Hydrolysis of cellulose to produce glucose with solid acid catalysts in 1-butyl-3-methyl-imidazolium chloride ([bmIm][Cl]) with sequential water addition

Selective glucose production by cellulose hydrolysis with initial or sequential water addition in the presence of solid acid catalysts in 1-butyl-3-methyl-imidazolium chloride ([bmIm][Cl]) under microwave irradiation was investigated at 120 °C and 1.2 MPa of N₂ atmosphere. For revealing the effect of water on cellulose hydrolysis in [bmIm][Cl], the phase behavior during the reaction was observed. Colored compounds formed at lower amounts of water, while some amounts of cellulose precipitated at higher amounts of water. Glucose yield was highest (65 mol%) at 25 wt% water in [bmIm][Cl] for the case of initial water addition. To improve the glucose yield, sequential water addition in which water was added in steps as the reaction proceeded was examined. Glucose yields in the presence of Amberlyst-15 in [bmIm][Cl] were 68.5 and 75.0 mol% by two-step and three-step water addition, respectively. Employing three-step water addition, Dowex 50wx8-100 (ion-exchange resin), hydrothermally synthesized carbon catalyst and three types of nano-zeolites were assessed. The carbon catalyst-modified fuming sulfuric acid and H-type zeolites (mordenite and faujasite) gave comparable glucose yields as Amberlyst-15. Sequential water addition is an effective technique for improving reaction efficiency in cellulose/solid acid catalyst/ionic liquid reaction systems.