Energy-Saving Biomass Processing with Polar Ionic Liquids

Ionic liquids (ILs), which are organic salts with melting points of lower than 100°C, have been prepared as potential solvents for extracting cellulose. The hydrogen-bonding basicity ( β value) of ILs is an important parameter for evaluating their capability to dissolve cellulose. Some polar ILs with large β values have been synthesized based on the relationship between ion structure and the β value of the corresponding ILs. Some other ILs containing carboxylate anions or phosphonate derivatives have been confirmed to dissolve cellulose under mild conditions. Bran, a typical biomass, was mixed with polar ILs to extract cellulose. The solid crosslinked lignin was filtered out, and the filtrate was mixed with excess methanol to precipitate cellulose and hemicellulose. Because both ILs and methanol can be used repeatedly, this process can be operated in a closed system to separate lignin and polysaccharides (mainly cellulose).