Elsevier

Fluid Phase Equilibria

Volume 314, 25 January 2012, Pages 161-168
Fluid Phase Equilibria

Solubilities of several non-polar gases in mixtures water + 2,2,2-trifluoroethanol at 298.15 K and 101.33 kPa

https://doi.org/10.1016/j.fluid.2011.11.006Get rights and content

Abstract

Solubilities of nine nonpolar gases (H2, N2, O2, CH4, C2H6, C2H4, CF4, SF6, and CO2) in mixtures of water + 2,2,2-trifluoroethanol (TFE) at 298.15 K and 101.33 kPa partial pressure of gas are reported. A polynomial dependence of the solubilities on the mole fraction of the binary liquid mixture is found. The Henry's constants at the vapour pressure of water, the standard changes in the Gibbs energy for the solution process and for the solvation process, and the so-called excess Henry's constant are calculated. Gibbs energies for the solution process and excess Henry's constants have been calculated using the Scaled Particle Theory (SPT).

Highlights

► Solubility of H2, N2, O2, CH4, C2H4, C2H6, CF4, SF6 and CO2 in water + TFE at 298.15 K and 101.33 kPa was determined. ► Changes in the Gibbs energies of the solution and solvation processes were calculated. ► lnKH3,12E are negative except in the zone highly dilute in TFE (x2<0.04). ► Remarkable features arise from the behaviour of ΔG¯solv for CO2, CF4 and SF6. ► SPT provides acceptable results despite its simplicity.

Introduction

This work is a continuation of that presented in several earlier papers [1], [2], [3], [4] where the solubilities of non-polar gases in two fluorinated alkanols, namely, 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP), and their mixtures with water were reported. The interest of these mixtures fluoroalkanol–water lies in the possibility that they have of modulating properties that influence on the kinetics of Diels–Alder reactions [5] as well as in their effectiveness to stabilize the α-helical structure of peptides and proteins [6] which is important for the study of these biological compounds. In these phenomena the solvophobicity of the liquid solvent is very important and the solubilities of non-polar gases in liquids have shown their ability to provide information about it [7]. Gas solubilites can also be used at a fundamental level to estimate molecular properties such as the Lennard–Jones potential parameters [8].

Here the solubilities of nine non-polar gases (H2, N2, O2, CH4, C2H6, C2H4, CF4, SF6, and CO2) in mixtures of water with TFE at 298.15 K and 101.33 kPa partial pressure of gas are reported. The mixtures cover the composition range comprehended within 10 and 90 per cent in volume. The solubilities are expressed by the mole fraction of gas dissolved and also by the Henry's constant as a function of the liquid phase composition given by the mole fraction of TFE. These results complete the study of the solubilities of noble gases in the same mixture water + TFE [4] by considering several diatomic gases along with a set of polyatomic gases of different chemical nature (hydrocarbons, fluorinated gases, carbon dioxide).

From the solubility data, the change in the standard Gibbs energy for both solution and solvation processes has been calculated. The Gibbs energies for the solvation process provide useful information about the behaviour of the liquid solvent mixture in the water-rich zone. In addition, the Scaled Particle Theory (SPT) [8], [9], [10], [12] has been used to predict the solubilities with the aim of verifying the validity of the model in these ternary solutions.

Section snippets

Materials

The gases used were hydrogen, nitrogen, oxygen, methane, ethane, ethylene, sulfur hexafluoride and carbon dioxide, all supplied by Air Liquide España, along with carbon tetrafluoride supplied by J.T. Baker. For the liquids, 2,2,2-trifluoroethanol was provided by Fluorchem Ltd., and ultrapure water was obtained in our institution facilities using a Millipore device. All the chemicals were used without further purification and their description appears in Table 1.

Apparatus and procedure

The equipment employed for

Solubility and Gibbs energies for both solution and solvation processes

Solubility of the nonpolar gases H2, N2, O2, CH4, C2H6, C2H4, CF4, SF6, and CO2 in mixtures water + TFE at 298.15 K and 101.33 kPa partial pressure of gas, are reported in Table 3 for different mole fractions of TFE, x2, in the binary solvent mixture. Solubilities are expressed as mole fraction of gas, x3, and as logarithm of the Henry's law constant at de vapour pressure of water, lnKH3,12 (Pa).

The mole fractions of gas dissolved, x3, were fitted using the least-squares method to a polynomial of

Conclusions

In this paper the solubility of H2, N2, O2, CH4, C2H6, C2H4, CF4, SF6 and CO2 in the liquid mixture water + TFE at 298.15 K and 101.33 kPa partial pressure of gas have been reported. The change on the solubility with the composition of the solvent mixture increases slowly in the water-rich region.

The Gibbs energies for both the solution and the solvation processes have been calculated. At 298.15 K, the Gibbs energy for the solvation process of H2, N2, O2, CH4, C2H6, CF4 and CO2 shows clearly a

Acknowledgements

The authors thank the financial support of MICINN-FEDER (Project CTQ2009-14629-C02-02); Diputación General de Aragón (GA-LC-042/2010 La Caixa) and Departamento de Ciencia, Tecnología y Universidad del Gobierno de Aragón-Fondo Social Europeo (Grupo E52).

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  • Cited by (2)

    • Solubility of gases in fluoroorganic alcohols. Part III. Solubilities of several non-polar gases in water + 1,1,1,3,3,3-hexafluoropropan-2-ol at 298.15 K and 101.33 kPa

      2019, Journal of Chemical Thermodynamics
      Citation Excerpt :

      For example, solubilities provide information about the solvophobicity of the liquid solvent [1] and also allow an estimation of certain molecular parameters of the solvent, such as those of the Lennard-Jones potential [2]. For this reason, our research group has focused on measuring the solubility of a wide set of nonpolar gases (He, Ne, Ar, Kr, Xe, H2, N2, O2, CH4, C2H6, C2H4, CF4, SF6, and CO2) in two fluoroorganic alcohols, namely, 2,2,2-trifluorethanol (TFE) and 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP) [3–5] as well as in mixtures of water and TFE [6,7] and has also reported the solubility of noble gases in mixtures of water and HFIP [8]. The liquid mixtures are very interesting because they both have been used to modulate some of the properties having an influence on the kinetics of Diels-Alder reactions [9].

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