期刊
MICROPOROUS AND MESOPOROUS MATERIALS
卷 112, 期 1-3, 页码 561-572出版社
ELSEVIER
DOI: 10.1016/j.micromeso.2007.10.037
关键词
mesoporous silica spheres; silicalite-1; zeolite coating; hollow zeolite spheres; adsorption
The formation process of hollow silicalite-1 spheres by liquid phase hydrothermal synthesis has been studied in a number of synthesis conditions: temperatures from 90 to 175 degrees C and times from 0.5 to 24 h. The starting material for this was mesoporous silica spheres (seeded with silicalite-1 nanocrystals), which were converted to zeolite in a solution containing an optimum amount of TEOS as silica source to minimize the number of non-completed hollow silicalite-1 spheres and at the same time agglomeration. The possible presence of non-converted silica in the synthesized hollow silicalite-1 spheres is Suggested by Si-29 NMR, even though this was not evidenced by SEM, XRD, FTIR and TEM characterization. A N-2 adsorption analysis carried out on the samples reveals the presence of external surface area in all the hollow silicalite-1 spheres prepared. This external surface area could be attributed to non-converted silica but also to intercrystalline voids in the hollow synthesized silicalite-1 particles, and to non-evolved silicalite-1 seeds. Preliminary thermogravimetric experiments involving water, n-hexane, triisopropylbenzene and 2,2-dimethylbutane molecules lead to a consideration of important adsorption features related to the hollow silicalite-1 spheres. (C) 2007 Elsevier Inc. All rights reserved.
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