Formation of and silicon incorporation in SAPO-5 synthesized via dry-gel conversion
Formation of and silicon incorporation in SAPO-5 synthesized via dry-gel conversion
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DOI：
10.1016/j.micromeso.2013.08.016
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发表时间：
2013-12
影响因子：
5.2
通讯作者：
Adam R. MacIntosh;Yining Huang
中科院分区：
文献类型：
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作者：
Adam R. MacIntosh;Yining Huang
分子筛自发现以来一直是科学和工业上重要的材料。这些由氧桥连的四面体配位原子的多孔结晶网络被认为是优异的催化剂。铝磷酸盐类分子筛的骨架本身是非催化的，但是通过杂原子取代，这些材料可以多样化为例如硅铝磷酸盐（SAPO）类非均相酸催化剂。研究这些替代发生的方法，因为发现可以导致对材料性质和功能的精确控制。以SAPO-5为模型体系，采用27 Al、29 Si、31 P固体核磁共振和PXRD等方法对SAPO-5进行了研究。SAPO-5研究确定蒸汽辅助转化（SAC）和气相传输（VPT）的干凝胶转化（DGC）方法遵循类似的反应途径。在由VPT方法的凝胶中缺乏有机结构导向剂引起的初始差异之后，方法之间的结晶是相似的，并且硅掺入导致两个硅位点群体。一个代表孤立的Si（OAl）4物种很好地纳入框架，而另一个代表硅岛的框架内。核的初始核心是AlPO 4的性质和Si逐渐纳入晶格的晶体生长。汽相硅吸收（VPSU）方法提供了一个对比，这一数据，诱导成核，同时发生与硅掺入和生产仅隔离的Si（OAl）4物种。
Molecular sieves have been scientifically and industrially important materials since their discovery. These porous, crystalline networks of tetrahedrally coordinated atoms bridged by oxygen are known as excellent catalysts. The framework of the aluminophosphate family of molecular sieves is itself non-catalytic, but through heteroatomic substitution these materials can diversify into, for example, the silicoaluminophosphate (SAPO) family of heterogeneous acid catalysts. Research into the methods by which these substitutions occur, as discoveries can lead to refined control over material property and function. SAPO-5 was chosen as model system of study.27Al,29Si and31P solid state NMR and PXRD were used as the primary methods of investigation. The SAPO-5 study determined that the dry gel conversion (DGC) methods of steam assisted conversion (SAC) and vapor phase transport (VPT) follow similar reaction pathways. After an initial difference caused by the lack of organic structure directing agent in the gel for the VPT method, crystallization is similar between methods, and silicon incorporation results in two populations of silicon sites. One represents isolated Si(OAl)4species well incorporated into the framework, while the other represents silica islands within the framework. The initial core of the nuclei is AlPO4in nature and the Si is gradually incorporated into the lattice as the crystals grow. The vapor phase silicon uptake (VPSU) method provides a contrast to this data, inducing nucleation that occurs concurrently with Si incorporation and producing only isolated Si(OAl)4species.