Unraveling the Propane to Propene Conversion over WOx/SiO2 Catalysts: A Combined DFT and Microkinetic Modeling Study

Although WOx/SiO2 systems are widely used as industrial catalysts for olefin metathesis, the use of this catalyst in alkane-to-alkene conversion is yet unknown. This work combines density functional theory calculations with microkinetic modeling to systematically explore propane to propene conversion over W(VI) dioxo species, both with and without catalyst reduction, along with W(VI) mono-oxo pathways. The mono-oxo W(VI) species is observed as the most promising catalytic site for propane dehydrogenation due to its greater reactivity in facilitating effective C–H activation with a lowest effective barrier of 2.76 eV at 823 K. Microkinetic analysis revealed that the initial C–H cleavage of propane is the rate-determining step for the dehydrogenation pathway over W(VI) mono-oxo species. In addition, microkinetic calculations predicted a high TOF on the order of 10-3 s-¹ for propane dehydrogenation over W(VI) mono-oxo species at the reported olefin metathesis catalyst activation temperature 700 ˚C (973 K). As the dioxo W(VI) species (A0) is believed to be the active site for propene metathesis, these DFT results strongly suggest that instead of using separate catalysts, a single WOx/SiO2 catalyst may be sufficient for converting propane into propene efficiently via high-temperature pretreatment of the catalyst with propane prior to propene metathesis at a lower temperature.