Enhanced Natural Gas Sweetening with Ultralow H₂S Concentration via Polycarbonate-Silica Mixed Matrix Membranes

Mixed matrix membranes (MMMs) are brought up as prospecting media to sweeten natural gas in recent decades. But the majority of experiments have conducted on CO₂/CH₄ gas pair separation, and H₂S removal from CH₄ through MMMs has been paid less consideration. Thereupon, polycarbonate (PC) permeability and permselectivity as a polymer with inherent gas transport properties and two PC-based MMMs containing octylsilane (OS) and polydimethylsiloxane (PDMS)-modified nanosilica were investigated under various operational conditions for this gas couple. The influence of operational parameters including transmembrane pressure, feed temperature, H₂S inlet concentration and physical aging on the permeability of mixed gas and selectivity of the H₂S/CH₄ pair was assessed. It was observed that addition of silica nanoparticles causes more H₂S permeability and selectivity. As a result, it can be used for methane upgradation. Membranes fabricated with PDMS-modified nanosilica showed the highest permeability of H₂S and also the superior selectivity of H₂S/CH₄. Therefore, it could be possibly applied to mitigation of H₂S concentration in the outlet gas stream.