Effect of NO₂ on N₂O production and NO_x emission reduction in NH₃ Selective Catalytic Reduction

With the introduction of increasingly strict emission regulations, reducing nitrogen oxide (NO x ) emissions and nitrous oxide (N 2 O) production from diesel engines have become the focus of research. At high temperature, the reaction of NO 2 in the catalyst generates the intermediate product NH 4 NO 3 , which first crystallizes below 300 °C. These crystals tend to block the pores and inhibit the reaction. Subsequently, N 2 O is produced through the decomposition of NH 4 NO 3 , leading to additional pollution. Therefore, the concentration of NO 2 has a direct impact on both the NO x conversion efficiency and the generation of N 2 O, requiring consideration of the optimal proportion of NO 2 in SCR. Considering these two factors, it is concluded that the optimal amount of NO 2 varies with temperature. To improve the NO x conversion rate of the Cu‐SSZ‐13 catalyst at low temperatures and reduce N 2 O generation, the optimal NO 2 ratio of the Cu‐SSZ‐13 catalyst under various operating conditions is studied using numerical simulations. As the temperature rises, the optimal NO 2 /NO x ratio first increases and then decreases. Under the optimal NO 2 /NO x ratio, the NOx conversion rate significantly increases, while N 2 O generation decreases considerably. The optimal NO 2 /NO x ratio also provides suggestions for the optimization of the DOC‐DPF‐DCR system.