The Roleof CO₂ in Oxidative Propane Dehydrogenationover Ga₂O₃/SiO₂ Catalysts

Abstract

Due to the substantial industrial significance of propylene and the development of shale gas, there is growing interest in propane dehydrogenation (PDH) technology for producing propylene. Gallium-based catalysts have significant potential in PDH technology due to their high activity and low carbon deposition. Additionally, CO₂ could reduce carbon deposition and promote reaction equilibrium, thereby enhancing the performance of the catalyst. To investigate the role of CO₂ in oxidative propane dehydrogenation, the Ga₂O₃/SiO₂ catalyst was synthesized by incipient wetness impregnation in this study. The activation energy for propane dehydrogenation with and without CO₂ was determined between 773 and 923 K, and the reaction orders were determined by varying the partial pressures of CO₂ and propane. The activation energies for both reactions were observed to be about 100 kJ·mol^–1, with a reaction order of 1 to 0 for propane and 0 for CO₂, ruling out competitive adsorption of CO₂ and propane on the catalyst. To clarify the reaction mechanism, a relatively simple model system was constructed to systematically and thoroughly investigate the role of CO₂ in the propane dehydrogenation process catalyzed by gallium oxide. The results suggest that CO₂ does not participate in the β-H elimination of propane or the reoxidation of gallium oxide, but instead, CO₂ enhances the PDH performance through coupling with the RWGS reaction.