Synthesis of Zeolites via Interzeolite Transformations without Organic Structure-Directing Agents
Synthesis of Zeolites via Interzeolite Transformations without Organic Structure-Directing Agents
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DOI：
10.1021/cm504510f
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发表时间：
2015-03-24
影响因子：
8.6
通讯作者：
Iglesia, Enrique
中科院分区：
文献类型：
--
作者：
Goel, Sarika;Zones, Stacey I.;Iglesia, Enrique
我们报告的合成协议和指导原则的启发，通过沸石间的转换，避免直接干预的有机结构导向剂的结晶微孔固体的合成的机械考虑。具体实施这些方案以从FAU（八面沸石）或ZSM（β）母体材料合成高二氧化硅MFI（ZSM-5）、CHA（菱沸石）、STF（SSZ-35）和MTW（ZSM-12）沸石。当它们导致具有更高骨架密度的子结构时，这些转化成功，并且它们的成核和生长通过种子或母体和目标结构共有的结构构建单元的存在而变得可能，在后一种情况下，通过选择适当的合成条件导致自发转化。这些协议允许高硅框架的合成，而无需使用有机模板，否则需要。试剂中的NaOH/SiO2比率和Al含量用于加强母体沸石域内的溶胀和局部重构与来自目标结构的种子的碎片或构建单元的破坏之间的同步。晶种介导的相互转化保持了母体晶体的习性和体积，因为在母体结构域的外部区域处的目标结构的初期成核。这些转化的假晶性质需要子沸石晶体内的中孔的同时成核，因为它们的骨架密度大于母体沸石的骨架密度。所描述的方法和证据第一次表明，可以在没有最初用于发现它们的有机模板的情况下制备广泛的富含二氧化硅的沸石，从而更有用地作为催化剂。
We report synthetic protocols and guiding principles inspired by mechanistic considerations for the synthesis of crystalline microporous solids via interzeolite transformations that avoid direct intervention by organic structure-directing agents. These protocols are specifically implemented to synthesize high-silica MFI (ZSM-5), CHA (chabazite), STF (SSZ-35), and MTW (ZSM-12) zeolites from FAU (faujasite) or BEA (beta) parent materials. These transformations succeed when they lead to daughter structures with higher framework densities, and their nucleation and growth become possible by the presence of seeds or of structural building units common to the parent and target structures, leading, in the latter case, to spontaneous transformations by choosing appropriate synthesis conditions. These protocols allow the synthesis of high-silica frameworks without the use of organic templates otherwise required. The NaOH/SiO2 ratio and Al content in reagents are used to enforce synchronization between the swelling and local restructuring within parent zeolite domains with the spoiling of fragments or building units from seeds of the target structure. Seed-mediated interconversions preserve the habit and volume of the parent crystals because of the incipient nucleation of the target structure at the outer regions of the parent domains. The pseudomorphic nature of these transformations requires the concurrent nucleation of mesopores within daughter zeolite crystals because their framework density is larger than that for the parent zeolites. The approach and evidence described shows, for the first time, that a broad range of zeolites rich in silica, and thus more useful as catalysts, can be made without the organic templates originally used to discover them.