Density, Viscosity, and Hydrogen Sulfide Solubility of the Triethylamine Hydrochloride Ferric Chloride Ionic Liquid

The density, viscosity, and hydrogen sulfide solubility of the triethylamine hydrochloride ferric chloride ionic liquid (rFeCl3/Et3NHCl) were measured at temperatures of 303.15 to 348.15 K, pressures up to 200 kPa, and iron–amine ratios (r, molar ratio of anhydrous FeCl3 to Et3NHCl) of 0.4 to 1.0 mol·mol–1. Density and viscosity data were respectively fitted with empirical correlations for temperature. The H2S solubility in rFeCl3/Et3NHCl was measured by the isochoric pressure drop method. The absorption of H2S in FeCl3/Et3NHCl contains the physical process and chemical process. The decrease in temperature and iron–amine ratio and the increase in pressure are beneficial to improve the total solubility of H2S. Using the reaction equilibrium thermodynamic model (RETM) to correlate the solubility data, the chemical reaction equilibrium constant and Henry's constant were obtained. Affected by the molecular molar volume and acidity, Henry's constant first decreases and then increases with the increase in iron–amine ratio and has a minimum value at 0.6 molar ratio. The reaction equilibrium constant decreases with the rise of iron–amine ratio and the reduction of temperature. The total solubility at low pressure is dominated by chemical absorption. As the pressure increases, the proportion of physical absorption increases.