Fractionation of corn stover into cellulose, hemicellulose and lignin using a series of ionic liquids

Lignocellulosic biomass is increasingly being promoted as an environmentally and economically sustainable fuel. However, the complex structure of lignocellulose makes it difficult to be fractionated, which limits its conversion into valuable products. In this work, a series of functional acidic ionic liquids (ILs) with a simple synthetic procedure were prepared. Fractionation of corn stover into cellulose, hemicellulose and lignin was successfully performed in ultrasound-assisted ILs at a low reaction temperature of 70 °C for 3 h followed by alkaline extraction. IL-isolated lignin, alkaline lignin, hemicellulose and cellulose were obtained in good yields and their chemical properties were analyzed by FTIR. Significantly, a good yield of IL-isolated lignin was obtained, which accounted for 60.48% of the original lignin. The IL-isolated lignin was S-G-H type indicating by 13C NMR and 13C–1H correlation 2D NMR (HSQC) analysis. Enzymatic hydrolysis of cellulose was performed successfully. A high yield of 97.77% reducing sugar was achieved. Glucose and cellobiose were measured by HPLC analysis, which accounted for 92.55% of cellulose conversion. Both of the hydrogen bond capability and the acidity of ILs contributed to achieve the effective fractionation. These ILs have a great potential for the preparation of biofuel.