Propylene Epoxidation to Propylene Oxide Over RuO₂, CuO, TeO₂, and TiO₂ Supported on Modified Mesoporous Silicas.

Direct gas phase epoxidation of propylene to propylene oxide (PO) using O₂ is a challenging problem in catalysis research. Silica-supported ruthenium-copper-based catalysts have been recently reported to be promising for propylene epoxidation. In this work, mesoporous silica supports modified with RuO₂, CuO, and TeO₂ with and without TiO₂ were investigated for propylene epoxidation to PO. The prepared catalysts were divided into two groups. The first group consisted of mesoporous silica supports modified with RuO₂, CuO, and TeO₂, and the second group consisted of the same components as the first group but adding TiO₂. The prepared supports and catalysts were characterized using BET surface area analysis and other advanced instrument techniques. It was found that the catalyst made with RuO₂ and TeO₂ impregnated onto porous silica modified with CuO and TiO₂ (denoted as RuTe/CuTiSi) exhibited an excellent PO formation of 344 gPO h-1 kg-1cat, which was superior to that of the other prepared catalysts. Moreover, the addition of TiO₂ into the catalyst greatly improved the PO formation rate and the arrangement of active components in the catalyst and strongly influenced catalytic performance.