PREPARATION OF AN A-TYPE ZEOLITE FILM ON THE SURFACE OF AN ALUMINA CERAMIC FILTER

An A-type zeolite film was prepared on the outer surface of an alumina ceramic filter by repeated hydrothermal syntheses using the same samp le (referred to as repeated batch synthesis). The thickness of the fil m was found to increase to 35 mu m by precipitating the crushed zeolit e crystal on the ceramic filter and to 50 mu m by precipitating the cr ushed alumina before repeated batch synthesis. The structure and atomi c composition of the zeolite film obtained were found to be the same a s those of the corresponding original zeolite using several spectromet ric methods: X-ray diffraction (XRD), Si-29 magic-angle spinning nucle ar magnetic resonance (MAS NMR) and electron-probe microanalysis (EPMA ). The morphology and thickness of the zeolite film were dependent on the reaction time and temperature, and especially on the types of sili ca and alumina sources. The preferred silica and alumina sources were Na2SiO3, and Al(OH)(3), respectively; these are different from the usu al sources for the synthesis of powdery A-type zeolites.