Preparation and characterization of Ag+ ion-exchanged zeolite-Matrimid®5218 mixed matrix membrane for CO2/CH4 separation

Abstract

In this work, the zeolite-Y was ion-exchanged by introducing silver cations into the framework of micro-sized nano-porous sodium zeolite-Y using a liquid-phase ion exchanged method. The Ag+ ion-exchanged zeolite, was then embedded into the Matrimid®5218 matrix to form novel mixed matrix membranes (MMMs). The particles and MMMs were characterized by ultraviolet-visible diffuse reflectance spectroscopy (UV–vis DRS), N2 adsorption–desorption isotherm, X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscopy (SEM). Furthermore, the effects of filler content (0–20 wt%) on pure and mixed gas experiments, feed pressure (2–20bar) and operating temperature (35–75ºC) on CO2/CH4 transport properties of Matrimid/AgY MMMs were considered. Characterization results confirmed an appropriate ion-exchange treatment of the zeolites. The SEM results confirmed the superior interfacial adhesion between polymer and zeolites, particularly in the case of Matrimid/AgY membranes. This is due to the proper silverous zeolite/Matrimid functional groups’ interactions. The gas permeation results showed that the CO2 permeability increased about 123%, from 8.34 Barrer for pure Matrimid to 18.62 Barrer for Matrimid/AgY (15 wt%). The CO2/CH4 selectivity was improved about 66%, from 36.3 for Matrimid to 60.1 for Matrimid/AgY (15 wt%). The privileged gas separation performance of Matrimid/AgY (15 wt%) was the result of a combined effect of facilitated transport mechanism of Ag+ ions as well as the intrinsic surface diffusion mechanism of Y-type zeolite. In order to survey the possibility of using the developed MMMs in industry, the CO2-induced plasticization effect and mixed gas experiment were accomplished. It was deduced that the fabricated MMMs could maintain the superior performance in actual operating conditions.