Epoxidation of propylene over gold catalysts supported on non-porous silica Original Research Article

Non-porous silica was used as a carrier of Au/Ti-SiO2 catalysts for the direct vapor-phase epoxidation of propylene in the copresence of H2 and O2, because the smooth surfaces were expected to facilitate the desorption of propylene oxide (PO). Their catalytic performances were inferior to those of Au/TS-1 and Au/Ti-MCM catalysts, however, an interesting feature was that propylene epoxidation over Au/Ti-SiO2 appreciably depended on calcination temperature of the Ti-SiO2 support. Higher calcination temperature benefits PO production at reaction temperatures above 100°C. IR and HRTEM analyses showed that the interaction between titanium oxides and silica was intensified to form more isolated TiO4 units with tetrahedral coordination on the surfaces of Ti-SiO2 supports with an increase in heat treatment temperature. These isolated TiO4 sites incorporated in silica surface layers are assumed to be an important structural factor for the selective deposition of Au particles and the selective PO formation.