La2O3-supported It catalyst was prepared by wetness impregnation method for the oxidative steam reforming of ethanol (OSRE). Fresh, reduced, and used catalysts were characterized by N-2 adsorption, H-2 chemisorption, XRD, FT-IR, TEM, and XPS. La2O3 would transform into hexagonal La2O2CO3 during OSRE, which suppress coking effectively. Reduced It metal can interplay with La2O2CO3 to form Ir-doped La2O2CO3. It dynamically forms and decomposes to release active It nanoparticles, thereby preventing the catalyst from sintering and affording high dispersion of Ir/La2O3 catalysts at elevated temperatures. By introducing ultrasonic-assisted impregnation method during the preparation of a catalyst, the surface It concentration was significantly improved, while the in situ dispersion effect inhibited It from sintering. The Ir/La2O3 catalyst prepared by the ultrasonic-assisted impregnation method is highly active and stable for the OSRE reaction, in which the It crystallite size was maintained at 3.2 nm after 100 h on stream at 650 degrees C and metal loading was high up to 9 wt%. (C) 2009 Elsevier Inc. All rights reserved.