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). Xe-129 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 O-2 and H-2, Au/TS-1-Na1 (SG) exhibited much higher PO formation rate (127 gpo kg(cat)(-1) h(-1)) than Au/TS-1-Na1(DP) (74 gpo kg(cat)(-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. (C) 2010 Elsevier Inc. All rights reserved.