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

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 (2–20 bar) and operating temperature (35–75 ºC) 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.

Schematic representation of CO2 facilitated transport via Ag+ ions located at the external and internal surfaces of zeolite Y. Figure optionsDownload as PowerPoint slide