Syntheses of zeolite beta films in fluoride media and investigation of their sorption properties.
Zeolite beta films were synthesized on glass slides and silicon wafers using the secondary growth method. The hydrothermal synthesis was performed in fluoride media with a wide variation of synthesis parameters. The kinetics of crystal growth under different conditions was studied, and film thicknesses ranging between 0.7 and 40 microm were obtained. A synthesis at 160 degrees C for 9 days was found to be the best compromise between the duration and the temperature of crystallization, providing films with thickness of 40 microm. Grazing incidence X-ray diffraction (GID) combined with scanning electron microscopy (SEM) analysis revealed the formation of highly crystalline, randomly oriented films. Sorption capacities and kinetics of the films and corresponding powders were studied toward several organic adsorbents (cyclohexane, n-hexane, p-xylene, trimethylbenzene, tetramethoxysilane). It was found that the adsorbed quantity depends both on the kinetic diameter and on the shape of the molecule, while the sorption capacity of the zeolitic films was estimated to be 7.14 mmol g(-1) of zeolite by nitrogen sorption tests. Kinetics data showed that the adsorption was faster on zeolite powders compared to corresponding films, revealing the presence of additional diffusion barriers in the intergrown layers.
Jakob
Alexandra
A
Laboratoire de Matériaux & Porosité Contrôlée, UMR-7016 CNRS, ENSCMu, Université de Haute Alsace, 3, rue Alfred Werner, 68093 Mulhouse Cedex, France.
Valtchev
Valentin
V
Soulard
Michel
M
Fayes
Delphine
D