Select ionic liquids (ILs) are capable of dissolving significant quantities of biomass (cellulose, hemicellulose, and lignin). Various processing schemes have been developed utilizing “anti-solvents” for separating all or certain fractions of biomass. While the vast majority of organic solvents and water act as anti-solvents for cellulosic biomass, certain polar aprotic solvents actually act more like cosolvents when mixed with ionic liquids. These cosolvents may be utilized to improve the thermodynamic and transport properties of the ionic liquid for biomass dissolution. In this presentation, the effect of cosolvents and antisolvents on the solid-liquid equilibrium in a model system of cellulose and the ionic liquid, 1-ethyl-3-methylimidazolium diethyl phosphate [EMIm][DEP] are investigated. Various cosolvents and antisolvents will be explored, including water, polar protic and aprotic solvents, and compressed CO<sub>2</sub>. Our findings indicate that some co-solvents may actually increase the solubility of cellulose in ionic liquid mixtures. Moreover, these mixtures have vastly lower viscosity and are more tolerant to water which is ubiquitous in biomass. Compressed CO<sub>2</sub> may represent an advantageous anti-solvent for precipitation as it may be less energy intensive than evaporation/distillation of an organic solvent or water. Spectroscopic techniques including NMR, IR, and Kamlet Taft parameter measurements from solvatochromic probes will help elucidate bulk and molecular interactions between the species.

Cosolvent and anti-solvent effects for cellulose processing in ionic liquids

251st National Meeting (2016)

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