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

Abstract

AbstractAromatization reaction is of importance in producing aromatics, accompanied by the generation of abundant H2, which may influence the reaction by interacting with the catalyst. In this work, Zn‐containing ZSM‐5 prepared by impregnation was treated in H2 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 H2 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 H2 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 %.