Capture of H2S from binary gas mixture by imidazolium-based ionic liquids with nonfluorous anions: A theoretical study



Selective capture of H2S from gas mixture is essential to reduce its undesirable high corrosiveness and toxicity. Ionic liquids have been proposed as a promising material, and there is a need to clarify the capture mechanisms and search for optimal combination of cation and anion for application. This work aims to elucidate the interactions between H2S and nonfluorous imidazolium ionic liquids (NIILs) at a molecular level. The effects of hydroxyl group on the tail of alkyl chain, and combinations of imidazolium cations and nonfluorous anions on H2S capture are explored using quantum chemistry calculations. Furthermore, molecular dynamics simulations are used to explore the microstructural features of NIIL–H2S–CH4 mixture systems. It is found that the hydroxyl groups in the cations is essential in governing the absorption properties of NIILs, including the interaction sites for hydrogen bonding, interaction geometries and energies, diffusion coefficients, and organization of H2S and CH4 around cations and anions. A molecular viewpoint to design appropriate ionic liquids for promoting their applications for H2S capture is provided. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3824–3833, 2013