REDUCTION OF NITRIC-OXIDE BY CARBON-MONOXIDE OVER ZIRCONIA-SUPPORTED METAL-OXIDE CATALYSTS

Novel supported metal oxide catalysts were used for NO-CO reaction and their catalytic properties were studied. It was found that 3-5 wt% Fe/ZrO2 shows a higher activity for the reaction, no decay in activity at 250-350-degrees-C, and high resistance against thermal treatment. The turnover frequency of iron atom for the reaction showed a maximum at a 1 wt% Fe loading. 1 wt% Cu/ZrO2 catalyst showed a high activity for the NO reduction at 150-200-degrees-C and a high selectivity to N2 production. Deactivation of active copper species, however, was observed during the reaction. Compared with the catalytic behavior of CO oxidation over these catalysts, it is estimated that the NO-CO reaction over the Fe and Cu/ZrO2 catalysts proceeds via redox mechanisms. It was found that at a low temperature 2wt% Fe-0.5wt% Cu/ZrO2 composite catalyst shows a considerably higher activity for the reduction of NO to N2 than the sum of the activities of the corresponding Fe/ZrO2 and Cu/ZrO2 catalysts. The composite catalyst was also found to show a high selectivity to N2 and high stability toward activity decay.