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Fabrication of Twin-Free Nanoslab ZSM-5 Zeolite with b-Axis Orientation for Super MTP Catalyst
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2022-07-11 , DOI: 10.1021/acssuschemeng.2c01813
Yu Sun 1 , Shiwei Cao 1 , Jie Wang 1 , He Tang 1 , Zhengkang Yang 1 , Tong Ma 1, 2 , Yanjun Gong 1 , Guang Mo 3 , Zhihong Li 3
Affiliation  

ZSM-5 zeolite with well-matched acidity and diffusivity is of significance for the improvement of acid catalytic performance. This study reports a novel synthesis for the twin-free ZSM-5 single crystal with nanoscaled b-axis orientation and its super performance in methanol to propylene (MTP) reaction. The synergistic effect of ZSM-5 nanosheet seed and n-butylamine template, the target ZSM-5 zeolite was achieved at a short crystallization time of 3.0 h. The as-synthesized ZSM-5 zeolite exposes open and high proportion of straight channels and features an inverse Al zoned distribution, which largely improves the intrinsic molecular diffusion and inhibits coke formation at the external surface. Finally, the optimal nanoslab ZSM-5 zeolite performs high MTP performance, i.e., the selectivity to propylene up to 50%, light olefins more than 80%, along with a very long catalytic life of 297 h at WHSV of 6 h–1. The role of the nanosheet seed in the crystallization process was studied by examining the structure evolution of the sol species by SAXS, XRD, SEM, TEM, Raman, FT-IR, etc. Results show that addition of ZSM-5 nanosheet seed can avoid secondary nucleation on the surface of a crystallizing zeolite and proves a quasi-solid-phase crystallization mechanism. Thus, the crystallization process belongs to a classical synthesis route, because the growth structure units are the smaller sized particle according to SAXS analysis.

中文翻译:

用于超级 MTP 催化剂的具有 b 轴取向的双自由 Nanoslab ZSM-5 沸石的制备

ZSM-5分子筛具有良好匹配的酸度和扩散性,对提高酸催化性能具有重要意义。本研究报告了一种具有纳米级b轴取向的无孪晶 ZSM-5 单晶的新合成方法及其在甲醇制丙烯 (MTP) 反应中的超强性能。ZSM-5纳米片种子和n的协同作用-丁胺模板,目标 ZSM-5 沸石在 3.0 小时的短结晶时间内实现。合成后的 ZSM-5 沸石暴露出开放且高比例的直通道,并具有反向 Al 区域分布,这大大改善了本征分子扩散并抑制了外表面的焦炭形成。最后,优化的纳米板 ZSM-5 沸石具有高 MTP 性能,即对丙烯的选择性高达 50%,对轻质烯烃的选择性超过 80%,并且在 6 h -1的 WHSV 下具有 297 h 的非常长的催化寿命。通过 SAXS、XRD、SEM、TEM、Raman、FT-IR等检测溶胶物质的结构演化,研究了纳米片晶种在结晶过程中的作用。结果表明,ZSM-5纳米片晶种的加入可以避免结晶沸石表面二次成核,证明了准固相结晶机制。因此,结晶过程属于经典合成路线,因为根据 SAXS 分析,生长结构单元是较小尺寸的颗粒。
更新日期:2022-07-11
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