Separation of Cellulosic Biomass from Ionic Liquids using Compressed CO2

The rigid hydrogen bonding network between cellulose molecules renders it insoluble in most organic solvents.  However, select ionic liquids (ILs) including 1-ethyl-3-methylimidazolium diethyl phosphate [EMIm][DEP] are capable of dissolving significant quantities.  Through IL pretreatment cellulose crystallinity is reduced thus enhancing reactivity.  As pre-processed cellulose is non-volatile, anti-solvent techniques are most often used for the separation from ionic liquids.  We have recently discovered that compressed carbon dioxide presents a unique alternative to conventional organic/aqueous antisolvent methods.  Phase equilibrium, high pressure NMR, and solid state NMR results will demonstrate characteristics of the CO₂ based physical (non-reactive) separation process and the amorphous cellulose product.