Synthesis of Defect-Free FAU-Type Zeolite Membranes and Separation for Dry and Moist CO₂/N₂ Mixtures

In this paper, the effects of synthesis conditions, including the seeding approach, gel composition, and hydrothermal treatment process, on the quality of porous α-alumina-supported Y-type FAU membranes were studied. Defect-free, pure NaY-type zeolite membranes have been synthesized and investigated for separation of equimolar CO 2 /N 2 mixtures under dry and moist conditions at atmospheric pressure. At room temperature, the CO 2 selectivity was about 31.2 for the CO 2 /N 2 dry gas mixture with a CO 2 permeance of 2.1 × 10 -8 mol/m 2 ·Pa·s. The addition of water vapor to the feed stream decreased the permeance for both CO 2 and N 2 in a temperature range of 23−200 °C. The existence of water vapor significantly enhanced the CO 2 selectivity at 110−200 °C but drastically lowered the CO 2 selectivity below 80 °C. At 200 °C, with increasing water partial pressure, the CO 2 selectivity increased and then decreased after reaching a maximum of 4.6 at a water partial pressure of 12.3 kPa.