Preparation of an A-type zeolite film on the surface of an alumina ceramic filter

Abstract

An A-type zeolite film was prepared on the outer surface of an alumina ceramic filter by repeated hydrothermal syntheses using the same sample (referred to as repeated batch synthesis). The thickness of the film was found to increase to 35 μm by precipitating the crushed zeolite crystal on the ceramic filter and to 50 μm by precipitating the crushed alumina before repeated batch synthesis. The structure and atomic composition of the zeolite film obtained were found to the same as those of the corresponding original zeolite using several spectrometric methods: X-ray diffraction (XRD), 29Si magic-angle spinning nuclear 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 silica and alumina sources. The preferred silica and alumina sources were Na 2SiO 3 and Al(OH) 3, respectively; these are different from the usual sources for the synthesis of powdery A-type zeolites.