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Seed-Assisted Zeolite Synthesis: The Impact of Seeding Conditions and Interzeolite Transformations on Crystal Structure and Morphology
Microporous and Mesoporous Materials ( IF 5.2 ) Pub Date : 2020-03-16 , DOI: 10.1016/j.micromeso.2020.110174
Rishabh Jain , Jeffrey D. Rimer

Seed-assisted approaches in zeolite synthesis differ from classical processes in that the seeds tend to dissolve, giving rise to an unknown memory of the parent crystal structure that facilitates the nucleation of the daughter. It has been hypothesized in literature that a shared structural feature, such as a composite building unit, between the parent and the crystals produced from a non-seeded growth solution results in identical parent-daughter framework types. In this study, our findings reveal that this scenario is true in select cases, but often the initial structure formed in seeded syntheses is metastable, resulting in interzeolite transformation(s) with prolonged hydrothermal treatment. In general, the trajectory tends to favor a final structure identical to that obtained by non-seeded growth under identical synthesis conditions. Here, we explore how seed-assisted syntheses impact zeolite properties such as size, morphology, structure, and defects. We observe that the molar composition of the growth mixture and the properties of the seed crystals play a significant role in controlling the kinetics of nucleation and the trajectory of interzeolite transformations. Furthermore, we observe that seeds offer unique routes to achieve small crystal sizes and distinct morphologies in comparison to many conventional syntheses. Advantages of seeding include shorter synthesis time and the ability to reduce or eliminate the need for organic structure-directing agents, thereby providing a facile and efficient route to design zeolites for various industrial applications. The fundamental mechanisms underlying zeolite seed-assisted crystallization are complex and elusive; however, our study provides new insight into these processes and highlights the important role of kinetics in governing parent-daughter (or seed-product) relationships.



中文翻译:

种子辅助沸石合成:接种条件和沸石转变对晶体结构和形态的影响

沸石合成中的晶种辅助方法与经典方法不同,在于晶种易于溶解,导致对母体晶体结构的未知记忆,从而促进了子核的形核。在文献中已经假设,在母体和由非种子生长溶液产生的晶体之间共享结构特征(例如复合建筑单元)会导致相同的母女框架类型。在这项研究中,我们的发现表明,在某些情况下这种情况是正确的,但种子合成中形成的初始结构通常是亚稳态的,从而导致沸石与水合物的长时间热处理而发生转变。通常,轨迹倾向于倾向于与在相同合成条件下通过非种子生长获得的结构相同的最终结构。这里,我们探索了种子辅助合成如何影响沸石的性质,例如大小,形态,结构和缺陷。我们观察到,生长混合物的摩尔组成和籽晶的性质在控制成核动力学和沸石间转变的轨迹中起着重要作用。此外,我们观察到,与许多常规合成方法相比,种子提供了实现较小晶体尺寸和不同形态的独特途径。播种的优点包括较短的合成时间以及减少或消除对有机结构导向剂的需求的能力,从而为设计用于各种工业应用的沸石提供了简便而有效的途径。沸石晶种辅助结晶的基本机理是复杂而难以捉摸的。然而,

更新日期:2020-03-16
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