Treatment of calcined MSU-S with NaAlO₂ solution in the presence of CTAB: Change of acidic and catalytic properties

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• 作者：Shangru Zhai ; Junlin Zheng ; Junping Li ; Dong Wu ; Yuhan Sun and Feng Deng
• 关键词：Mesoporous materials ; MSU-S ; Synthesis ; Modification ; Catalysis
• 刊名：Microporous and Mesoporous Materials
• 出版年：2005
• 期刊代码：78_13871811
• 类别：ch
• 出版时间：2005
• 卷：83
• 期：1-3
• 页码：10-18
• 文件大小：641 K

摘要

A hydrothermal post-synthesis modification method is introduced as a convenient but efficient route to improve aluminum content and acid amount of hexagonal MSU-S by treatment of it with NaAlO₂ solution in the presence of cationic cetyltrimethylammonium bromide (CTAB) under hydrothermal conditions. The speciality of this post-synthesis method, as compared with those reported studies on post-synthesis of Al-containing mesoporous materials, was that it took advantage of the hydrothermally unstable character of silica/aluminosilicate based mesoporous materials which would be partially dissolved in this highly-basic system and the templating function of CTAB. Indeed, characterization results based on a series of techniques (XRD, SEM, TEM, ICP elemental analysis, DSC, ²⁷Al-NMR, FTIR and NH₃-TPD) clearly proved that CTAB added in this modification process played a crucial role in the introduction of Al into the final solids via self-assembly with additionally introduced and partly dissolved silicates from the parent MSU-S particles. In this way, Al amount determined by ICP and ²⁷Al-NMR, acid content measured by NH₃-TPD and therefore catalytic performance of the resultant samples characterized by cumene cracking were substantially improved in comparison with the parent MSU-S. It was also found that, if no CTAB in the modification procedure, the initial well-ordered MSU-S would be severely destroyed losing its mesoporous feature.