Imidazolium-based ionic liquids for cellulose pretreatment: recent progresses and future perspectives

As the most abundant biomass in nature, cellulose is considered to be an excellent feedstock to produce renewable fuels and fine chemicals. Due to its hydrogen-bonded supramolecular structure, cellulose is hardly soluble in water and most conventional organic solvents, limiting its further applications. The emergence of ionic liquids (ILs) provides an environmentally friendly, biodegradable solvent system to dissolve cellulose. This review summarizes recent advances concerning imidazolium-based ILs for cellulose pretreatment. The structure of cations and anions which has an influence on the solubility is emphasized. Methods to assist cellulose pretreatment with ILs are discussed. The state of art of the recovery, regeneration, and reuse aspects of ILs is also presented in this work. The current challenges and development directions of cellulose dissolution in ILs are put forward. Although further studies are still much required, commercialization of IL-based processes has made great progress in recent years.