Continuous-flow alkene metathesis: the model reaction of 1-octene catalyzed by Re2O7/γ-Al2O3 with supercritical CO2 as a carrier

In the presence of Re2O7 supported on gamma-Al2O3, the self-metathesis of 1-octene was conveniently carried out under continuous-flow (CF) conditions using supercritical CO2 (scCO(2)) as a carrier. This investigation allowed optimization of reaction parameters, the best values of which were found to be 100 degrees C and 90 bar, operating at flow rates of 0.05 and 1 mL min(-1) for 1-octene and scCO(2), respectively, the reaction proceeded with very good self-metathesis selectivity (>90%) and an average productivity of similar to 0.24 mL tetradecene g(Re)(-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, scCO(2)was a superior carrier with respect to conventional liquids, such as toluene or n-hexane.