In-Situ Observation of Reaction Intermediate in the Selective Catalytic Reduction of N_2O with CH4 over Fe Ion-Exchanged BEA Zeolite Catalyst for the Elucidation of Its Reaction Mechanism Using FTIR

摘要

The selective catalytic reduction (SCR) of N2O with CH4 in the absence and presence of excess O_2 has been studied over ion-exchanged Fe-BEA catalyst by the combination of an activity test with in-situ infrared spectroscopy to understand the nature of the surface species involved in the SCR of N2O with CH4.From the results of flow reaction studies,the Fe-BEA catalyst exhibited high activity in the SCR of N_2O with CH_4,even in the presence of excess oxygen,which demonstrates that the active Fe species for the SCR are formed on the ion-exchanged Fe-BEA catalyst.In the FTIR spectra of fresh catalysts,the OH band on Fe ion species (Fe-OH) was observed on the Fe-BEA catalyst,and the Fe-OH species can be involved in the SCR of N_2O with CH_4.Furthermore,the reaction intermediates of methoxy and formate species over the Fe-BEA catalyst were observed during the reaction.We measured the oxidation rates of these surface species with N_2O and O_2,and found that the methoxy species were oxidized with N_2O more rapidly than O_2,while the formate species were oxidized with both N_2O and O_2 at almost the same rate.On the basis of these results,we discuss the reaction mechanism of the SCR of N_2O with CF_4.