H(2)S–CO(2) gas separation with ionic liquids on low ratio of H(2)S/CO(2)

Acid gas removal, especially H(2)S and CO(2), is an essential process in natural gas processing. In this research, 1-butyl-3-methylimidazolium bromide [bmim][Br] ionic liquid was analyzed as a hydrophobic solvent with has high selectivity to H(2)S as an environmentally friendly solvent to absorb acid gas from natural gas with low H(2)S/CO(2) concentration in ambient temperature and pressure. The absorption performance of pure [bmim][Br] ionic liquid was compared with various amine solutions, such as monoethanolamine (MEA), triethanolamine (TEA), and methyldiethanolamine (MDEA), as well as the mixture of [bmim][Br]-MDEA with various concentration. As a result, pure [bmim][Br] ionic liquid had high selectivity to H(2)S compared with conventional amine solutions. In addition, the mixture of [bmim][Br]-MDEA with the mass ratio of 1:3 provided the highest H(2)S/CO(2) selectivity of 6.2 in certain absorption conditions due to free tertiary amine attached in the cations of ionic liquids that can attract more H(2)S to its functional site.