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Abstract: The densities, viscosities, and electrical conductivities of N-(2-hydroxyethyl) pyridinium bis(trifluoromethanesulfonyl)amide ([Py2OH][Tf2N]) have been measured over the temperature range T =273.15–363.15K at atmospheric pressure. The pressure–volume–temperature–composition relations in the CO2 +[Py2OH][Tf2N] system have been obtained under the pressure condition up to 5MPa at T =298.15, 313.15, and 333.15K. The densities and transport properties were well reproduced with a second order polynomial and Vogel–Fulcher–Tamman equations, respectively. The Walden plot (double logarithm graph of molar conductivity vs reciprocal viscosity) gives the straight line. [Py2OH][Tf2N] has higher densities and poor transport properties compared to an analog without the hydroxyl group, N-butylpyridinium bis(trifluoromethanesulfonyl)amide. The CO2 solubilities in [Py2OH][Tf2N] show typical pressure dependencies in both mole fraction and molarity scales as a physical absorbent. The molar volume in the liquid [Py2OH][Tf2N] phase decreases by the dissolution of CO2. The volume of ionic liquid phase expands with an increase of CO2. As a result, the saturated liquid density slightly decreases over the present 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]