Modification of photocatalytic center for photo-epoxidation of propylene by rubidium ion addition to V2O5/SiO2

The photo-oxidation of propylene with molecular oxygen was investigated over silica-supported vanadium oxide catalysts (VS) at 323 K. The addition of Rb ions to VS resulted in the great improvement of the formation rate of propylene oxide in the photo-oxidation of propylene (175 μmol g−1 h−1 for Rb-ion-modified VS, V2O5 loading 0.5 wt%, Rb/V = 1.5). The photocatalytic activity was significantly enhanced when the Rb/V ratio was greater than 1.0. UV-Vis diffuse reflectance and X-ray absorption spectra of a series of Rb-ion-modified VS catalysts indicated the presence of one-to-one interaction between a Rb ion and isolated VO4 tetrahedra over silica.