1-ethyl-3-methylimidazolium chloride plus imidazole deep eutectic solvents as physical solvents for remarkable separation of H2S from CO2

The selective removal of H2S from CO2-contained gaseous mixture is an important and challenging task for natural gas industry. Herein, 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) + imidazole DESs were examined as the physical solvents for H2S and CO2 absorption. The solubilities of gases were determined systematically, and the Henry's constants of gases, ideal selectivities of gas pair, enthalpy changes of gas absorption were calculated. The variations of H2S and CO2 solubilities with [Emim]Cl contents in DESs show different trends. In addition, the H2S solubilities in the [Emim]Cl + imidazole DESs are much higher than those of CO2. The results were compared with other liquid solvents, and [Emim]Cl + imidazole DESs enable extremely high efficiency for H2S absorption and large selectivity towards CO2. The molecular dynamics (MD) simulations and density functional theory (DFT) calculations were then systematically carried out to explain the results obtained. It is demonstrated that the strong interaction was found between the H of H2S and Cl− of [Emim]Cl, which contributes to the excellent performance of [Emim]Cl + imidazole DESs in separation of H2S from CO2.