Experimental Investigation on N₂O Formation during the Selective Catalytic Reduction of NOx with NH₃ over Cu-SSZ-13

N₂O formation over Cu-SSZ-13 during selective catalytic reduction (SCR) of NOx with NH₃ under different conditions was experimentally investigated based on a flow reactor and in situ diffused reflectance infrared Fourier transform spectroscopy experiments. The results show that the NSCR and the nonselective NH₃ oxidation are the major pathways for N₂O formation over Cu-SSZ-13. N₂O formation at low and high temperatures usually occurs via different mechanisms. The N₂O formation at low temperatures is mainly ascribed to the decomposition of NH₄NO₃, which mainly forms on Cu(OH)⁺, while at high temperatures, N₂O is formed because of the NH₃ oxidation by O₂ and NOx. Besides, the effect of ANR, NO₂/NOx ratio, and O₂ and H₂O concentrations on N₂O formation were also studied. They all affect N₂O formation, and the effects on the two mechanisms are totally different at low and high temperatures.