Insights on the seed selection criteria of SAPO-34 synthesis: structural units and their chemical microenvironment,Inorganic Chemistry Frontiers

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Insights on the seed selection criteria of SAPO-34 synthesis: structural units and their chemical microenvironment
Inorganic Chemistry Frontiers ( IF 6.1 ) Pub Date : 2023-05-22 , DOI: 10.1039/d3qi00646h
Xiaosi Zhang _{1,

2} , Miao Yang ₁ , Ye Wang _{1,

3} , Caiyi Lou _{1,

2} , Shutao Xu ₁ , Peng Tian ₁ , Zhongmin Liu _{1,

2}

Affiliation

Seed-assisted synthesis shows great potential to modify the properties of inorganic microporous materials and enhance synthetic efficiency. However, the understanding of the related mechanism is insufficient, especially in silicoaluminophosphate (SAPO) molecular sieve systems. In this work, the seed-assisted synthesis of SAPO-34, an important industrial methanol-to-olefins (MTO) catalyst with CHA topology, was investigated by using various seeds with different structures, compositions and morphologies. It reveals that both double 6-ring (d6r) units and complex Si environments are key features for a highly effective SAPO seed, which may provide small fragments containing complete or broken d6r units with Si–O–Al domains after the dissolution of seeds and thus derive the nucleation and crystallization of SAPO-34. Moreover, small crystal size and high Si content are positive factors for a qualified SAPO seed. Heteronuclear seeds, such as SAPO-18, SAPO-35 and SAPO-56, have been found to be effective for the synthesis of SAPO-34 with improved MTO catalytic performance. For SAPO materials without d6r units, their effect strongly depends on the growth solution and there is no preferential phase selectivity for SAPO-34. These findings could prompt the efficient synthesis and property control of SAPO molecular sieves.

中文翻译：

SAPO-34 合成种子选择标准的见解：结构单元及其化学微环境

种子辅助合成显示出改变无机微孔材料性能和提高合成效率的巨大潜力。然而，对相关机制的了解还不够，尤其是在硅铝磷酸盐 (SAPO) 分子筛系统中。在这项工作中，通过使用具有不同结构、组成和形态的各种种子，研究了 SAPO-34 的种子辅助合成， SAPO-34 是一种重要的具有CHA拓扑结构的工业甲醇制烯烃 (MTO) 催化剂。它揭示了双 6 环 ( d6r ) 单元和复杂的 Si 环境是高效 SAPO 种子的关键特征，它可能提供包含完整或损坏的d6r的小片段晶种溶解后具有 Si-O-Al 域的单元，从而得到 SAPO-34 的成核和结晶。此外，晶体尺寸小和Si含量高是获得合格SAPO晶种的积极因素。已发现异核种子，如 SAPO-18、SAPO-35 和 SAPO-56，可有效合成具有改进的 MTO 催化性能的 SAPO-34。对于没有d6r单元的 SAPO 材料，它们的效果在很大程度上取决于生长溶液，并且 SAPO-34 没有优先相选择性。这些发现可以促进 SAPO 分子筛的高效合成和性能控制。

更新日期：2023-05-22

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