Formation Pathway of AEI Zeolites as a Basis for a Streamlined Synthesis,Chemistry of Materials

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Formation Pathway of AEI Zeolites as a Basis for a Streamlined Synthesis
Chemistry of Materials ( IF 7.2 ) Pub Date : 2019-12-05 , DOI: 10.1021/acs.chemmater.9b02227
Nao Tsunoji ₁ , Daigo Shimono ₁ , Kazuyoshi Tsuchiya ₁ , Masahiro Sadakane ₁ , Tsuneji Sano ₁

Affiliation

Zeolites are commercially used crystalline microporous materials. Understanding their crystallization mechanism and corresponding synthesis development is still of scientific and technological significance. Herein, we investigated the formation process of AEI zeolite using a combination of analysis methods, including X-ray diffractometry, nuclear magnetic resonance, and electrospray-ionization mass spectrometry, and developed a rational synthesis method without the use of a specific silica/alumina source (FAU zeolite). First, the synthesis condition was optimized by selecting a variety of synthesis components: FAU zeolites with different Al contents, colloidal silica, sodium aluminate, and three types of organic structure-directing agents (OSDAs). AEI zeolite preintroduced into the synthesis system (seed crystal) enabled its crystal growth from an easily available amorphous silica/alumina source. Stepwise gel preparation (SGP) through divided compositional control using an amorphous starting material effectively provided AEI zeolite in the presence of two types of OSDAs. A selected synthesis component (SGP with N,N-dimethyl-3,5-dimethylpiperidinium) formed AEI zeolite without even using AEI seed. Although the product contained a trace amount of impurity, it could be used as seed crystal for providing pure-phased AEI zeolite. Finally, from the merged synthetic and analytical results, we proposed that oligomeric aluminosilicate with a low dehydration degree contributes to AEI zeolite nucleation from an amorphous starting material. Furthermore, AEI zeolite catalyst with high activity and durability for emission-gas purification can be prepared by the SGP synthesis strategy. This comprehensive study would help rationally build zeolite synthesis and function design, particularly in a case that strongly depends on the starting material.

中文翻译：

AEI沸石的形成途径作为流线型合成的基础

沸石是商业上使用的结晶微孔材料。了解它们的结晶机理和相应的合成发展仍具有科学技术意义。本文中，我们使用X射线衍射法，核磁共振法和电喷雾电离质谱法等分析方法相结合的方法研究了AEI沸石的形成过程，并开发了不使用特定二氧化硅/氧化铝源的合理合成方法（FAU沸石）。首先，通过选择各种合成组分来优化合成条件：具有不同Al含量的FAU沸石，胶体二氧化硅，铝酸钠和三种类型的有机结构导向剂（OSDA）。预引入到合成系统（种子晶体）中的AEI沸石使它能够从容易获得的无定形二氧化硅/氧化铝源中生长出晶体。在两种类型的OSDA的存在下，通过使用无定形原料进行分组分控制，逐步制备凝胶（SGP）可有效提供AEI沸石。选定的合成成分（具有N，N-二甲基-3,5-二甲基哌啶）形成AEI沸石，甚至不使用AEI晶种。尽管产物中含有微量的杂质，但它可以用作提供纯相AEI沸石的晶种。最后，从合并的合成和分析结果中，我们提出低脱水度的低聚硅铝酸盐有助于从非晶态起始材料中形成AEI沸石核。此外，可以通过SGP合成策略制备用于废气净化的具有高活性和耐久性的AEI沸石催化剂。这项全面的研究将有助于合理地构建沸石的合成和功能设计，尤其是在强烈依赖原材料的情况下。

更新日期：2019-12-05

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