Saccharification of cellulose in the ionic liquids and glucose recovery

High-efficiency hydrolysis of lignocellulose is critical for the production of second-generation bioethanol. In the present work, the acid hydrolysis of cellulose in ionic liquids (ILs) 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), 1-allyl-3-methylimidazolium chloride ([Amim]Cl), and 1-ethyl-3-methylimidazolium chloride ([Emim]Cl), respectively, was investigated and aqueous two-phase systems were constructed by adding salt solutions to ILs to recover glucose from cellulose hydrolyzates in the ILs. The effects of reaction temperature, reaction time and acid consumption on the cellulose hydrolysis efficiencies in the ILs were determined. The optimal cellulose hydrolysis conditions in ILs were found to be [Bmim]Cl, a reaction time of 0.5 h, an acid consumption of 0.25 mL/g (cellulose) and a reaction temperature of 100 °C. The yield of glucose under the optimal hydrolysis conditions reached 92.88%. IL-based aqueous two-phase systems were formed by adding NaOH, K3PO4, or K2HPO4 into the ILs containing glucose or cellulose hydrolyzates, which were able to partition the glucose into the bottom salt-rich phase. Under the optimum condition, 4 vol 50% NaOH or K3PO4 solution was able to partition 90% glucose, resulting in 16 g/L glucose in the salt-rich phase that could be further used for ethanol fermentation.