Catalytic Activity and Reaction Mechanism of Ru-Modified Ce0.7Zr0.3Ox Catalysts for Selective Catalytic Oxidation of Ammonia

To solve the problem of the poor low-temperature NH 3 selective catalytic oxidation (NH 3 –SCO) performance of CeZrO x catalysts, a series of Ru/CeZrO x catalysts with various Ru mass ratios were prepared via the impregnation–precipitation method. The introduction of Ru could significantly improve the low-temperature catalytic performance of CeZrO x catalysts from activity test results. Among prepared catalysts, the catalyst with a Ru mass ratio of 0.5 wt % and a Ce/Zr molar ratio of 7:3 (denoted as Ru 0.5 /CZO) was considered to have an excellent NH 3 –SCO performance; NH 3 conversion reached 100 and 91.2% N 2 selectivity at 237 °C. Physicochemical properties of Ru 0.5 /CZO and CZO catalysts were compared through a series of characterization tests to investigate the relationship between the introduction of Ru and the NH 3 –SCO performance. H 2 -TPR results revealed an interaction between the Ru and Ce species. The introduction of Ru significantly shifted the reduction peak toward the lower-temperature direction, enhancing the low-temperature redox performance of the CZO catalyst. NH 3 -TPD results indicated that Ru 0.5 /CZO catalysts had abundant acid sites on its surface, facilitating NH 3 adsorption and oxidation. In situ DRIFTS characterization results indicated that the reaction mechanism of the Ru 0.5 /CZO catalyst might be both internal-selective catalytic reduction (i-SCR) and imine (−NH) mechanisms.