Switching of reactions between hydrogenation and epoxidation of propene over Au/Ti-based oxides in the presence of H2 and O2

In a H2 and O2 mixture, the reaction of propene switches between hydrogenation and epoxidation over Au/Ti-based oxides. Reaction pathways are strongly dependent on the size of Au particles and on the presence of alkalis. The hydrogenation prevails over Au clusters smaller than 2.0 nm (in the absence of alkalis) and over Au nanoparticles larger than 5.0 nm. Alkali contamination can switch hydrogenation to epoxidation over Au clusters and promote epoxidation over Au nanoparticles with diameters of 2.0–5.0 nm. It was also confirmed that the hydrogenation of propene is enhanced by the addition of a small amount of O2. Switching of product by alkalis and enhancement of hydrogenation by oxygen are interpreted by parallel and competitive reaction pathways.

The size of Au particles and the presence of alkalis can switch hydrogenation and epoxidation of propene over Au/Ti-based oxides in a mixture with H2 and O2.Figure optionsDownload high-quality image (40 K)Download as PowerPoint slideHighlights
► Gold was deposited on three types of support with or without Ti.
► Propane was formed over Au particles (>5.0 nm) and Au clusters (<2.0 nm).
► Alkali contaminants can turn hydrogenation to epoxidation on Au clusters.
► Propane formation was enhanced by O2.
► Switching between hydrogenation and epoxidation of propene was discussed.