Vapor–liquid equilibria (VLE), heat capacities, densities, and viscosities of mixtures of water and 1-ethyl-3-methylimidazolium acetate ([EMIM]­[OAc]) and mixtures of water and diethylmethylammonium methane sulfonate ([DEMA]­[OMs]) were measured in the temperature range T = (293.15 to 353.15) K. VLE measurements were carried out by Fourier transform infrared (FTIR) spectroscopy in a dynamic cell, and the experimental VLE data were correlated to the nonrandom two-liquid (NRTL) model. Measurements of the heat capacity were conducted via differential scanning calorimetry (DSC). The density was measured with a pycnometer and the viscosity with a falling-sphere viscometer.

New working pairs of room-temperature ionic liquids (RTILs) and water offer an opportunity to replace the highly corrosive and partly immiscible working pair of lithium bromide (LiBr) and water in absorption cycles like the absorption chiller. To estimate the suitability of these working pairs, the knowledge of thermophysical properties is inevitable. Due to the lack of literature data the following properties of two RTIL−water mixtures will be presented in this paper. Vapor−liquid equilibria (VLE) of the binary mixture of water + diethylmethylammonium trifluoromethanesulfonate ([DEMA][OTf]) and the ternary mixture of water + [DEMA][OTf] + diethylmethylammonium methanesulfonate ([DEMA][OMs]) were measured in the temperature range T = (293.15 to 353.15) K. The VLE measurements were carried out by Fourier transform infrared (FTIR) spectroscopy in a dynamic cell. The experimental VLE data were fitted with the nonrandom two-liquid (NRTL) model. Heat capacities, densities, and viscosities of the binary mixtures water + [DEMA][OTf] and [DEMA][OTf] + [DEMA][OMs] were measured. The measurements of the heat capacity were conducted via differential scanning calorimetry (DSC) in the temperature range T = (293.15 to 363.15) K. The density was measured with a pycnometer and the viscosity with a falling sphere viscometer. The temperature range for both was T = (293.15 to 353.15) K. Diffusion coefficients of water in the RTILs were determined by pulsed field gradient-nuclear magnetic resonance spectroscopy (PFG-NMR) in the temperature range of T = (288 to 313) K. ■ INTRODUCTIONRoom-temperature ionic liquids (RTILs) are salts which are liquid at room temperature and atmospheric pressure. They are composed of an organic cation and an inorganic or organic anion. Due to the numerous possible combinations of anions and cations, physical and chemical properties can be adapted over a wide range. 1,2 The most preferable properties for industrial applications are a low melting point, a wide liquid range, a negligible vapor pressure, and nonflammability. 3 This leads to a large number of possible applications in synthetic, analytical, and engineering processes. Today RTILs are used for example as extraction agents in separation processes, and they are also suited to replace conventional organic solvents due to their negligible vapor pressure. 3,4 Other fields of application such as the use as lubricants, in electrochemistry, and in bioscience are also being considered. 5,6 This led to an enormous increase of scientific investigations over the past years. 1−18 Our group is investigating new working pairs for the absorption chiller to replace the highly corrosive and partly immiscible but still commonly used working pair LiBr and water. 7,8 The absorption chiller offers the opportunity for ambient cooling by the usage of waste heat or solar energy. A description of the process can be found in literature. 9 The temperature range of the solution cycle in the process is set by the cooling water temperature in the absorber (around 298 K) and...