Natural gas purification using supported ionic liquid membrane

This paper examines the possibility of the application of a supported ionic liquid membrane (SILM) for natural gas purification. The ionic liquid (IL) 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate (lemini][FAPI) was impregnated successfully in the y-alumina layer of a tubular porous asymmetric membrane. The pure gas permeability of natural gas components, such as carbon dioxide (CO2), methane (CH4), ethane (C2H6) and propane (C3H8) were tested through the SILM at a transmembrane pressure of 0.7 MPa and temperature of 313 K. The following trend of pure gas permeability was observed for the SILM in this study: P-co2 > P-CH4 > P-C2H6 > P-C3H8. Moreover, the CO2/CH4 ideal permselectivity was calculated. Mixed gas permeability and permselectivity for the binary mixture of CO2/CH4 (50/50%, v/v) was also measured. The mixed gas permselectivity (a 1.15) was found to be much lower than the ideal permselectivity (a 3.12). The performance of the SILM was significantly affected by the presence of water, which is also generally present in natural gas. Even though [emiml [PAP] is an excellent alternative absorbent with high CO2 absorptive capacity and ideal solubility selectivity for CO2/CH4 (5 9.69), the incorporation of this IL in a SILM is less promising for the removal of CO2 from natural gas streams, because the permselectivity for CO2/CH4 is low. (C) 2015 Elsevier By. All rights reserved.