Unraveling the Mechanism of Ethane Oxidative Dehydrogenation and the Important Role of Co2 Over Pt-Zn/Zsm-5 Catalysts

Abstract

This work studies the reaction mechanism and the role of CO2 in ethane dehydrogenation to ethene over two types of Pt-Zn/ZSM-5 catalysts. The calculation results demonstrate that the Pt-Zn sites have different roles, and Zn6Pt1/ZSM-5 is more active than Pt3Zn1/ZSM-5 due to more efficient Pt-Zn sites for dehydrogenation with the assistance of framework O of ZSM-5. CO2 reacts with H- species generated from ethane dehydrogenation and creates new and facile H-consuming routes, thus promoting the reaction. The positive effect of CO2 is more significant over Zn6Pt1/ZSM-5 than Pt3Zn1/ZSM-5 owing to the largely reduced barrier of rate-limiting step. Zn6Pt1/ZSM-5 greatly suppresses the competitive side reaction of CO2 with ethyl species, thus becoming a promising catalyst for ethene generation. This work deepens the mechanistic understanding of CO2-assisted dehydrogenation of light alkanes over Pt-Zn/ZSM-5 catalysts and unravels the important role of CO2, providing a useful reference for future catalyst design.

Keywords: Ethane dehydrogenation, Role of CO2, Pt-Zn/ZSM-5, Active sites, Reaction mechanism, Density Functional Theory