CO2 fluidisation of xylitol based deep eutectic solvents

Deep eutectic solvents (DES) are mixtures of two or more small molecules where strong intermolecular interactions lead to the formation of liquids at room temperatures. These solvents have wide applications from biomass extraction to syntheses, potentially replacing toxic and volatile organic solvents with liquids that can be made from more environmentally friendly components. We have been focusing on using DES to extract and functionalise lignin from waste biomass. However many of these DES are highly viscous and diffusion within the solution affects the uniformity of heating, the swelling of biomass by solvent and also the movement of lignin species out of the biomass into the solvent. To lower the viscosity various small molecule species can be added to a DES, most commonly water. Yet water is an anti-solvent for lignin. Instead we are fluidising our DES using CO2 and investigating the fluidised DES as novel solvents in biomass extraction. Here we wish to understand how CO2 is solubilised in a deep eutectic solvent based on xylitol:oxalic acid: ethylene glycol and how this affects its interaction with a model species mimicking lignin to better understand how this solvent solubilizes lignin and the effects of CO2 fluidisation of the solvent on the extraction process.