Selective separation of H2S and CO2 from CH4 by supported ionic liquid membranes

Abstract Supported ionic liquid membranes (SILMs) are considered as promising media for the upgrading of natural gas. However, most research has focused on the selective separation of CO 2 and CH 4 , paying little attention to the selective separation of H 2 S and CH 4 or H 2 S and CO 2 in SILMs. In this work, the permeability of CH 4 , CO 2 , and H 2 S in two different categories of ionic liquids (neutral and basic ionic liquids) were systemically investigated under dry conditions. The ideal selectivity of CO 2 /CH 4 , H 2 S/CH 4 , and H 2 S/CO 2 were calculated. The effect of anion species, transmembrane pressure difference, and temperature on the permeability of single gas and ideal selectivity of gas pairs were studied. It is found that neutral ionic liquids (1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-3-methylimidazolium trifluoromethanesulfonate) show high permeability of CO 2 and H 2 S, and competitive permselectivity of CO 2 /CH 4 and H 2 S/CH 4 , and thus can be used for the simultaneous removal of H 2 S and CO 2 from natural gas. Basic ionic liquids (1-butyl-3-methylimidazolium acetate) show not only high permeability of CO 2 and H 2 S, but also superior permselectivity of CO 2 /CH 4 , H 2 S/CH 4 and H 2 S/CO 2 , and thus can be potentially used for selective removal of H 2 S from natural gas. Moreover, facilitated transport of H 2 S and CO 2 were observed in 1-butyl-3-methylimidazolium acetate. To the best of our knowledge, this is the first time that the facilitated transport of H 2 S in SILMs is reported.