Characterization of Six Hygroscopic Ionic Liquids with Regard to Their Suitability for Gas Dehydration: Density, Viscosity, Thermal and Oxidative Stability, Vapor Pressure, Diffusion Coefficient, and Activity Coefficient of Water

Six hygroscopic ionic liquids (ILs), [DMIM]­[DMPO4], [EMIM]­[MeSO3], [EMIM]­[EtSO4], [EMIM]­[Et­(EG)2SO4], [BMIM]­[BF4], and [choline]­[glycolate], were investigated with regard to their suitability as a drying agent for technical gas dehydration processes by absorption. Therefore, the density, viscosity, activity coefficient of water in the ILs, and the kinetic parameters of thermal and oxidative degradation were measured (if the respective values were not already reported in the literature). [EMIM]­[MeSO3] proved to be the most suitable candidate for industrial gas dehydration. This IL has a low activity coefficient, a high thermal and oxidation stability, an acceptably low viscosity as well as a very low vapor pressure. Thus, the influence of temperature on the activity coefficient of water and the diffusivity of water in this IL was also determined.