SAPO-34分子筛晶化过程中硅进入骨架的方式和机理

采用 Ｘ Ｒ Ｄ， Ｓ Ｅ Ｍ， Ｉ Ｒ 和 Ｎ Ｍ Ｒ 等手段考察了 Ｓ Ａ Ｐ Ｏ３４ 分子 筛的晶化过 程，深入研 究了晶化过程中硅进入 Ｓ Ａ Ｐ Ｏ３４ 晶格 骨架的方式和机理． 结果表明 ，在 Ｓ Ａ Ｐ Ｏ３４ 分子筛的整个晶化过程中没有 Ａｌ Ｐ Ｏ３４ 分 子筛晶相生成． 在 初始 凝 胶的 制备 过 程中， 模板 剂 的添 加和 混 合凝 胶的 老 化处 理对 Ｓ Ａ Ｐ Ｏ３４ 晶化过程的进行起着关键性的作用． 晶化前 期（ ＜ ２５ ｈ） ， 硅原子直接参与晶核的形成和晶粒的长大过程，形成 Ｓｉ（４ Ａｌ） 结构，此阶段基本上 可以排除硅取代磷机理的作用； 晶化后期（ ＞ ２５ ｈ） ，少量硅以取代方式进入分子 筛骨架形成 Ｓｉ（ ｎ Ａｌ）（ ｎ ＝ ０ ～４） 多种硅结构

METHOD AND MECHANISM OF Si INCORPORATION INTO LATTICE OF SAPO-34 MOLECULAR SIEVE

In the crystallization process of small pore molecular sieve SAPO 34, a series of samples were withdrawn by a self designed apparatus and characterized by XRD, SEM, IR and NMR techniques. The crystalloid, structure and composition changes of the liquid and solid samples during the crystallization process were investigated in order to get evidence for the method and mechanism of Si incorporation into SAPO 34 lattice. It was shown that there is no the crystalloid of AlPO 34 produced in the synthesis process. The template and the aging are crucial for the later crystallization of SAPO 34. According to IR and NMR studies, Si atoms directly take part in the formation of the crystal nucleus and the growth of the crystal grains other than substitute for P atoms in the initial stage (<2 5 h) of the crystallization. It can be ruled out that the replacement of the P atoms by Si for the increase of the Si content in the initial stage (<2 5 h) of the crystallization. It was found that the relative content of Si increased slightly with slight decrease of Al and P after 10 h. The increase of Si(4Al) and appearance of the Si(3Al), Si(2Al), Si(1Al) and Si(0Al) in the later stage suggested that the substitution of the Si atoms for the P and for the P Al pair took place.