Au was deposited on ultrastable Y (USY) zeolites using an ion-exchange method. Up to 5.5 wt% Au was introduced into the NH 4 -form of USY zeolites. In contrast, deposition of Au hardly took place on the H-and Na-forms of Y-type zeolites, NH 4 -forms of mordenite, and ZSM-5. Treatment of the Au-loaded USY zeolite in a H 2 atmosphere, afforded Au 0 nanoparticles. These particles were thermally stable even at 973 K, where their mean particle diameter was 3.7 nm. In contrast, highly aggregated Au particles were observed after thermal treatment at temperatures lower than 523 K, followed by storage in air for a month. The resulting particle sizes were in good correlation with the IR band intensity of the adsorbed CO and the catalytic activity of Au in the aerobic oxidation of benzyl alcohol. The Au nanoparticles showed highest activity when the Au/USY zeolite was thermally treated at 673-973 K. A negligible deactivation was observed after repeating the reaction at least 12 times. In the case of Au/TiO 2 catalyst prepared by the deposition-precipitation method, the highest activity was observed at 573 K, which was lower than the temperature used for the Au/USY zeolites. This study demonstrated the potential use of the NH 4 -form of USY zeolites for supporting Au. OPEN ACCESSCatalysts 2013, 3 600

Gold was deposited on ultrastable Y (USY) zeolite using a newly developed method: just mixing an aqueous solution of HAuCl 4 and zeolite at 353 K in which the NH 4 + cation reacted with the Cl − in HAuCl 4 . Treatment of the Au-loaded USY zeolite in the atmosphere of hydrogen resulted in the formation of Au 0 nanoclusters with 1.8 nm diameter at 773 K. The size of Au particle was dependent on the type of zeolite support, composition of gas atmosphere, and temperature of calcination, which was correlated with catalytic performance. This study demonstrated the potential use of zeolites with strong Brønsted acid character as gold supports.

Structural changes in the gold particles of Au-loaded ultrastable Y (USY) zeolite were analyzed by X-ray absorption fine structure, X-ray diffraction, and transmission electron microscopy. Au particles undergo spontaneous dispersion on the USY support under H2 atmosphere at a temperature of 773 K to give Au particles with an average diameter of 1.8 nm and narrow size distribution.