The novel micro-phase separated CO2-selective mixed matrix membranes (MMMs) modified with ester group by EPEG

Abstract In this paper, ethyl phthalyl ethyl glycolate (EPEG) was first introduced into Pebax to prepare Pebax/EPEG MMMs for CO2 separation. The thermal properties and the gas permeation properties of the MMMs were investigated. The micro-nano structure of the MMMs and the interaction between Pebax and EPEG were studied with fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). The compatibility of Pebax and EPEG was characterized with FTIR-mapping and DSC. The location and distribution of liquid EPEG was studied with SEM and confirmed visually by cryo-SEM. The strength of hydrogen bonding interaction in the MMMs was characterized by Kwei equation with a parameter q. Pebax and EPEG were almost miscible in the MMMs at the molecular level when the EPEG content was not higher than 20 wt%, and then micro-phase separation happened at higher EPEG content. The incorporation of EPEG not only enhanced the diffusion coefficients but also the solubility coefficients of the penetrants through the MMMs. The occurrence of micro-phase separation rendered a greater degree of permeability increase. For the MMMs with EPEG content of 60 wt%, the CO2 permeability was almost 400 Barrer companied with CO2/N2 selectivity of 30. The CO2 permeability was three times that of the pristine Pebax, indicating the good CO2/N2 separation performance of Pebax/EPEG MMMs.