Efficient and stable oxidative steam reforming of ethanol for hydrogen production: Effect of in situ dispersion of Ir over Ir/La 2O 3

Abstract

La 2O 3-supported Ir 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. La 2O 3 would transform into hexagonal La 2O 2CO 3 during OSRE, which suppress coking effectively. Reduced Ir metal can interplay with La 2O 2CO 3 to form Ir-doped La 2O 2CO 3. It dynamically forms and decomposes to release active Ir nanoparticles, thereby preventing the catalyst from sintering and affording high dispersion of Ir/La 2O 3 catalysts at elevated temperatures. By introducing ultrasonic-assisted impregnation method during the preparation of a catalyst, the surface Ir concentration was significantly improved, while the in situ dispersion effect inhibited Ir from sintering. The Ir/La 2O 3 catalyst prepared by the ultrasonic-assisted impregnation method is highly active and stable for the OSRE reaction, in which the Ir crystallite size was maintained at 3.2 nm after 100 h on stream at 650 °C and metal loading was high up to 9 wt%.