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 image h−1) than Au/TS-1-Na1(DP) (74 gPO image 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.