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.