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