Blend membranes of poly(amide-6-b-ethylene oxide)/[Emim][PF6] for CO2 separation

1-Ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF6]) was incorporated into poly(amide-6-b-ethylene oxide) (Pebax1657) to prepare blend membranes. The physical properties of Pebax1657/[Emim][PF6] blend membranes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). For Pebax1657/[Emim][PF6] blend membranes, the melting peak of polyether (PE) segment disappeared when [Emim][PF6] content reached 10 wt%, and the melting peak of [Emim][PF6] appeared until [Emim][PF6] content came up to 60 wt%, indicating the homogeneous mixing of [Emim][PF6] and Pebax1657 for the prepared Pebax1657/[Emim][PF6] blend membranes. According to FTIR, some interactions were formed between [Emim][PF6] and PE segment. The gas transport properties of CO2, N2, CH4 and H2 for Pebax1657/[Emim][PF6] blend membranes were also investigated. The incorporation of [Emim][PF6] increased the gas solubility coefficients of CO2, N2, CH4 and H2, however the gas diffusion coefficients decreased, which led to the decrease of the permeabilities of CO2, N2, CH4 and H2. Meanwhile, the selectivity of CO2/CH4 increased slightly. With the increase of temperature (35-85 °C), the solubility coefficient of CO2 decreased, while the diffusion coefficients of CO2, N2, CH4 and H2 increased, resulting into the increase of the permeabilities of CO2, N2, CH4 and H2. Moreover, no sharp increase of gas permeability was observed at the melting point of [Emim][PF6] (60 °C). And the activation energies of permeation of CO2, N2, CH4 and H2 increased with increasing [Emim][PF6] content.