.