The propylene oxidation reaction was investigated over model supported vanadia catalysts with combined operando Raman, IR, UV-Vis DRS and temperature programmed surface reaction (TPSR) spectroscopy in order to better understand the selective oxidation of propylene to oxygenates. The oxidation of propylene to acrolein was found to involve two surface VO₄ sites and proceeds via a combined Langmuir-Hinshelwood and Mars-van Krevelen surface reaction mechanisms. The selective oxidation of propylene to oxygenate requires the presence of gas phase molecular O₂ and the presence of surface V⁺⁵ sites. Additional insights about the participation of gas phase molecular O₂ and rate-determine-step (rds) in this reaction were obtained from transient isotopically labeled ¹⁸O₂ and C₃D₆ studies. C₃D₆ studies indicate that the C-H bond breaking is the rds of the reaction. ¹⁸O₂ study showed the presence of gas phase molecular O₂ help to remove the H atom after C-H bond breaking, only surface O from the catalysts can form acrolein. The most abundant surface reaction intermediate on the catalyst surface during propylene oxidation is the surface allyl (H₂CCHCH₂) intermediate. The elementary reaction steps and surface reaction kinetics involved in the selective oxidation of propylene over the model supported vanadia catalysts will also be discussed.

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