Olefin Metathesis by Supported Metal Oxide Catalysts

The literature of olefin metathesis by heterogeneous supported catalysts, both industrial-type supported metal oxides (ReOx/Al2O3, ReOx/(SiO2-Al2O3), MoOx/SiO2, MoOx/Al2O3, MoOx/(SiO2-Al2O3), WOx/SiO2, and WOx/(SiO2-Al2O3)) and supported organometallic complexes, is comprehensively reviewed. The focus of this Review is supported metal oxide catalysts, but the well-defined supported organometallic catalyst literature is also covered because such model catalysts have the potential to bridge heterogeneous and homogeneous olefin metathesis catalysis. The recent world shortage of small olefin feedstocks has created renewed interest in olefin metathesis as a route to synthesizing small olefins and is reflected in the recent growth of the patent literature. Despite the extensive application of supported metal oxides in industry for metathesis of small and large olefins, the molecular structures and oxidation states of the catalytic active sites, surface reaction intermediates, and reaction mechanisms of this important catalytic reaction have still not been resolved. The absence of reported in situ and operando spectroscopic studies from the olefin metathesis catalysis literature has hampered progress in this area. It appears from this literature review that the topic of olefin metathesis by heterogeneous supported metal oxide catalysts is still a relatively undeveloped research area and is poised for significant progress in understanding of the fundamental molecular details of these important catalytic systems in the coming years.