Selective catalytic reduction (SCR) of N2O With C2H6 took place effectively over Fe ion-exchanged BEA zeolite catalyst (Fe-BEA) even in the presence of excess oxygen. The mechanism in the SCR of N2O with C2H6 over Fe-BEA catalyst was studied by a transient response experiment and an in situ DRIFT spectroscopy. No oxidation of C2H6 by O-2 took place below 350 degreesC (in C2H6/O-2). In the N2O/C2H6/O-2 system, however, it was found that the reaction of C2H6 with O-2 was drastically enhanced by the presence of N2O even at low temperatures (200-300 degreesC). Therefore, it was concluded that N2O played an important role in the oxidation of C2H6 (i.e., activation of C2H6 at an initial step). On the basis of these findings, the mechanism in the SCR of N2O with C2H6 is discussed.