Identification of the synergistic promotion of P and CO2 on propane dehydrogenation and aromatization over the Zn/P-ZSM-5 catalyst

This study performed DFT calculations to provide fundamental insights into the reaction mechanism of propane dehydrogenation and aromatization over Zn/P-ZSM-5 and elucidated the important roles of CO₂ and P in enhancing the reaction performance and catalyst stability. The rate-limiting steps for propane dehydrogenation and propene aromatization in the optimal energy pathways were identified, with energy barriers of 1.60 and 1.44 eV, respectively. The presence of CO₂ introduced new and more facile dehydrogenation routes, thereby lowering the barriers of the rate-limiting steps and facilitating the reaction. Besides, CO₂ could consume carbon deposits via the reverse Boudouard reaction, which is beneficial for extending the catalyst life. The addition of P to Zn/ZSM-5 improved the stability of active sites by strengthening their resistance towards water, enhanced the interactions between the catalyst and reactants, and induced electron transfer and charge redistribution at Zn-Lewis sites by creating new non-framework O sites, thus altering the oxidation state and acidity of the Zn-Lewis sites. The synergistic promotional effects of CO₂ and P offer a promising strategy for designing efficient zeolite-based catalysts for the dehydrogenation and aromatization of light alkanes.