Enhancement of Catalyst Performance in the Direct Propene Epoxidation: A Study into Gold-Titanium Synergy

Enhanced productivity toward propene oxide in the direct propene epoxidation with hydrogen and oxygen over gold nanoparticles supported on titanium‐grafted silica was achieved by adjusting the gold–titanium synergy. Highly isolated titanium sites were obtained by lowering the titanium loading grafted on silica. The tetrahedrally coordinated titanium sites were found to be favorable for attaining small gold nanoparticles and thus a high dispersion of gold. The improved productivity of propene oxide can be attributed to the increased amount of the interfacial AuTi sites. The active hydroperoxy intermediate is competitively consumed by epoxidation and hydrogenation at the AuTi interface. A higher propene concentration is favorable for a lower water formation rate and a higher formation rate of propene oxide. Propene hydrogenation, if occurring, can be switched off by a small amount of carbon monoxide. A productive attraction: Highly active catalysts in the direct epoxidation of propene were achieved by adjusting the site synergy between gold and titanium in a catalyst system made of gold nanoparticles on Ti‐grafted silica as the support. High dispersion of gold close to the tetracoordinated Ti provides sufficient AuTi interface leading to the high activity of these catalysts (see picture).