Kinetic study of propene oxide and water formation in hydro-epoxidation of propene on Au/Ti–SiO2 catalyst

• A kinetic study was performed on Au/TiSiO2 for the direct epoxidation of propene.
• A mechanism was proposed for the combined formation of propene oxide and water.
• The mechanism assumes two types of Au sites and HOOH as the active intermediate.
• A kinetic model was derived based on these fundamental surface reactions.
• The model could successfully describe the kinetic observations for both the products.

A highly stable and active, Au/TiSiO2 catalyst was used to conduct an extensive kinetic study for the direct epoxidation of propene using hydrogen and oxygen in the non-explosive regime, with an aim to study the combined formation of propene oxide and water. A reaction mechanism was proposed which assumes that there are two types of Au sites: isolated, which forms only water and the ones in the vicinity of Ti which forms propene oxide as well as water. The active intermediate on both was assumed to be the hydro peroxide species, as widely accepted. Based on fundamental reaction steps obtained from this mechanism, rate equations were derived and fitted with the experimental observations. The kinetic model was found to describe well the simultaneous formation of propene oxide and water, thus emphasizing on the importance of Au–Ti synergy to obtain catalysts with higher activity and H2 utilization ability.

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