The separation of CO2 using Y-type zeolite membranes ion-exchanged with alkali metal cations

NaY-type zeolite membranes, which were synthesized on the outer surface of a porous alpha -alumina tube by a hydrothermal process, were ion-exchanged with 0.1 mol l(-1) solutions of either KCL, RbCl or CsCl. The degrees of ion-exchange were 62, 40 and 32% for IC, Rb and Cs, respectively. Permeation properties of the ion-exchanged zeolite membranes were investigated at 35 degreesC for single-component and binary mixture systems of CO2 and N-2. The CO2/N-2 selectivity for the equimolar mixture was in the order: Rb = K > Cs > Na. The sorptivities of CO2 and N-2 onto the zeolites were also determined from sorption isotherms for the single-component and binary-mixture systems at 35 degreesC. The CO2/N-2 sorption selectivity was higher for the binary mixture systems than that for the single-component systems, and this was the major reason for the increase in permeation selectivity for the mixed feed. (C) 2001 Elsevier Science B.V. All rights reserved.