High-pressure CO2/N2 and CO2/CH4 separation using dense polysulfone-supported ionic liquid membranes

Abstract

Four ionic liquids (ILs) were blended with polysulfone (PSF) to produce functional dense polymer-supported IL membranes (DPSILMs). The main aim was to investigate the applicability of the DPSILMs in industrial gas processing applications for high-pressure CO2 separation from N2 and CH4 streams with less or no IL loss. The DPSILMs showed a clear chemical and physical change in the PSF structure and a good IL distribution in PSF. CO2/N2 and CO2/CH4 binary mixtures (5�mol% CO2) were used. The highest CO2/N2 selectivities were 36 for PSF-0.5�wt% [DIP-C4mim][NTf2] and PSF-25�wt% [N4441][formate], and 29 and 21 for PSF-0.5�wt% [C4mim][NTf2] and PSF-50�wt% [P4441][formate], respectively. The highest CO2/CH4 selectivities were 70, 63, 47, and 32 for PSF-2.5�wt% [C4mim][NTf2], PSF-2.5�wt% [DIP-C4mim][NTf2], PSF-0.5�wt% [N4441][formate], and PSF-5 wt% [P4441][formate], respectively. Another system was used to measure the permeability of each gas for plotting on the Robeson's upper bound. The DPSILMs afforded satisfying results and behave as well or better than reported PSF blends. DPSILMs with 5�wt% [P4441][formate] and [N4441][formate] showed ?30% and 20% IL loss, respectively, at 10�bar after 12�h, while no loss was observed for [DIP-C4mim][NTf2] and [C4mim][NTf2].