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

Abstract 1-Ethyl-3-methylimidazolium hexafluorophosphate ([Emim][PF 6 ]) was incorporated into poly(amide-6- b -ethylene oxide) (Pebax1657) to prepare blend membranes. The physical properties of Pebax1657/[Emim][PF 6 ] blend membranes were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). For Pebax1657/[Emim][PF 6 ] blend membranes, the melting peak of polyether (PE) segment disappeared when [Emim][PF 6 ] content reached 10 wt%, and the melting peak of [Emim][PF 6 ] appeared until [Emim][PF 6 ] content came up to 60 wt%, indicating the homogeneous mixing of [Emim][PF 6 ] and Pebax1657 for the prepared Pebax1657/[Emim][PF 6 ] blend membranes. According to FTIR, some interactions were formed between [Emim][PF 6 ] and PE segment. The gas transport properties of CO 2 , N 2 , CH 4 and H 2 for Pebax1657/[Emim][PF 6 ] blend membranes were also investigated. The incorporation of [Emim][PF 6 ] increased the gas solubility coefficients of CO 2 , N 2 , CH 4 and H 2 , however the gas diffusion coefficients decreased, which led to the decrease of the permeabilities of CO 2 , N 2 , CH 4 and H 2 . Meanwhile, the selectivity of CO 2 /CH 4 increased slightly. With the increase of temperature (35–85 °C), the solubility coefficient of CO 2 decreased, while the diffusion coefficients of CO 2 , N 2 , CH 4 and H 2 increased, resulting into the increase of the permeabilities of CO 2 , N 2 , CH 4 and H 2 . Moreover, no sharp increase of gas permeability was observed at the melting point of [Emim][PF 6 ] (60 °C). And the activation energies of permeation of CO 2 , N 2 , CH 4 and H 2 increased with increasing [Emim][PF 6 ] content.