Isobaric Thermal Expansivity for Ionic Liquids with a Common Cation as a Function of Temperature and Pressure

Abstract

Isobaric thermal expansivity α p as a function of temperature and pressure was determined by means of a calorimetric method for a set of ionic liquids with a common cation within the temperature and pressure intervals (278.15 to 348.15) K and (5 to 50) MPa. The selected common cation was 1-butyl-3-methylimidazolium, whereas the chosen anions were tetrafluoroborate, bis(trifluoromethylsulfonyl)imide, hexafluoroantimonate, trifluoromethanesulfonate, and methylsulfate. The results are compared with available literature data, obtained from density measurements. An unusual, negative dependence of α p against temperature was found for all liquids over the whole temperature and pressure interval. The results are discussed in terms of the differences in the chemical nature of the anions.

Thermophysical Properties of 1-Butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [C4mim][(C2F5)3PF3], and of Its IoNanofluid with Multi-Walled Carbon Nanotubes

“…As for isobaric expansivity, values were found to decrease with an increase in temperature. This anomalous behavior was reported in several other ionic liquids. − Values are like those of three more ILs based on the [FAP] − anion. , Expanded absolute uncertainties associated with the isobaric expansivity, thermal expansivity, and isothermal compressibility, at a 95% confidence level, were found to be U ( α P ) = (0.04 to 0.14) × 10 –4 K –1 , U ( κ S ) = 0.01 × 10 –10 Pa –1 , and U ( κ T ) = 0.02 × 10 –10 Pa –1 , respectively.…”

Anomalous and Not-So-Common Behavior in Common Ionic Liquids and Ionic Liquid-Containing Systems

“…Again, α p decreases as temperature increases in the low-T range (Figure 1B). Navia et al (2010a), Navia et al (2010b) also obtained data for a large set of ILs confirming negative (∂α p /∂T) p values at low temperatures.…”

“…The top four unlabeled isobars in the right panel correspond to pressures of 0.1, 0.25, 0.5, and 1 MPa. The red lines represent the boundaries of the data presented by Navia et al (2010a), Navia et al (2010b) (isotherms between 293 and 353 K and isobars between 5 and 50 MPa). The green lines highlight the same boundaries for the set of data measured by Nieto de Castro et al (2010).…”

CHAPTER 14. High-Pressure “Maxwell Relations” Measurements

“…45 This is confirmed by an observation that the isobaric heat capacity of ionic Figure 14.12 Isotherms of the coefficient of thermal expansion for selected ionic liquids. 43 liquids rises with pressure, similarly to the simple liquids at high pressures. 46 The reported parallelism of a isotherms is most probably only apparent because the temperature and pressure ranges investigated were rather narrow, 278.15-348.15 K and 5-50 MPa, respectively.…”

“…42 However, all the measurements have been performed over narrow pressure (5- Figure 14.12 presents thermal expansion isotherms for selected ionic liquids derived from fitting equations established on the basis of experimental data. 43,44 At first glance, two features are striking: a values decrease with temperature (da/dTo0) and the a isotherms are almost parallel. The first observation can be compared to the behaviour of a isotherms above the crossing point, observed for simple liquids, where the thermal expansion coefficient decreases with rising temperature.…”