Selective catalytic reduction of N2O with C3H6 over Fe-ZSM5 catalyst in the presence of excess O2: The correlation between the induction period and the surface species produced

Abstract

The catalytic activity of N₂O reduction over Fe-ZSM5 prepared by an ion exchange method was significantly increased by adding C₃H₆, even in the presence of excess O₂, i.e., selective catalytic reduction (SCR) of N₂O occurred with C₃H₆. We found that there was an induction period for the increase in activity after adding C₃H₆ to the N₂O–O₂ flow. Another induction period was also observed for the decrease in activity after removing C₃H₆ or O₂–C₃H₆ from the N₂O–O₂–C₃H₆ mixture. The length of the induction period was influenced by the partial pressure of C₃H₆, the composition of the reaction gases and the reaction temperature. During the latter induction period, CO₂, H₂O and N₂ were detected as products. These results suggest that adsorbed surface species such as C_xH_y(a) and/or C_xH_yO_z(a), produced by the reaction in the N₂O–O₂–C₃H₆ mixture, reacted with N₂O or N₂O–O₂ to produce CO₂, H₂O and N₂. In situ DRIFT studies showed the formation of C_xH_y(a) and/or C_xH_yO_z(a) species during the N₂O–O₂–C₃H₆ reaction, the behavior of which (formation and reactivity) correlated well with the induction period phenomenon.