Defects-healing of SAPO-34 membrane by post-synthesis modification using organosilica for selective CO₂ separation

It is challenging to avoid the formation of defects in zeolite membranes during their preparation. Herein, we present a facile vacuum-assisted deposition (VAD) method as a feasible solution to address this challenge. Defective SAPO-34 membranes supported on tubular porous alumina were healed using bis(triethoxysilyl)ethane (BTESE)-derived organosilica via VAD, showing an improved performance in the selective CO₂ separation from an equimolar CO₂/CH₄ mixture. Specifically, by controlling the amount of organosilica deposited, the coating was able to heal the non-selective defects in SAPO-34 membranes without compromising the CO₂ permeance, but increased the CO₂/CH₄ selectivity notably (by a factor of ca. 2.5 at 25 °C and 200 kPa). An excessive coating of organosilica by VAD resulted in a thick layer on top of the SAPO-34 membrane which led to a significant decrease in the CO₂ permeance. Additionally, a modified membrane was also investigated for the CO₂/CH₄ gas feed with different CO₂ concentrations from 20 to 50 mol.% and this showed that a relatively concentrated CO₂ in the system could improve the seperation performance of the developed membrane.