Separation of CO2 and H2S from natural gas of iranian gas refinery using ionic liquids: Experimental measurements and thermodynamic modeling

Separation of the acid gases and reducing their amount from natural gas is very important in the gas purification industries. In this study, the solubility of natural gas (a mixture of CO2, H2S, CH4, C2H6, etc.) was experimentally measured in three different ionic liquids: 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([Hmim] [Tf2N]), 1-hexyl-3-methylimidazolium nitrate ([Hmim][NO3]) and 1-butyl-3-methylimidazolium acetate ([Bmim][Ac]). The experimental solubility data was obtained for the temperatures of 298.15 K, 318.15 K, and 338.15 K in pressure range up to 40bar. Selectivity of CO2/CH4, CO2/H2S and H2S/CH4 in the studied ionic liquids was also reported in this work. [Bmim] [Ac] showed the best performance of absorbing CO2 and H2S compared to other ionic liquids. However, [Hmim][Tf2N] showed higher selectivity for CO2 over CH4 in comparison with [Hmim][NO3] and [Bmim][Ac]. Finally, the sPC-SAFT equation of state was successfully used to predict the natural gas solubility in ionic liquids. The results show that the model predictions are consistent with experimental data.