Experimental Studies on NO_<i>x</i> Removal and Soot Regeneration Characteristics of a Selective Catalytic Reduction Filter

Herein, the NOx removal capability of SCRF based on the Cu/SSZ-13 catalyst and its influencing factors were comprehensively explored. The reaction characteristics of important reactions in SCRF including SCR, fast SCR, NH3 oxidation, etc. under different soot contents were studied under quasi-steady-state experimental conditions, as well as the influence of reactant conditions on soot regeneration. The results indicated the following: Cu/SSZ-13 SCRF achieves NOx conversion efficiency exceeding 90% at 250 °C, comparable to through-flow SCR. Fast SCR performance is over 20% better than that of standard SCR at 200 °C, while NO2–SCR shows the lowest NOx removal. A significant amount of N2O is generated, with NH4NO3 formation impeding the SCR reaction. An NO2/NOx ratio of 0.4 enhances NOx removal. To limit NH4NO3 formation at low temperatures, an NH3/NOx ratio of 0.8 or lower is advised below 200 °C; above this temperature, the ratio should exceed 1 due to strong ammonia oxidation. Soot loading hinders NOx removal at 200–500 °C but enhances it above 500 °C. NH3-TPD, NH3-TPO, and N2O generation experiments indicate that NH3 adsorption sites exist on soot, covering the Cu-based catalyst surface. Quasi-steady state SCR tests show that while the SCR reaction does not actively regenerate soot, it strongly inhibits passive regeneration. Under NO2 intake, the level of CO2 from passive regeneration at 300 °C increased by 175 ppm, indicating competition with NO2.