Exploring the separation properties of high-Si CHA membranes for the CO2 capturing technology: Impact of the selective layer thickness and growth mechanism

This study investigates the influence of the CHA selective layer's thickness, coated on a mono-channel alumina support using the secondary growth method, on the performance of CO2 separation from CH4. The membrane layer's thickness was explored by adjusting the concentration and duration of the seeding process, as well as the distribution of crystal size in the suspension. Single gas analysis results revealed that utilizing smaller crystal seeds, with an average crystallite size of approximately 600 nm, exhibited the highest performance. Furthermore, a membrane thickness of 2.1 μm demonstrated an ideal CO2/CH4 permselectivity of 205 with a CO2 permeance of 2.39 x 10-6 [mol/(m2sPa)]. For the equimolar CO2 - CH4 gas mixture, the high-Si membrane displayed a CO2/CH4 selectivity of 210 with a CO2 permeance of 8.06 x 10-7 [mol/(m2sPa)]. In both gas permeation measurement, CO2 permeance exhibited a slight linear decrease with increasing thickness, while CH4 permeance initially decreased and then increased non-linearly.