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 (alpha)-alumina-supported Y-type FAU membranes were studied. Defect-free, pure NaYtype zeolite membranes have been synthesized and investigated for separation of equimolar CO2/N2 mixtures under dry and moist conditions at atmospheric pressure. At room temperature, the CO2 selectivity was about 31.2 for the CO2/N2 dry gas mixture with a CO2 permeance of 2.1 × 10^-8 mol/m2·Pa·s. The addition of water vapor to the feed stream decreased the permeance for both CO2 and N2 in a temperature range of 23-200 (degree) C. The existence of water vapor significantly enhanced the CO2 selectivity at 110-200 (degree) C but drastically lowered the CO2 selectivity below 80 (degree) C. At 200 (degree) C, with increasing water partial pressure, the CO2 selectivity increased and then decreased after reaching a maximum of 4.6 at a water partial pressure of 12.3 kPa.