Preparation and characterization of sodium-free nanocrystalline sodalite

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• 作者：Simon Mü ; nzer ; Jü ; rgen Caro ; Peter Behrens
• 关键词：Colloidal zeolite ; Seed crystals ; Zeolite membrane ; Two-step crystallization ; Dynamic light scattering
• 刊名：Microporous and Mesoporous Materials
• 出版年：2008
• 期刊代码：78_13871811
• 类别：ch
• 出版时间：1 April 2008
• 卷：110
• 期：1
• 页码：3-10
• 文件大小：739 K

摘要

Zeolitic membranes based on the sodalite structure are of special interest for the separation of very small atoms and molecules (He, H₂, H₂O, NH₃). The two-step technique for the preparation of zeolitic membranes requires first the synthesis of suitable nanocrystals which act as seed crystals in the second step, the preparation of membrane. This work deals with the possibilities of synthesizing crystalline nanoparticles of pure silica sodalites and of aluminosilicate sodalites with a high Si:Al ratio. In the case of silica sodalites prepared with different neutral organic molecules as structure-directing agents, preparation of nanocrystals proved difficult and was possible only with low yields in a tedious process. With the tetramethylammonium cation (TMA) as structure-directing agent, aluminosilicate sodalite with idealized framework Si:Al ratio of 5:1 can be obtained as colloidal suspensions of nanocrystalline sodalite from a clear solution. By changing the reaction conditions from hydrothermal to an open reaction system, it is possible to generate sodalite nanocrystals in high yield. The characterization of these nanoparticles was done via dynamic light scattering, X-ray powder diffraction and high resolution scanning electron microscopy. The aluminosilicate sodalite nanocrystals thus produced can be used as seed crystals in the preparation of silica sodalite crystals with varying Si:Al ratios.