Hydrogen production from ethanol over Ir/CeO2 catalysts : A comparative study of steam reforming, partial oxidation and oxidative steam reforming

Steam reforming, partial oxidation, and oxidative steam reforming of ethanol over Ir/CeO2 catalysts were studied to elucidate the reaction pathway and determine catalytic stability. Temperature-programmed desorption and surface reaction revealed that ethoxy species were immediately formed on ethanol adsorption at room temperature, and were mainly further oxidized to acetate and carbonate species that finally decomposed into CH4/CO and CO2, respectively. Under reaction conditions, acetaldehyde was the primary product below 673 K, which decomposed mainly to methane and carbon monoxide at higher temperatures, whereas methane reforming and the water-gas shift were the major reactions above 773 K. The Ir/CeO2 catalyst demonstrated rather high stability for the reactions at 823 and 923 K with no apparent deactivation for 60 h on stream; the mean size of Ir particles was stable at around 2-3 nm, but the ceria particles sintered significantly from 6-8 to 14-27 nm. CeO2 likely prevented the highly dispersed Ir particles from sintering and inhibited coke deposition through strong Ir-CeO2 interactions. [PUBLICATION ABSTRACT]