Recent trends in (ligno)cellulose dissolution using neoteric solvents: switchable, distillable and bio-based ionic liquids

Recent years have witnessed the use of different ionic liquids for biomass processing, either at the level of lignocellulose pre-treatment, to fractionate biomass in its main components, separating hemicellulose and lignin from cellulose, or directly in cellulose decrystallization by dissolving it in the ionic liquid and subsequent precipitation by adding anti-solvents. Yet, most of the ILs employed in these strategies (e.g. imidazolium-based solvents) are (still) expensive for such applications, and provide discussable ecological footprints. In an attempt to combine the highly useful generated knowledge with novel neoteric solvents with improved properties, economics, availability and ecology, several new trends have appeared in these areas during recent years. They comprise the use of switchable ILs, based on strong organic bases and CO2, the application of distillable ILs, as well as the use of bio-based and low-cost ILs and deep-eutectic-solvents (DES), e.g. choline chloride-based derivatives. Apart from other emerging uses, for all these solvents some preliminary applications in biomass processing involving pretreatments, cellulose dissolution and other applications have been successfully reported. This Minireview contextualizes these recent trends and discusses them with emphasis on future use of them in biorefineries and biomass valorization. (c) 2013 Society of Chemical Industry