Decomposition of cellulose in an ionic liquid, 1-ethyl-3-methylimidazolium chloride

Abstract

We investigated the decomposition of cellulose upon heating in an ionic liquid, 1-ethyl-3-methylimidazolium chloride ([C2mim][Cl]), in air and we studied the reactions of various cellulose decomposition compounds such as cellobiose, cellobiosan, glucose and levoglucosan. We propose two possible decomposition pathways for cellulose during [C2mim][Cl] treatment in air. One pathway is the hydrolysis of cellulose to cellobiose and glucose because [C2mim][Cl] can retain water even at higher than 100 °C, the boiling point of water. The other pathway is the depolymerization of cellulose to cellobiosan by a reaction of the hydroxy group at the C6 position in the glucose residue to form a glycosidic bond. The obtained cellobiosan is then depolymerized to two molecules of levoglucosan by a similar reaction of the hydroxy group at the C6 position. The levoglucosan produced is further hydrolyzed to glucose. Therefore, several products from cellulose decomposition are converted to glucose, which is the final hydrolyzed product. Furthermore, the obtained glucose can be further dehydrated to 5-HMF.