复旦大学朱卡克团队通过结构导向剂交换诱导再结晶制备具有还原b轴的组装MFI纳米晶。相关研究成果于2021年4月12日发表在《德国应用化学》。

控制沸石材料的晶粒尺寸和形状是提高其传质性能和催化性能的有效途径。

该文中，研究人员报告了一种单步无钠无气孔MFI分层结构的结晶，该结构由排列的纳米晶体组成，b轴厚度（5-23 nm）减小，Si/Al比（35-120）可调节，采用常用的四丙基氢氧化铵（TPAOH）和四丁基氢氧化铵（TBAOH）作为结构导向剂（SDAs）。由SDA和随后的SDA交换诱导溶解-再结晶驱动的均匀形核是形成这种结构的原因。在二甲醚转化为烯烃（DTO）过程中，二甲醚的结构和扩散性能的提高是丙烯选择性和催化剂寿命显著延长的原因。

该方案可扩展到通过结晶过程控制合理合成其它分级分子筛。

附：英文原文

Title: Generating assembled MFI nanocrystals with reduced b‐axis through structure‐directing agent exchange induced recrystallization

Author: Xiaoling Zhao, Shu Zeng, Xueliang Zhang, Quanzheng Deng, Xiujie Li, Wenguang Yu, Kake Zhu, Shutao Xu, Jichang Liu, Lu Han

Issue&Volume: 2021-04-12

Abstract: Controlling crystal size and shape of zeolitic materials is an effective way to promote their mass transport and catalytic properties.  Herein, we report a single step, Na  +  ‐ and porogen‐ free crystallization of  MFI  hierarchical architecture made up of aligned nanocrystals with reduced  b  ‐axis thickness (5‐23 nm) and adjustable Si/Al ratios between 35 to 120, employing the commonly used tetrapropylammonium hydroxide (TPAOH) and tetrabutylammonium hydroxide (TBAOH) as structure‐directing agents (SDAs). Homogeneous nucleation driven by both SDAs and subsequent SDA‐exchange induced dissolution‐recrystallization are responsible for the formation of such structure. The enhanced textural and diffusion properties account for a notable  exaggeration of propene selectivity and catalyst lifetime in dimethyl in dimethyl ether‐to‐olefins (DTO) conversion.  This protocol is extendable to the rational synthesis of other hierarchical zeolites through crystallization process control.

DOI: 10.1002/anie.202017031

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202017031