Mechanistic Insight into the Promotional Effect of CO2 on Propane Aromatization over Zn/ZSM-5

ZSM-5 zeolite modified by zinc is a promising catalyst for light alkane aromatization. CO2-assisted oxidative dehydrogenation and aromatization of propane can be achieved over Zn/ZSM-5, but the aromatization pathways and the role of CO2 remain to be clarified. With density functional theory calculations, this work investigates the reaction networks and key steps in propane aromatization over Zn/ZSM-5, the promotional role of CO2 in the consumption of H2 and the removal of carbon deposits, as well as the rate-limiting steps in the conversion of propane to aromatics. The calculation results demonstrate that Zn-Lewis acid sites play a vital role in propane dehydrogenation, while the subsequent propene aromatization proceeds under the synergetic action of both Bronsted and Zn-Lewis acid sites. Due to the high barrier step of CO2 activation involved in the reverse Boudouard reaction over Zn/ZSM-5, we identify that introducing a second metal component such as Pt or Cu into Zn/ZSM-5 can promote the removal of carbon deposits, thus leading to the enhanced catalyst stability and more active sites for aromatization.

Automated summary

Using density functional theory calculations, this study investigates the reaction networks and key steps in propane aromatization over Zn/ZSM-5 catalyst. The results show that Zn-Lewis acid sites play a crucial role in propane dehydrogenation, while propene aromatization proceeds under the combined action of Bronsted and Zn-Lewis acid sites. Moreover, introducing a second metal component can promote the removal of carbon deposits, leading to enhanced catalyst stability and more active sites for aromatization.