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Rh/gamma-Al2O3 and Rh-Au/gamma-Al2O3 catalysts were prepared by the ultrasound-assisted membrane reduction (UAMR) and the incipient wetness impregnation (IMP) methods. The properties of the catalysts for three-way catalytic model reactions (CO and C3H8 oxidation, CO + NO, and C3H6+NO+O-2) were investigated. The catalysts were characterized by inductively coupled plasma-optical emission spectrometry, H-2-O-2 titration, N-2 adsorption, and transmission electron microscopy. The metal dispersion of the Rh/gamma-Al2O3-UAMR and Rh-Au/gamma-Al2O3-UAMR catalysts was 45.3% and 40.1% with the metallic surface area of 199.6 and 133.0 m(2)/g, respectively, and the average metal particle size was smaller than 3 nm. Compared with Rh/gamma-Al2O3-IMP and Rh-Au/gamma-Al2O3-IMP, the Rh/gamma-Al2O3-UAMR and RhAu/gamma-Al2O3-UAMR catalysts possessed much higher catalytic activity for the model reactions. However, the activity of the Rh-Au/gamma-Al2O3- UAMR catalyst was higher than or similar to that of the Rh/gamma-Al2O3-IMP for the model reactions, indicating that the UAMR is a promising method for fabrication of three-way catalysts. The catalysts were deactivated to some extent by hydrothermal pretreatment at 1 000 degrees C.
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