Thermal conductivity of the ionic liquid [HMIm][Tf₂N] with compressed carbon dioxide

Abstract

The liquid thermal conductivity of the ionic liquid (IL), 1‐hexyl‐3‐methyl‐imidazolium bis(trifluoromethylsulfonyl)amide ([HMIm][Tf2N]), saturated with compressed vapor and supercritical carbon dioxide was measured over three isotherms (298.15, 323.15, and 348.15 K) and pressures up to approximately 20 MPa using a transient hot‐wire technique. Pure [HMIm][Tf2N] thermal conductivity was also measured over a temperature range of 293.15–353.15 K at ambient pressure and with hydrostatic pressure to approximately 20 MPa. Literature vapor–liquid equilibrium data were used to predict the liquid CO2 composition at the conditions investigated. Initially, the liquid thermal conductivity slightly decreased with pressure/composition of CO2 followed by a gradual increase that is mainly attributed to hydrostatic pressure effects. Simple composition‐based mixing rules for mixture properties are not qualitatively nor quantitatively accurate. These data could be used to engineer heat transfer equipment required for a variety of proposed IL applications in CO2 capture, absorption refrigeration, biphasic CO2/IL reaction platforms, etc.

Phase Equilibrium and Transport Properties of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)amide and Compressed Difluoromethane and Pentafluoroethane

“…A Flucon Fluid Control GmbH thermal conductivity probe employing the transient hot-wire technique is coupled with a high-pressure equilibrium cell to measure the thermal conductivity of the biphasic IL/refrigerant mixtures. A detailed description of the system and the derivation of the governing equation are provided in our previous work, , and an overview is provided here. A transient hot-wire sensor equipped with a platinum wire is used with a high-pressure equilibrium cell that is loaded with an initial amount of IL.…”

“…In our previous study, we have shown that the thermal conductivity of CO 2 -saturated [HMIm][Tf 2 N] increases in certain regions of solubility. 10 This phenomenon appears to be due to the increased pressures required to dissolve CO 2 in the IL to a certain composition. Hence, the hydrostatic pressure exerted may cause an increase in mixture thermal conductivity and we have shown for the pure IL thermal conductivity.…”

“…The molecular tunability and unique characteristics of ionic liquids (ILs) allow for their potential use in a wide array of engineering applications. Many of the proposed applications include biphasic systems of ILs coupled with gases, for instance, in absorption refrigeration, − CO 2 capture, − lubrication for gas compression, , and gas separations among many others. − Of particular interest to this study is the proposed application of ILs in the separation of hydrofluorocarbon (HFC) gas blends. HFCs are a subset of fluorinated gases (F-gases) commonly used in refrigeration, air-conditioning, heat pumps, fire extinguishing, foam blowing, etc .…”

Novel amino acid ionic liquids prepared via one‐step lactam hydrolysis for the highly efficient capture of CO2

“…[9][10][11] ILs have their own unique properties that favor for practical applications. 12,13 ILs usually have very low saturated vapor pressure, even under high vacuum conditions, so that environmental pollution caused by volatilization can be greatly avoided. 14,15 ILs have also good thermal and chemical stability, as well as outstanding capacity to dissolve organic and inorganic substances.…”

“…New methods have been developed to capture CO 2 efficiently using ILs through chemical interactions 9–11 . ILs have their own unique properties that favor for practical applications 12,13 . ILs usually have very low saturated vapor pressure, even under high vacuum conditions, so that environmental pollution caused by volatilization can be greatly avoided 14,15 .…”