Oxidation state of copper species rather than ammonium nitrate decomposition determines the N₂O generation during NO reduction with NH₃ on Cu-AEI catalyst

Cu-based zeolite has excellent performance for nitrogen oxide removal from diesel vehicle exhaust, but a small amount of N₂O is still generated in the selective catalytic reduction (SCR) process, and N₂O has a strong greenhouse effect, which promotes the policy formulation of strictly regulating N₂O emissions. This work systematically investigated the formation mechanism of low temperature N₂O on Cu-AEI catalyst during SCR process. Under both steady and transient state test, the bimodal emission distribution and instantaneous generation behavior of N₂O were observed. In addition, the contribution of NH₄NO₃ pathway to N₂O formation at low temperature in standard SCR (SSCR) was demonstrated by temperature programmed desorption experiment, Thermogravimetric analysis and in situ diffuse fourier transform infrared spectroscopy experiment. NO + NH₃ titration experiment, Raman and density functional theory calculation showed the role of Cu species in low temperature N₂O generation. These results indicate that N₂O formation during SSCR process on Cu-AEI at 200 ℃ is not generated through the decomposition path of NH₄NO₃, but due to the oxidation state of copper species, that is, the side reaction on Cu-peroxo.