Coordinating ionic liquids - efficient and greener solvents for dissolution and processing of biomass

The ability of ILs to directly dissolve biological macromolecules, such as cellulose, lignin, hemicellulose, chitin, silk fibroin, wool keratin, etc., has generated intense worldwide academic and industrial interest in a relatively short period of time. Selective to complete dissolution of these biological macromolecules using ILs can now be carried out under unmatched mild conditions, without evaporation of solvent molecules, and the ILs can be easily recycled and reused. Moreover, in general there is no significant decrease in the molecular mass of the regenerated macromolecules and chemical modifications of the dissolved macromolecules can easily be conducted with ILs suitable to the reaction conditions. All these advantages make the dissolution of macromolecules with ILs a desirable and promising process (H.Wang et al. 2014).

Advantages of ionic liquids as solvents

• Greener alternatives to volatile, environmentally undesirable organic solvents
• Uncomplicated and safe handling compared to conventional solvents
• Dissolve a wide range of biopolymers
• Excellent chemical & thermal stability & non-flammability
• Can easily be recycled and reused
• Selective to complete dissolution of biological macromolecules under mild conditions
• Chemical modification of macromolecules can easily be conducted in suitable IL solution

The first application of ILs in processing biomass was the dissolution of pure cellulose using imidazolium ILs. Since then, studies on the application of ILs in biomass chemistry have made great progress and now many ILs have been found to be able to dissolve biopolymers. A given type of IL might dissolve quite different biopolymers (H.Wang et al.2014).