CO2 solubility and physical properties of N-(2-hydroxyethyl)pyridinium bis(trifluoromethanesulfonyl)amide

The densities, viscosities, and electrical conductivities of N-(2-hydroxyethyl) pyridinium bis(trifluoromethanesulfonyl)amide ([Py2OH][Tf2N]) have been measured over the temperature range T = 273.15–363.15 K at atmospheric pressure. The pressure–volume–temperature–composition relations in the CO2 + [Py2OH][Tf2N] system have been obtained under the pressure condition up to 5 MPa at T = 298.15, 313.15, and 333.15 K. 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.