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Abstract: We have focused on a protic ionic liquid, ethylimidazolium bis(trifluoromethanesulfonyl)amide ([eimH][Tf2N]), and the analogous aprotic ionic liquid, 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([emim][Tf2N]). Densities, viscosities, and electrical conductivities of the two ionic liquids have been measured over the temperature range T =(273.15–363.15)K at atmospheric pressure. The densities of [eimH][Tf2N] and [emim][Tf2N] decrease with increasing temperature. The protic ionic liquid has the higher density (the smaller molar volume) than the aprotic one. The transport properties of the two ionic liquids show ordinary temperature dependencies. [eimH][Tf2N] has the higher viscosities (smaller electrical conductivities) than [emim][Tf2N]. Empirical Walden products indicate that [eimH][Tf2N] shows smaller conductivities than [emim][Tf2N] at certain viscosities. To investigate CO2 absorption properties of the ionic liquids, binary phase equilibria in CO2 +ionic liquid systems have been investigated under high pressures up to 6MPa at T =(298.15, 313.15, 333.15)K. The solubilities of CO2 in [eimH][Tf2N] and [emim][Tf2N] show typical pressure dependencies in both mole fraction and molarity scales as physical absorbents. The mole fraction of CO2 in [eimH][Tf2N] is slightly smaller than that in [emim][Tf2N] under the conditions investigated, while the molarity of CO2 in [eimH][Tf2N] is comparable to that in [emim][Tf2N]. The molar volumes in ionic liquid phase almost linearly decrease with the mole fraction of CO2 in the present systems. The partial molar volume of CO2 in [eimH][Tf2N] at infinite dilution is almost same as that in [emim][Tf2N]. [Copyright &y& Elsevier]

Abstract: The pressure–volume–temperature–composition relations for CO2 +pyrrolidinium-based ionic liquid systems were measured over the pressure range up to 6MPa at T =(298.15, 313.15, 333.15)K. Three ionic liquids were studied in the present work: N-methyl-N-propylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([Pyr13][TFSA]), N-methoxymethyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)amide ([Pyr1,1O1][TFSA]), and N-methoxymethyl-N-methylpyrrolidinium bis(fluorosulfonyl)amide ([Pyr1,1O1][FSA]). The pressure dependence of CO2 solubility indicates that CO2 molecules are dissolved physically in the three ionic liquids. The mole fraction scaled solubility of CO2 in [Pyr1,1O1][TFSA] is almost the same as that in [Pyr13][TFSA], and [Pyr1,1O1][FSA] showed the smallest solubility at certain pressures and temperatures. On the other hand, the molarity scaled solubility of CO2 in [Pyr1,1O1][TFSA] was nearly equal to that in [Pyr1,1O1][FSA]. The CO2 solubility of [Pyr13][TFSA] was smaller than the other two ionic liquids. The molar volume and density of ionic liquid phase decrease monotonically with an increase of mole fraction of CO2. The volume expansion of liquid phase was not almost dependent of temperature but composition of CO2 under the conditions investigated. [Copyright &y& Elsevier]

Abstract: We have determined the electrical conductivity in CO2-saturated 1-butyl-3-methylimidazolium hexafluorophosphate ([C4mim][PF6]) at 298.1, 313.1 and 333.1K as a function of CO2 pressure. Moreover, self-diffusion coefficients of cation and anion in CO2-saturated [C4mim][PF6] have been measured at high pressures up to ∼15MPa and at a fixed temperature of 333.2K by 1H and 19F NMR using the pulsed field gradient spin-echo method. As CO2 dissolves in [C4mim][PF6], marked increases in all the three transport quantities were observed at lower pressure, and then they showed very slight changes at higher pressure. The correlation between the conductivity and the ionic diffusion coefficients has been discussed. [Copyright &y& Elsevier]