A high mordenite product was obtained from a natural raw material, diatomite, either with or without the presence of diethanolamine. The synthesis process took 2 days, and was carried out under hydrothermal conditions, at autogenic pressure, and at a temperature of 180• C. The resulting crystals were identified as mordenite by X-ray diffraction and characterized by scanning electron microscopy, and differential thermal and gravimetric analyses.
A highly crystalline ZSM-5 product was obtained from diatomite, a natural raw material, both with and without the presence of diethanolamine. The synthesis process took 40 h, and was carried out under hydrothermal conditions, at autogenic pressure, and at a temperature of 180• C. The resulting crystals were identified as ZSM-5 by X-ray diffraction and characterized by scanning electron microscopy, infrared spectroscopy, thermal gravimetry and differential thermal analysis. 2004 Society of Chemical Industry Keywords: ZSM-5; zeolite; diatomite; synthesis
INTRODUCTIONSince the synthesis of the first high-silica zeolites, β and ZSM-5, was achieved, high-silica molecular sieves have attracted attention and triggered major research efforts both in industry and academia.1 The ZSM-5 catalysts are industrially important for their thermal stability, acidity and shape-selective properties. In addition, they also have applications in oil refining, the petro-chemical industry and environmental catalysis.2 -6 The framework of the ZSM-5 zeolite contains two perpendicularly intersecting channel systems; one is sinusoidal and the other is straight. The sinusoidal system runs parallel to (001) and has near circular pore openings with free dimensions varying from 0.54 nm to 0.56 nm. The straight system runs parallel to (010) and has an elliptical shape with dimensions ranging from 0.51 nm to 0.54 nm.Zeolites are predominantly prepared from commercial reagents; 7 -11 their preparation from natural reagents is less frequent. In this paper we report the synthesis of the ZSM-5 zeolite from a natural raw material named diatomite. Diatomite is a fine-grained biogenic siliceous sediment. It consists of amorphous silica derived from opalescent skeletons of diatoms.
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