Elucidating the role of O2 in selective catalytic reduction of N2O with CH4 by Operando IR and in situ XAFS-DRIFTS methods

Fe-beta was employed as a representative Fe-zeolite to investigate the effect of O 2 on selective reduction of N 2 O by CH 4 (CH 4 -SCR N2O ). The conversions of CH 4 and N 2 O were decreased in the presence of O 2 , compared with those in the absence of O 2 . Operando IR and in situ XANES–DRIFTS techniques were utilized to elucidate the different behaviors of CH 4 oxidized by N 2 O or O 2 . In the absence of O 2 , Fe(II) species was oxidized by N 2 O to form α-oxygen species, which is reactive to CH 4 to carbon-containing intermediates such as formaldehyde and formate. On the other hand, the reaction of Fe(II) species with N 2 O was inhibited by O 2 present in the reaction, due to the competitive reaction with Fe(II) species, leading to the decreased conversions of both N 2 O and CH 4 . O 2 additionally competes with N 2 O on the oxidation of carbon-containing intermediates such as formaldehyde and formate, which further suppresses N 2 O conversion.