Journal of Membrane Science, Vol.208, No.1-2, 415-418, 2002
Influence of alkali cations on permeation properties of Y-type zeolite membranes
NaY-type zeolite membranes were synthesized on the outer surface of an alpha-alumina support tube by a hydrothermal process. The membranes were ion-exchanged with 0.01-0.50 mol/l aqueous solutions of KCl, RbCl or CsCl at 80degreesC for 4 h. Gas permeation properties of the ion-exchanged membranes were determined at 35degreesC for single component systems of CO2 and N-2 and for an equimolar mixture, thereof. The CO2/N-2 separation factor for permeation increased with increasing ion-exchange degree, which was dependent on the cation species. When the membrane was treated in a 0.50 mol/l solution of KCl, RbCl and CsCl, the ion-exchange degree reached 96, 78 and 62%, respectively. The CO2/N-2 separation factors of the Y-type zeolite membranes ion-exchanged with K, Rb and Cs were 55, 47 and 46%, respectively, at a permeation temperature of 35degreesC. The NaY-type zeolite membranes, which were impregnated with Cs ions, showed the highest CO2/N-2 separation factor of 140 at 35degreesC. These results suggest that the CO2/N-2 separation factor was largely determined by the affinity between the membranes and the permeants.