Multilayer hydroxy sodalite zeolite membranes were synthesized on the outer surface of support with and without modification via in situ and secondary growth hydrothermal synthesis methods. The synthesized zeolite membranes were characterized by X-ray diffraction, scanning electron microscopy, and single gas (H 2 , N 2 , and n-pentane) permeation measurements at different pressure differences. The membranes synthesized by secondary growth method on the modified support were found to be highly intergrown, but the permeation results for hydrogen and n-pentane at a temperature of 323 K were not repeatable, which can be related to the weak interaction between zeolite layer and substrate. High performance hydroxy sodalite zeolite membrane was successfully formed on a nonmodified α-Al 2 O 3 support by in situ hydrothermal synthesis method. No permeance of n-pentane was measured for this membrane at 323 K and 2 bar so that infinite permselectivity of H 2 /n-C 5 H 12 could be obtained for the four-layer synthesized membrane on the nonmodified support, verifying the synthesis of a good quality hydroxy sodalite zeolite membrane. Figure 10. Scanning electron microscope (SEM) micrographs of surface (left side) and cross-section (right side) of the synthesized sodalite membrane layers on the nonmodified support; (a) monolayer, (b) two-layer by in situ method, (c) two-layer by secondary growth, and (d) three-layer by in situ methods. This figure is available in colour online at www.apjChemEng.com.

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