Mixed matrix membranes for CO₂/CH₄ separation : effects of various zeolites incorporated into cellulose acetate

Abstract

Mixed matrix membranes (MMMs) comprised of molecular sieves in a polymer matrix have the potential to provide economical as well as high-performance gas separation. They combine the advantages of both materials: the processability of polymers and the superior gas transport properties of molecular sieves. MMMs have been successfully fabricated in this study by individually incorporating NaX, NaY, Silicalite, NaA, AgA, and Beta zeolites into cellulose acetate (CA) polymers following the solution-casting method. CO₂ and CH₄ permeances were determined using single gas measurements. The results showed that the gas permeance and CH₄/CO₂ selectivity were decreased as zeolite loading was increased for the MMMs incorporated with AgA, NaA, and CaA, while such phenomena were insignificantly observed for the other types of zeolite used. However, the enhancement of CO₂/CH₄ selectivity for NaX-CA MMMs was attributed to the high CO₂ sorption capacity of NaX. In comparison of CO₂/CH₄ separation performance of NaA-CA and CaA-CA MMMs, it can confirm that the partial pore blockage of zeolites by the polymer chains and polymer chain rigidification play significant roles in the gas separation performance of MMMs