Thermophysical Study of Pyridinium-Based Ionic Liquids Sharing Ions.

The thermophysical properties of three pyridinium-based ionic liquids sharing ions were measured at several temperatures (278.15-338.15) K and at atmospheric pressure (0.1 MPa). Three ionic liquids were studied: 1-butylpyridinium bis(trifluoromethyl-sulfonyl)imide, 1-hexylpyridinium bis(trifluoromethylsulfonyl)imide, and 1-hexylpyridinium tetrafluoroborate. The following thermophysical properties were measured: density, speed of sound, refractive index, surface tension, isobaric molar heat capacity, kinematic viscosity, and electrical conductivity. The thermophysical properties at atmospheric pressure were correlated with temperature, noting that the starting temperature for the speed of sound measurements depended on the ionic liquid. From these experimental results, some derived properties (isentropic compressibility, molar refraction, and dynamic viscosity) are calculated. These results together with those published previously for 1-butylpyridinium tetrafluoroborate are discussed.