CO2 separation by supported ionic liquid membranes and prediction of separation performance

Abstract

Four supported ionic liquid membranes (SILMs) were prepared by fixing ionic liquids (ILs) 1-butyl-3-methylimidazolium dicyanamide ([BMIM][DCA]), acetate ([BMIM][AC]), trifluoromethanesulfonate ([BMIM][TfO]) and bis ((trifluoromethyl)sulfonyl)imide ([BMIM][NTf2]), respectively, in Polyvinylidene Fluoride (PVDF) membranes and used for the separation of CO2/H2 and CO2/N2 gas mixtures. Density function theory (DFT) calculations were performed to predict the complexation energy (EC) between the ILs and CO2, H2 and N2 molecules as well as the gas separation performance of their SILMs. Experimental results indicate that the gas permeation rate of the SILMs increases with increasing temperature. [BMIM][TfO] SILM showed the best separation performance for CO2/H2 with permselectivity of 16.2 and CO2 permeability of 1966 Barrer at 40°C. [BMIM][AC] SILM showed the best separation efficiency for CO2/N2 with permselectivity of 21.8 and CO2 permeability of 520 Barrer at 30°C. The separation capacity of SILMs for the CO2/H2 and CO2/N2 follows the increasing order of the Ec differences.