FAU-type zeolite membranes with different Si/Al ratios were hydrothermally synthesized on the outer surface of a porous α-Al2O3 support tube. The permeances of the membranes to CO2, CH4 and N2 were then measured at 308 K for single-component and equimolar binary systems. The separation properties were dependent on both the Si/Al ratio and the ion-exchange treatment. For single-component systems, a lower Si/Al ratio resulted in the incorporation of a larger number of Na(+) ions. For a CO2-CH4 mixture, both CO2 permeances and CO2/CH4 selectivities were approximately half the values obtained for a binary CO2-N2 mixture. The highest selectivities, obtained using the NaX(1) zeolite membrane, were 28 for CO2/CH4 and 78 for CO2/N2. The RbY, RbX(1) and RbX(2) zeolite membranes showed larger CO2 permeances, compared with those of the original Na-type membranes. Ion-exchange with K(+) ions was the most effective for the NaY zeolite membrane in that both the CO2 permeance and the CO2/CH4 selectivity were increased.
Jeong BH, Hasegawa Y, Kusakabe K, Morooka S, Sep. Sci. Technol., to submitted, 2001
Kita H, Asamura H, Tanak K, Okamoto K, "Preparation and Pervaporation Properties of X- and Y-Type Zeolite Membranes," ACS Symposium Series 744, Membrane Formation and Modification, American Chemical Society, Washington D.C., 330, 2000