2004 Volume 25 Issue 8 Pages 505-512
The selective catalytic reduction (SCR) of N2O with CH4 in the presence of excess O2 was studied over ion-exchanged Fe-BEA catalyst by the observation of reaction intermediates in order to elucidate the reaction mechanism. From the results of activity tests, SCR of N2O with CH4 in the presence of excess O2 proceeded at much lower reaction temperature than N2O decomposition over the Fe-BEA catalyst. The profiles of temperature programmed desorption of O2 after N2O pretreatment gave a new desorption peak at lower desorption temperatures compared to the case of O2 pretreatment. However, the oxygen species desorbed at the lower temperatures did not react with CH4 in the profiles of temperature programmed reaction. From the structural analysis by means of extended X-ray absorption fine structure, a Fe-Fe bond was observed on the Fe-BEA catalyst after N2O treatment. This suggests that binuclear species can be formed over the Fe-BEA catalyst. In the in-situ FTIR observation, the methoxy and formate species were observed during the SCR reaction. We measured the reaction rates of these surface species with N2O and O2, and this is related to the selective reduction of N2O with CH4.
