Continuous-Flow Alkene Metathesis: The Model Reaction of 1-Octene Catalyzed by Re2O7/alfa-Al2O3 with Supercritical CO2 as a Carrier

In the presence of Re2O7 supported on γ-Al2O3, the self-metathesis of 1-octene was conveniently carried out under continuous-flow (CF) conditions using supercritical CO2 (scCO2) as a carrier. This investigation allowed optimization of reaction parameters, the best values of which were found to be 100 °C and 90 bar, operating at flow rates of 0.05 and 1 mL min−1 for 1-octene and scCO2, respectively, the reaction proceeded with very good self-metathesis selectivity (>90%) and an average productivity of ∼0.24 mL tetradecene gRe −1 min−1 . Although the catalyst was completely deactivated after the first 100–150 min of reaction, it could be recycled for (at least) five subsequent reactions without any loss of performance. The results provided incontrovertible evidence that for the investigated reaction, scCO2was a superior carrier with respect to conventional liquids, such as toluene or n-hexane.