Effect of CeO2 for a high-efficiency CeO2/WO3-TiO2 catalyst on N2O formation in NH3-SCR: a kinetic study

In this study, we investigated the effects of CeO2 for a high-efficiency CeO2/WO3-TiO2 catalyst on N2O formation in NH3-SCR reaction using a kinetic method. The results demonstrated that CeO2 is very effective for enhancing the SCR (4NH(3) + 4NO + O-2 -> 4N(2) + 6H(2)O) reaction rate and thus suppressing the NSCR reaction (4NH(3) + 4NO + 3O(2) -> 4N(2)O + 6H(2)O) due to the competition between these two reactions. Therefore, N2O formation under SCR reaction conditions could be remarkably inhibited with the addition of CeO2 to the catalyst. On the other hand, CeO2 can also enhance the C-O reaction (4NH(3) + 5O(2) -> 4NO + 6H(2)O) over the catalyst, so N2O formation under NH3 oxidation conditions was promoted due to the lack of SCR reaction. In addition, we also found another interesting phenomenon wherein N2O formation over WO3-TiO2 (without CeO2) decreased gradually at high temperature from 350 to 450 degrees C, while N2O formation over CeO2/WO3-TiO2 kept increasing with the reaction temperature, which was also associated with the promotional effect of CeO2 on SCR reaction and the competition between SCR and NSCR reactions.