Propene epoxidation with O2 and H2: Identification of the most active gold clusters

Gold was deposited on alkaline-treated TS-1 (TS-1-Na1) to prepare Au/TS-1-Na1(DP) by deposition–precipitation (DP) and Au/TS-1-Na1(SG) by solid grinding (SG). 129Xe NMR technique has detected that tiny Au clusters have been incorporated into the microporous channels of Au/TS-1-Na1(DP), while they were absent inside the microporous channels of Au/TS-1-Na1(SG). On the other hand, HAADF-STEM observation showed that the amount of Au clusters (1.0–2.0 nm) over the exterior surfaces was much larger in Au/TS-1-Na1(SG) than in Au/TS-1-Na1(DP). In propene epoxidation with O2 and H2, Au/TS-1-Na1(SG) exhibited much higher PO formation rate (127 gPO kgcat-1 h−1) than Au/TS-1-Na1(DP) (74 gPO kgcat-1 h−1), indicating that Au clusters with diameters of 1.0–2.0 nm are more active for PO synthesis than tiny Au clusters incorporated inside the microporous channels.

In propene epoxidation with O2 and H2, Au clusters (1.0–2.0 nm) on exterior surfaces of TS-1 treated with NaOH were more active than tiny Au clusters (<0.55 nm) inside micropores.Figure optionsDownload high-quality image (69 K)Download as PowerPoint slideResearch highlights
► Gold was deposited on alkaline treated TS-1.
► By deposition-precipitation Au was deposited as clusters (1.0−2.0 nm) on outer surfaces and tiny clusters (<0.55 nm) inside micropores.
► By solid grinding Au was deposited as clusters (1.0−2.0 nm) selectively on outer surfaces.
► SG sample was more active than DP sample.