Constructing surface ZnOH+-enriched Zn/ZSM-5 via tailoring acid sites for efficient ethylene aromatization

Abstract

Bifunctional Zn-modified HZSM-5 catalysts demonstrate excellent catalytic performance in ethylene aromatization. However, they often undergo rapid deactivation owing to the loss of zinc species. Here, we show that the activity of surface zinc species in Zn/ZSM-5 for ethylene aromatization can be enhanced by fine-tuning the synthesis parameters during the preparation of Zn-modified HZSM-5. Specifically, the Zn/ZSM-5 catalyst prepared under weakly acidic conditions exhibited superior anti-carbon deposition and anti-Zn loss properties compared to that prepared under alkaline conditions. We suggest that the reactivity of surface zinc species for ethylene aromatization was enhanced because of the formation of a hexacoordinated ZnOH⁺ species structure, which serves as the catalytic active center to facilitate dehydrogenation, thereby exhibiting a positive correlation with the catalyst's aromatization performance.