Lattice Constants of Tubular Zeolite NaA Membranes by Parallel Beam X-Ray Diffraction

A parallel beam X-ray diffraction analysis (XRD) machine equipped with a parabolic multilayer, Soller slit and long horizontal slit has been applied to tubular zeolite NaA (LTA) membranes supported by a porous alumina tube, prepared by hydrothermal synthesis for the dehydration of ethanol. The present XRD is a suitable method used to analyze tubular LTA membranes and give a sharp XRD pattern, because the sample form does not affect the diffraction angles. For lattice-constant measurements, six diffraction lines in the 2θ region of 40∼60° were used, and their diffraction angles were corrected using 220 and 311 lines of silicon powder (NIST SRM640c) as an external standard. The XRD measurements were carried out for LTA membranes after pervaporation experiments of an ethanol/water (90/10) mixture, and the observed lattice constants were 24.573∼24.599 A, corresponding to the hydrothermal synthesis condition. Thus, the lattice constants of the tubular LTA membranes were first reported.