Amine‐impregnated natural zeolite as filler in mixed matrix membranes for CO2/CH4 separation

Abstract

ABSTRACTFlat 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 N2 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 (Tg) and mixed‐gas transport properties. In this regard, a decreasing trend of the Tg 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 CO2 permeability (22.79 Barrer) and 55% on the CO2/CH4 selectivity (45.78) in comparison with the polymeric membrane (CO2 permeability 17.34 Barrer; CO2/CH4 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.