Structure Evolution of Zn Species on Fresh, Deactivated, and Regenerated Zn/ZSM-5 Catalysts in Ethylene Aromatization,ACS Catalysis

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Structure Evolution of Zn Species on Fresh, Deactivated, and Regenerated Zn/ZSM-5 Catalysts in Ethylene Aromatization
ACS Catalysis ( IF 11.3 ) Pub Date : 2022-11-17 , DOI: 10.1021/acscatal.2c04074
Rui Geng _{1,

2} , Yacong Liu _{1,

2} , Yanxia Guo _{1,

2} , Pengfei Wang _{1,

2} , Mei Dong ₁ , Sen Wang ₁ , Jianguo Wang _{1,

2} , Zhangfeng Qin ₁ , Weibin Fan ₁

Affiliation

Zn-modified ZSM-5 catalysts were widely used in ethylene aromatization; however, the deactivation and regeneration behavior of these catalysts have not been fully understood. In this work, the structure evolution of Zn species on various x-Zn(y)/Z5 catalysts prepared by ion exchange, incipient wetness impregnation, and physical mixture in ethylene aromatization were systemically investigated. The results of X-ray diffraction, X-ray photoelectron spectroscopy, DR UV–vis, ²⁷Al/²⁹Si MAS NMR, EXAFS, and X-ray absorption near edge spectra with LCF analysis indicated that the generated coke species on spent Zn/ZSM-5 can not only cover the acid sites and block the pore channel but also lead to the transformation of active 6-fold coordinated ZnOH⁺ species into unactive 4-fold coordinated ZnO. After regeneration to eliminate these carbon deposits, the crystallinity, specific surface area, pore volume, and total acid content of regenerated Zn/ZSM-5 were fully recovered. More importantly, most of the ZnO clusters/crystals were converted into ZnOH⁺ species again. As a result, the regenerated Zn/ZSM-5 catalysts showed even higher aromatic selectivity than the fresh one in ethylene aromatization.

中文翻译：

乙烯芳构化中新鲜、失活和再生 Zn/ZSM-5 催化剂上锌物种的结构演变

锌改性ZSM-5催化剂广泛应用于乙烯芳构化；然而，这些催化剂的失活和再生行为尚未完全了解。在这项工作中，系统地研究了通过离子交换、初湿浸渍和物理混合制备的各种x -Zn( y )/Z5 催化剂在乙烯芳构化中 Zn 物种的结构演变。X射线衍射、X射线光电子能谱、DR UV-vis, ²⁷ Al/ ^29结果Si MAS NMR、EXAFS 和 X 射线吸收近边光谱以及 LCF 分析表明，在废 Zn/ZSM-5 上生成的焦炭物种不仅可以覆盖酸性位点并堵塞孔道，还可以导致活性转化6 重配位的 ZnOH ⁺物质转化为无活性的 4 重配位 ZnO。经过再生去除这些积碳后，再生后的Zn/ZSM-5的结晶度、比表面积、孔容和总酸含量均得到充分恢复。更重要的是，大部分 ZnO 团簇/晶体再次转化为 ZnOH ⁺物质。结果，再生的 Zn/ZSM-5 催化剂在乙烯芳构化中表现出比新鲜催化剂更高的芳烃选择性。

更新日期：2022-11-17

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