Gas permeation properties of ion‐exchanged faujasite‐type zeolite membranes

NaY‐type zeolite membranes were synthesized on a porous support tube by a hydrothermal process. The membranes were ion‐exchanged with Li+ and K+ ions, and permeances through the membranes were determined for an equimolar mixture of CO2 and N2, as well as for single‐components thereof, at a temperature range of 0–400°C. The permeance to CO2 showed a maximum at 100°C, but CO2/N2 selectivity decreased with increasing temperature. The zeolite membranes that were exchanged with K+ and Li+ ions gave higher and lower CO2/N2 selectivities, respectively, than were found for the NaY‐type membrane. The permeation properties of the ion‐exchanged zeolite membranes were analyzed using a sorption–diffusion model. The high CO2/N2 selectivity of the K‐exchanged membranes can be explained by the decrease in N2 sorptivity for the mixed feed.