Evolution of Zn Species on Zn/HZSM‐5 Catalyst under H₂ Pretreated and its Effect on Ethylene Aromatization

Abstract

Abstract Aromatization reaction is of importance in producing aromatics, accompanied by the generation of abundant H 2 , which may influence the reaction by interacting with the catalyst. In this work, Zn‐containing ZSM‐5 prepared by impregnation was treated in H 2 atmosphere at different temperatures, and the evolution in structure, acidity, and Zn species distribution were studied. The catalyst's performance in ethylene aromatization was also evaluated. The results show that the H 2 atmosphere enabled the reconstruction of ZnO microparticles and the reformation of Brønsted acid sites on Zn/HZSM‐5 below 200 °C. At an elevated temperature (300 °C), Zn + species were produced by the reduction of [ZnOZn] 2+ as confirmed by in‐situ Zn K ‐edge extended X‐ray absorption fine structure (EXAFS) study and density functional theory (DFT) calculation. After H 2 pretreatment at 300 °C, the increase in the amount of ZnOH + species increased the selectivity of Zn‐containing ZSM‐5 for aromatics from 62 % to 67 %.