Rare earth oxide modified Cu-Mn compounds supported on TiO2 catalysts for low temperature selective catalytic oxidation of ammonia and in lean oxygen

Selective catalytic oxidation (SCO) of ammonia was carried out over Cu-Mn compounds catalysts modified with trivalent rare earth oxide Ce2O3 and La2O3 respectively. TiO2 was used as support and different ratio of O2 were tested in order to find an appropriate O2 concentration (vol.%), and the results showed that 1%O2 (vol.%) was propitious to SCO of ammonia. The effects of the two rare earth oxides modified catalysts Ce2O3-Cu-Mn/TiO2 and La2O3-Cu-Mn/TiO2 on the catalytic activity and selectivity of ammonia oxidation were investigated under the reaction condition of 500 ppm ammonia, 1%O2 (vol.%), at the temperature from 125 to 250 °C. The results revealed the beneficial role of Ce2O3 and La2O3 in catalytic activity at low temperature and lean oxygen concentration, while the modification with Ce2O3 and La2O3 led to the negative influence on N2 selectivity. For the catalysts modified with Ce showed lower NO and N2O selectivity than the catalysts modified with La, then the effects of different Ce loadings on catalytic activity and selectivity were also considered, in combination with catalysts preparation methods, which include incipient wet impregnation, sol-gel method and co-precipitation. Results revealed that the catalysts prepared by sol-gel method obtained preferable catalytic activity compared with the others, reaching 99% ammonia at 200 °C, whereas 96% NO was detected. It also indicated that different catalyst preparation method significantly determined production distribution.