Incorporation of an ionic liquid into a midblock-sulfonated multiblock polymer for CO2 capture

Abstract

In the present work, hybrid block ionomer/ionic liquid (IL) membranes containing up to 40 wt% IL are prepared by incorporating 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) into a midblock-sulfonated pentablock polymer (Nexar) that behaves as a thermoplastic elastomer. Various analytical techniques, including thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR) spectroscopy, small-angle X-ray scattering (SAXS), and water sorption have been employed to characterize the resultant membrane materials. Single- and mixed-gas permeation tests have been performed at different relative humidity conditions to evaluate membrane gas-separation performance and interrogate the molecular transport of CO2 through these membranes. Addition of IL to Nexar systematically enhances CO2 permeability through membranes in the dry state. Introduction of water vapor into the gas feed further promotes CO2 transport, yielding a maximum permeability of 194 Barrers and a maximum CO2/N2 selectivity of 128 under different test conditions. These results confirm that humidified Nexar/IL hybrid membranes constitute promising candidates for the selective removal, and subsequent capture, of CO2 from mixed gas streams to reduce the environmental contamination largely responsible for global climate change.