Influence of Fluorination on the Solubilities of Carbon Dioxide, Ethane, and Nitrogen in 1‑n‑Fluoro-alkyl-3-methylimidazolium Bis(n‑fluoroalkylsulfonyl)amide Ionic Liquids

International audienceThe effect on gas solubilities of adding partially fluorinated alkyl side chains either on imidazolium-based cations or on bis(perfluoroalkylsulfonyl)amide anions was studied. The aim was to gain knowledge of the mechanisms of dissolution of gases in fluorinated ionic liquids and, if possible, to improve physical absorption of carbon dioxide in ionic liquids. We have determined experimentally, in the temperature range of 298–343 K and at pressures close to atmospheric pressure, the solubility and thermodynamics of solvation of carbon dioxide, ethane, and nitrogen in the ionic liquids 1-octyl-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8mim][NTf2]), 1-octyl-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8mim][BETI]), 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[trifluoromethylsulfonyl]amide ([C8H4F13mim][NTf2]), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis[pentafluoroethylsulfonyl]amide ([C8H4F13mim][BETI]). Ionic liquids with partial fluorination on the cation were found to exhibit higher carbon dioxide and nitrogen mole fraction solubilities but lower ethane solubilities, compared to those of their hydrogenated counterparts. Molecular simulation provided insights about the mechanisms of solvation of the different gases in the ionic liquids

Absorption of carbon dioxide, nitrous oxide, ethane and nitrogen by 1-alkyl-3-methylimidazolium (C(n)mim, n = 2,4,6) tris(pentafluoroethyl)trifluorophosphate ionic liquids (eFAP).

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Influence of Fluorination on the Solubilities of Carbon Dioxide, Ethane, and Nitrogen in 1‑<i>n</i>‑Fluoro-alkyl-3-methylimidazolium Bis(<i>n</i>‑fluoroalkylsulfonyl)amide Ionic Liquids

The effect on gas solubilities of adding partially fluorinated alkyl side chains either on imidazolium-based cations or on bis­(perfluoroalkylsulfonyl)­amide anions was studied. The aim was to gain knowledge of the mechanisms of dissolution of gases in fluorinated ionic liquids and, if possible, to improve physical absorption of carbon dioxide in ionic liquids. We have determined experimentally, in the temperature range of 298–343 K and at pressures close to atmospheric pressure, the solubility and thermodynamics of solvation of carbon dioxide, ethane, and nitrogen in the ionic liquids 1-octyl-3-methylimidazolium bis­[trifluoromethylsulfonyl]­amide ([C₈mim]­[NTf₂]), 1-octyl-3-methylimidazolium bis­[pentafluoroethylsulfonyl]­amide ([C₈mim]­[BETI]), 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis­[trifluoromethylsulfonyl]­amide ([C₈H₄F₁₃mim]­[NTf₂]), and 1-(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)-3-methylimidazolium bis­[pentafluoroethylsulfonyl]­amide ([C₈H₄F₁₃mim]­[BETI]). Ionic liquids with partial fluorination on the cation were found to exhibit higher carbon dioxide and nitrogen mole fraction solubilities but lower ethane solubilities, compared to those of their hydrogenated counterparts. Molecular simulation provided insights about the mechanisms of solvation of the different gases in the ionic liquids

Transport properties and ionic association in pure imidazolium-based ionic liquids as a function of temperature.

International audienceIn this work, three transport properties (viscosity, diffusion coefficient, and electrical conductivity) were experimentally determined from 298 K to 343 K in four pure imidazolium-based ionic liquids with two anions and different alkyl chain lengths on the cation: 1-ethyl-3-methylimidazolium methylsulfate, [C1C2Im][CH3SO4], 1-butyl-3-methylimidazolium methylsulfate, [C1C4Im][CH3SO4], 1-ethyl-3-methylimidazolium triflate, [C1C2Im][CF3SO3] and 1-butyl-3-methylimidazolium triflate, [C1C4Im][CF3SO3]. Higher viscosities, lower diffusion coefficients, and electrical conductivities were measured when the alkyl chain length was increased or a sulfate anion was present. From these experimental data, the ionic association was discussed using the qualitative approach of the Walden plots and the quantitative ionicity concept. An increased ionic association was observed when the alkyl chain length on the cation was increased, while comparable ionicities were measured for both anions. Finally, the applicability of the Stokes–Einstein equation (relation between the diffusion coefficient and the viscosity) was also discussed in these systems

High-Pressure Densities of 2,2,2-Trifluoroethanol + Ionic Liquid Mixtures Useful for Possible Applications in Absorption Cycles.

International audience2,2,2-Trifluoroethanol (TFE) + ionic liquids constitute new possible refrigerant/absorbent pairs in refrigeration and heat absorption systems. In this work, volumetric data were measured on these systems in order to estimate their potential as alternatives to the commonly used fluids. Original high-pressure (up to 40 MPa) density data of mixtures 2,2,2-trifluoroethanol (TFE) + 1-methyl-3-ethylimidazolium tetrafluoroborate, [EMIm][BF4], or 1-methyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide, [BMIm][NTf2], have been measured in the temperature ranges 293.15–333.15 K and 283.15–333.15 K, respectively. Mixtures with [BMIm][NTf2] present higher densities and thus are more adequate for refrigeration systems. Excess molar volumes, VmE, and derived properties (isothermal compressibility, κT, and thermal expansion, αp) were calculated from experimental density data fitted to the Tait equation. αp and κT of the pure ionic liquids are smaller than those of the pure alcohol. Mixtures present derived properties similar to those of pure ionic liquids even at equimolar composition. From a technological aspect, these properties, being equivalent for both ionic liquids and most of their mixtures with TFE, will not be a criterion to select an absorbent–refrigerant pair. The excess molar volumes of the considered mixtures are small in absolute value and so can be considered as negligible when designing an absorption cycle. Finally, the PC-SAFT model was used to calculate the compressed densities. Acceptable results were obtained with trends as a function of temperature and pressure corresponding to what was experimentally observed. Using this model and a limited number of experimental data, the vapor pressures of the mixtures could be estimated with a reasonable precision