Ultra-selective CO2/N2 separation membranes enabled by establishing delivery site-based CO2 transfer channels in Pebax membranes with PEG-montmorillonite

Abstract

Here, a new kind of mixed matrix membranes (MMMs) were fabricated using Pebax1074 as continuous polymer matrix and poly (ethylene glycol)-modified montmorillonite (PEG-MMT) as dispersive dopant. The microscopic morphology, microstructure, surface functional groups, thermal stability, thermodynamic properties, and gas adsorption behaviors of the MMMs were characterized by scanning electron microscope, x-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimeter, and N₂ and CO₂ adsorption, respectively. The effects of PEG-MMT amount, permeation temperature and permeation pressure on the microstructure and gas permeation properties of the as-prepared MMMs were mainly investigated. The results show that the interlayer spacing of MMT is increased by intercalating with PEG. The resultant PEG-MMT presents an excellent dispersion and interfacial compatibility in Pebax membranes. The microstructure of the membrane tends to become more compact as the dopant content increases in the membrane. Meanwhile, both the CO₂/N₂ selectivity and CO₂ permeability of MMMs show a trend of first growing and then descending. In addition, permeation at low pressure and low temperature is beneficial for the separation performance of the membrane for CO₂/N₂ system. Under the permeation condition of 30 °C and 0.1 MPa, an exceptional CO₂/N₂ selectivity is attained to 221.2 for the MMMs made of 2 % PEG-MMT dopant amount, along with the CO₂ gas permeability of 148.3Barrer. Overall, the present MMMs hold a promising prospect with extremely commercial attractiveness in terms of CO₂/N₂ gas separation performance.