Olefin metathesis is a versatile strategy for large-scale olefin interconversion, yet mechanistic details over industrial heterogeneous catalysts have remained ambiguous for decades. Here, from rigorous kinetic measurements, spectroscopic studies, and computational modeling of propylene metathesis over model and industrial WOx/SiO2 catalysts, we identify a hitherto unknown site renewal and decay cycle, mediated by proton transfers involving proximal Brønsted acidic OH groups, which operates concurrently with the classical Chauvin cycle. We show how this cycle can be manipulated using small quantities of promoter olefins to drastically increase steady-state propylene metathesis rates by up to 30-fold at 250oC with negligible promoter consumption. The increase in activity and considerable reduction of operating temperature requirements were also observed on MoOx/SiO2 catalysts, showing that this strategy is general and can address major roadblocks associated with industrial metathesis processes.
Universal promotion of heterogeneous olefin metathesis catalysts by controlling dynamic active site renewal
