Amine‐impregnated natural zeolite as filler in mixed matrix membranes for CO 2 /CH 4 separation

Flat mixed matrix membranes (MMMs) comprising polysulfone and clinoptilolite‐type natural zeolite were prepared by casting. Zeolite was modified with three alkylamines: ethanolamine (EA), bis(2‐hydroxypropyl)amine (BHPA), and polyethylenimine (PEI) by the impregnation method. Impregnated zeolite samples were characterized by X‐ray diffraction, Fourier transform infrared spectroscopy, and N 2 adsorption–desorption. The alkylamine loading extent determined by thermogravimetric analysis was 5.2, 4.8, and 8.5% for EA, BHPA, and PEI, respectively. Analyses of MMMs showed that the incorporation of impregnated zeolite affected the glass‐transition temperature ( T g ) and mixed‐gas transport properties. In this regard, a decreasing trend of the T g values from 185.5 °C for the polymeric membrane up to 176.6 °C for Clino‐EA‐based MMM was recorded. In addition, the gas separation performance was evaluated at two different feed pressures. At 50 psi, MMMs showed an enhancement up to 30% on the CO 2 permeability (22.79 Barrer) and 55% on the CO 2 /CH 4 selectivity (45.78) in comparison with the polymeric membrane (CO 2 permeability 17.34 Barrer; CO 2 /CH 4 selectivity 29.38). These values varied depending on the alkylamine, BHPA being the most selective. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48286.