Effect of zeolite surface modification with ionic liquid [APTMS][Ac] on gas separation performance of mixed matrix membranes

Abstract

Abstract This study focuses on using a (3-aminopropyl)trimethoxysilane and acetate ion based ionic liquid to modify zeolite 4A as a filler in a polysulfone (PSf) membrane for CO2/CH4 and CO2/N2 separation, aiming at improving the polymer-filler interaction and separation performance of the mixed matrix membrane (MMM). The ionic liquid was covalently attached onto the zeolite surface. Zeolite modification was confirmed through FTIR analysis of pristine and modified filler. N2 sorption isotherms were used to characterize the porous structure, which showed decrease in surface area and pore volume after surface modification of zeolite. The crystal structure of zeolite 4A remained unaffected after modification with ionic liquid, as shown by XRD and SEM. Moreover, the synthesized PSf-based MMMs were tested in the separation of CO2 from CH4. Experiments were conducted at different temperatures and feed conditions, and pure and mixed gas permeability/selectivity data was reported. This modification of zeolites with methoxy groups containing cation and acetate anion based ionic liquid, resulted in an improved separation performance, as the modified filler enhanced the MMMs selectivity of CO2/CH4 by 37% and for CO2/N2 by 43% at 30 wt% filler loading as compared to pristine filler MMMs. The 3-(trimethoxysilyl)propan-1-aminium acetate coating acts as a selecting film which notably improves the selectivity at marginal expense of CO2 permeance.