Low viscous Protic ionic liquids functionalized with multiple Lewis Base for highly efficient capture of H2S

Three kinds of aqueous multiple Lewis base functionalized protic ionic liquids (MLB-PILs) solutions are designed for highly efficient absorption of H2S. These MLB-PILs are tethered with tertiary amine groups on their cations and acetate as anions. 1H NMR, 13C NMR spectra, their physical properties (e.g. densities and viscosities) and thermal properties are carefully characterized. Impressively, the viscosities of MLB-PILs are <25 cP at ambient temperature, which is obviously lower than other ILs reported in literature. The H2S solubility of MLB-PILs are superior compared with other reported H2S absorbents, which can reach 0.65–1.92 mol∙mol−1 at 1 bar and 313.2 K. With the assumption of complex formation between H2S and MLB-PILs, the reaction equilibrium thermodynamic model (RETM) is adopted to correlate the experimental solubility. Basing on the fitting results, the thermodynamic parameters such as Henry's law constants H and reaction equilibrium constants K are obtained. Furthermore, the enthalpy change ∆HSOL and the entropy change ∆SSOL are also calculated to analyze the absorption process of H2S in these MLB-PILs. According to the results, the MLB-PILs are believed to have potential use in gas sweetening.