Highly Efficient Activation, Regeneration, and Active Site Identification of Oxide-Based Olefin Metathesis Catalysts

Supported metal oxide based olefin metathesis catalysts are widely used in the chemical industry. In comparison to their organometallic catalyst cousins, the oxide catalysts have much lower activity due to the very small fraction of active sites. We report that a simple pretreatment of MoO3/SiO2 and WO3/SiO2 under an olefin-containing atmosphere at elevated temperatures leads to a 100–1000-fold increase in the low-temperature propylene metathesis activity. The performance of these catalysts is comparable with those of the well-defined organometallic catalysts. Unprecedentedly, the catalyst can be easily regenerated by inert gas purging at elevated temperatures. Furthermore, using UV resonance Raman spectroscopy and electron microscopy, we provide strong evidence that the active sites for MoO3/SiO2 are derived from monomeric Mo(═O)2 dioxo species.