Preferential oxidation of CO under excess H2H2 conditions over iridium catalysts

Iridium catalysts have been evaluated for the preferential CO oxidation under excess H2H2 conditions (PROX). The effects of various parameters including preparation methods, different oxides as supports, pretreatment process, content of Ir as well as reacting gas compositions on the catalytic performances were investigated. The results showed that both homogeneous deposition–precipitation (HDP) and deposition–precipitation (DP) methods could yield highly active Ir/CeO2Ir/CeO2 catalysts, attributed to their satisfactory elimination of chlorines. Iridium was also deposited on various oxide supports (CeO2CeO2, TiO2TiO2, Al2O3Al2O3 and MgO) by HDP method and only the Ir/CeO2Ir/CeO2 catalyst exhibited excellent performance in PROX process. Reductive pretreatment of the Ir/CeO2Ir/CeO2 (HDP) was found to be essential for obtaining the high activity. The best catalytic performance was obtained for the sample containing 1.60 wt% iridium. The presence of water in the feed had a negligible influence on the total activity for CO2CO2 formation; however, the presence of CO2CO2 negatively affected the catalytic performance of the Ir/CeO2Ir/CeO2 (HDP). Additionally, the good stability of the Ir/CeO2Ir/CeO2 catalyst makes it a promising candidate for PROX process.