Design of a novel bifunctional catalyst IrFe/Al2O3 for preferential CO oxidation

In this study, a novel bifunctional catalyst IrFe/Al2O3, which is very active and selective for preferential oxidation of CO under H2-rich atmosphere, has been developed. When the molar ratio of Fe/Ir was 5/1, the IrFe/Al2O3 catalyst performed best, with CO conversion of 68% and oxygen selectivity towards CO2 formation of 86.8% attained at 100 °C. It has also been found that the impregnation sequence of Ir and Fe species on the Al2O3 support had a remarkable effect on the catalytic performance; the activity decreased following the order of IrFe/Al2O3 > co-IrFe/Al2O3 > FeIr/Al2O3. The three catalysts were characterized by XRD, H2-TPR, FT-IR and microcalorimetry. The results demonstrated that when Ir was supported on the pre-formed Fe/Al2O3, the resulting structure (IrFe/Al2O3) allowed more metallic Ir sites exposed on the surface and accessible for CO adsorption, while did not interfere with the O2 activation on the FeOx species. Thus, a bifunctional catalytic mechanism has been proposed where CO adsorbed on Ir sites and O2 adsorbed on FeOx sites; the reaction may take place at the interface of Ir and FeOx or via a spill-over process.