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

Abstract

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.