Preferential oxidation of CO in H₂ stream on Au/CeO₂-TiO₂ catalysts

A series of Au catalysts supported on CeO₂-TiO₂ with various CeO₂ contents were prepared. CeO₂-TiO₂ was prepared by incipient-wetness impregnation with aqueous solution of Ce(NO₃)₃ on TiO₂. Gold catalysts were prepared by deposition-precipitation method at pH 7 and 65 °C. The catalysts were characterized by XRD, TEM and XPS. The preferential oxidation of CO in hydrogen stream was carried out in a fixed bed reactor. The catalyst mainly had metallic gold species and small amount of oxidic Au species. The average gold particle size was 2.5 nm. Adding suitable amount of CeO₂ on Au/TiO₂ catalyst could enhance CO oxidation and suppress H₂ oxidation at high reaction temperature (>50 °C). Additives such as La₂O₃, Co₃O₄ and CuO were added to Au/CeO₂-TiO₂ catalyst and tested for the preferential oxidation of CO in hydrogen stream. The addition of CuO on Au/CeO₂-TiO₂ catalyst increased the CO conversion and CO selectivity effectively. Au/CuO-CeO₂-TiO₂ with molar ratio of Cu:Ce:Ti = 0.5:1:9 demonstrated very high CO conversion when the temperature was higher than 65 °C and the CO selectivity also improved substantially. Thus the additive CuO along with the promoter and amorphous oxide ceria and titania not only enhances the electronic interaction, but also stabilizes the nanosize gold particles and thereby enhancing the catalytic activity for PROX reaction to a greater extent. Crown