(279c) Theoretical and Experimental Studies of Water Absorption Into Ionic Liquids

Thermodynamic and transport properties of water absorption in ionic liquids (ILs) are studied from both classical and ab initio simulation methods and experiments.  Ab initio gas phase calculations show that anions are categorized into three groups in terms of interaction with water, i.e., the weak (< 45 kJ/mol) , intermediate (50-65 kJ/mol) and strong types (70-85 kJ/mol), which correspond to hydrophobic ILs and ILs with high and very high water solubilities, respectively. Replacing the -CH3 (electron dinating) with the -CF3 (elelectron withdrawing) group in the anion colud decrease water-anion interactions about 11-17 kJ/mol for two different types of anions. The electrostatic interactions between water and ions are significantly stronger than van der Waals interaction. Cation effects on water solubility will also be discussed. Both simulations and experimental data show that the dynamics for the IL studied is significantly improved at high water concentrations. Very imteresting, at about 40-50% water concentrations, the stuided IL and water exhibit a local minimum of self-diffusivity both from simulations and experiments. The self-diffusivity for H2, N2, O2, CO2, CH4, and H2O in two different ILs will also be compared.