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The Presence of Functional Groups Key for Biodegradation in Ionic Liquids: Effect on Gas Solubility

Authors

  • Yun Deng,

    1. Laboratoire de Thermodynamique des Solutions et des Polymères, CNRS/Université Blaise Pascal, Clermont-Ferrand, 24, avenue des Landais, 63177 Aubière Cedex (France), Fax: (+33) 473405328
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  • Saibh Morrissey,

    1. School of Chemical Sciences and National Institute for Cellular Biotechnology, Dublin City University, Glasnevin, Dublin 9 (Ireland)
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  • Nicholas Gathergood Dr.,

    1. School of Chemical Sciences and National Institute for Cellular Biotechnology, Dublin City University, Glasnevin, Dublin 9 (Ireland)
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  • Anne-Marie Delort Dr.,

    1. Synthèse et Etudes de Systèmes à Intérêt Biologique, CNRS/Université Blaise Pascal, Clermont-Ferrand, 24, avenue des Landais, 63177 Aubière Cedex (France)
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  • Pascale Husson Dr.,

    1. Laboratoire de Thermodynamique des Solutions et des Polymères, CNRS/Université Blaise Pascal, Clermont-Ferrand, 24, avenue des Landais, 63177 Aubière Cedex (France), Fax: (+33) 473405328
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  • Margarida F. Costa Gomes Dr.

    1. Laboratoire de Thermodynamique des Solutions et des Polymères, CNRS/Université Blaise Pascal, Clermont-Ferrand, 24, avenue des Landais, 63177 Aubière Cedex (France), Fax: (+33) 473405328
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Abstract

The effect of the incorporation of either ester or ester and ether functions into the side chain of an 1-alkyl-3-methylimidazolium cation on the physico-chemical properties of ionic liquids containing bis(trifluoromethylsulfonyl)imide or octylsulfate anions is studied. It is believed that the introduction of an ester function into the cation of the ionic liquids greatly increases their biodegradability. The density of three such ionic liquids is measured as a function of temperature, and the solubility of four gases—carbon dioxide, ethane, methane, and hydrogen—is determined between 303 K and 343 K and at pressures close to atmospheric level. Carbon dioxide is the most soluble gas, followed by ethane and methane; the mole fraction solubilities vary from 1.8×10−3 to 3.7×10−2. These solubilities are of the same order of magnitude as those determined for alkylimidazolium-based ionic liquids. The chemical modification of the alkyl side chain does not result in a significant change of the solvation properties of the ionic liquid. All of the solubilities decrease with increasing temperature, corresponding to an exothermal solvation process. From the variation of this property with temperature, the thermodynamic functions of solvation (Gibbs energy, enthalpy, and entropy) are calculated and provide information about the solute–solvent interactions and the molecular structure of the solutions.

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