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 (X-alumina-supported Y-type FAU membranes were studied. Defect-free, pure NaY-type zeolite membranes have been synthesized and investigated for separation of equimolar CO2/N-2 mixtures under dry and moist conditions at atmospheric pressure. At room temperature, the CO2 selectivity was about 31.2 for the CO2/N-2 dry gas mixture with a CO2 permeance of 2.1 x (.)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 degreesC. The existence of water vapor significantly enhanced the CO2 selectivity at 110200 degreesC but drastically lowered the CO2 selectivity below 80 degreesC. At 200 degreesC, 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.