Systematic study of the influence of the molecular structure of fluorinated ionic liquids on the solubilization of atmospheric gases using a soft-SAFT based approach

Autors/es

Ferreira, M.L.; Llovell, F.; Vega, L.F.; Pereiro, A.B.; Araújo, J.M.M.

Abstract

This work focuses on the design and development of fluorinated ionic liquids (FILs) as alternatives to perfluorocarbons (PFCs), widely used in industrial applications. A combined theoretical-experimental approach has been used to characterize ionic liquids (ILs), considering their thermodynamic behaviour in the presence of atmospheric gases (oxygen (O₂), nitrogen (N₂) and carbon dioxide (CO₂)). The selected ILs are based on perfluorobutanesulfonate ([C₄F₉SO₃]⁻), perfluoropentanoate ([C₄F₉CO₂]⁻), trifluoromethanesulfonate ([CF₃SO₃]⁻) and trifluoroacetate ([CF₃CO₂]⁻) anions, combined with imidazolium ([C_nC₁Im]⁺, n = 2 and 4) and pyridinium ([C₂C₁py]⁺) cations. The soft-SAFT (Statistical Associating Fluid Theory) molecular-based equation of state has been used to determine the solubility behaviour of atmospheric gases in the ILs. Models for three FILs not yet parametrized, [C₂C₁py][C₄F₉SO₃], [C₂C₁Im][C₄F₉CO₂] and [C₂C₁py][C₄F₉CO₂], have been built from transferable molecular models. The solubility of O₂, N₂ and CO₂ in the ILs has been determined, in excellent agreement with experimental data, indicating the robustness of the soft-SAFT approach. The highest solubilities have been obtained for the FILs based on the perfluorobutanesulfonate anion ([C₄F₉SO₃]⁻) combined with 1-ethyl-3-methylpyridinium cation ([C₂C₁py]⁺) and 1-butyl-3-methylimidazolium cation ([C₄C₁Im]⁺). This approach grants to evolve highly predictive IL models inherently, regarding the process of parametrization from the molecular structure, which allows to describe the behaviour of these complex systems in a faster and more robust way.