Carbohydrates-based deep eutectic solvents: Thermophysical properties and rice straw dissolution

Deep Eutectic Solvents (DESs) have recently emerged as green alternatives to ionic liquids (ILs). Encouraged by the sustainability of this novel class of solvents, the aim of this work is to prepare DESs using three different hydrogen bond acceptors (HBA), such as cholinium chloride, acetylcholinium chloride and benzyldimethyl(2-hydroxyethyl)ammonium chloride and five naturally occurring carbohydrates, namely D-(+)-Xylose, D-(+)-Mannose, D-(−)-Fructose, D-(+)-Glucose and D-(−)-Ribose, which will act as hydrogen bond donors (HBD). NMR and FTIR were used to ascertain about the chemical structures and purities of these carbohydrates-based DESs, while their thermal properties were evaluated through DSC and TGA analysis. Due to the high viscosity of the carbohydrate-based DESs, and its high hydrophilic and hygroscopic nature, 10 wt% of water was added to mimic its use under normal atmosphere conditions and enable their use as solvents. Densities and viscosities at atmospheric pressure and in the temperature range between 293.15 K and 353.15 K were measured for the prepared DES aqueous solutions. Finally, the suitability of these carbohydrates-based DESs as solvents for the dissolution of rice straw was investigated.