Solubility and Thermodynamic Parameters of H₂S/CH₄ in Ionic Liquids Determined by ¹H NMR

Natural gas remains an important global source of energy. Usually, sour gas from the well or refinery stream contains H₂S among other contaminants that should be removed to fulfill permissible standards of use. Despite the use of different gas–liquid sour gas upgrading technologies, ionic liquids (ILs) have been recognized as promising materials to remove H₂S from sour gas. However, data concerned with thermodynamic solution functions of H₂S in ILs have scarcely been reported in the literature. In this work, solution ¹H NMR spectroscopy was employed for quantifying H₂S soluble in [BMIM]­[Cl] and for gaining a better understanding of the H₂S–IL interaction. Experiments were carried out in a Young-Tap NMR tube containing a saturated solution of H₂S/CH₄/[BMIM]­[Cl] and recording spectra from 298 to 333 K. The thermodynamic solution functions, determined from the Van’t Hoff equation, showed that solubility of the H₂S in the [BMIM]­[Cl] is an exothermic gas–liquid physisorption process (Δ_solH° = −66.13 kJmol^–1) with a negative entropy change (Δ_solS° = −168.19 JK^–1 mol^–1). ¹H NMR spectra of the H₂S/[BMIM]­[Cl] solution show a feature of strong solute–solvent interactions. However, solubility enthalpy is a fifth of the H–S bond energy value. Results from ¹H NMR spectroscopy also agree with those from the bench dynamic experiments.