Thermal Conductivities of [bmim][PF6], [hmim][PF6], and [omim][PF6] from 294 to 335 K at Pressures up to 20 MPa

Abstract

Thermal conductivities are reported for a series of 1-alkyl-3-methylimidazolium hexafluorophosphates having butyl, hexyl, and octyl groups, which are expressed by [bmim][PF 6 ], [hmim][PF 6 ], and [omim] [PF 6 ], respectively. The experimental method used was a transient short-hot-wire method. Since only a small amount of sample liquid is required, this method was found to be effective for the thermal-conductivity measurements of ionic liquids (ILs). The experimental temperatures ranged from 294 to 335 K at pressures up to 20 MPa. The values of the thermal conductivities of ILs at normal pressure are similar to those of benzene. It was found that an effect of the length of the alkyl chain on the thermal conductivities in ILs is negligible. From the data for the thermal conductivity and viscosity at 293.15 K and 0.1 MPa of ILs and normal alkanes, a simple correlation was developed based on the Mohanty theory. From comparisons between the thermal conductivities of ILs and those of organic liquids (n-hexane, benzene, and methanol), the temperature and pressure dependences of the thermal conductivity of ILs are relatively weak.

Thermal Conductivities of Imidazolium-Based Ionic Liquid + CO2 Mixtures

“…[2] Since ILs are highly electrically conducting liquids, one should consider the effect of current leakage. As described in our previous article [3], the effect of leakage current was negligible at these experimental conditions.…”

“…The liquid samples of 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim] [PF 6 ]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]) were prepared following procedures reported previously [2,3]. The product purity was confirmed by CHN elementary analysis.…”

“…The thermal conductivities of the mixtures were measured with the transient shorthot-wire method, which has been described in detail elsewhere [2,3]. The transient short-hot-wire cell used in this study is shown in Fig.…”

“…Platinum lead wires for electric current heating and voltage measurement were welded to a platinum lead terminal. The maximum volume of the stainless-steel pressure-resistant cell was approximately 65 cm 3 . In this cell, the pressure was regulated by moving a piston at the lower end of the short-hot-wire cell using a pressure medium.…”

“…Thermal conductivity is one of the most important physical properties to design chemical processes. Thermal conductivities of ILs were measured by several researchers [1][2][3][4]. However, there are no literature data for IL + CO 2 mixtures.…”