Olefin metathesis with mesoporous rhenium–silicium–aluminum mixed oxides obtained via a one-step non-hydrolytic sol–gel route

Mesoporous Re–Si–Al, Re–Al, and Re–Si mixed oxides were obtained via a one-step non-hydrolytic sol–gel route followed by calcination. The texture and surface properties of the resulting catalysts were characterized by a combination of EDX, XRD, N2-physisorption, XPS, ToF-SIMS, and NH3-TPD. The loss of rhenium during calcination, the texture and the acidity of the catalysts depended on their composition. Migration of rhenium toward the surface occurred during the calcination treatment, as evidenced by XPS and ToF-SIMS. After calcination, ToF-SIMS showed the presence of well-dispersed ReOx surface species. The influence of the composition of Re–Si–Al catalysts on their performances in the cross-metathesis of ethene and butene to propene was investigated. The specific activity of the Re–Si–Al catalysts was much higher than that of Re–Al catalysts, whereas the Re–Si sample was not active. The best Re–Si–Al catalysts displayed excellent specific activities (up to 45 mmol g−1 h−1) and apparent TOF values (98 × 10−3 s−1).

A one-step non-hydrolytic sol–gel route based on chloride precursors and diisopropyl ether leads in the absence of structure directing agents to mesoporous Re–Si–Al mixed oxide xerogels. Rhenium loss during calcination can be avoided, and highly dispersed ReOx species are stabilized at the surface, resulting in excellent olefin metathesis activity.Figure optionsDownload high-quality image (120 K)Download as PowerPoint slideHighlights
► A simple way to prepare rhenium–silicium–aluminum mixed oxide catalysts.
► Non-hydrolytic sol–gel method offers a good control on Si/Al ratio, Re loading, and texture.
► Re species migrate toward the surface upon calcination.
► Catalyst surface is covered mainly by dispersed rhenium species.
► Catalysts are highly active in the cross-metathesis of ethene and 2-butene to propene.