Towards rational design of Cu-SSZ-13 catalysts with less N2O formation in NH3-SCR reaction: The effect of Brønsted acid sites

Ammonia Selective Catalytic Reduction (NHs-SCR) technology has been employed to eliminate NO x from diesel engine exhaust, with Cu-SSZ-13 serving as the commercial catalyst. The greenhouse gas N 2 O is produced as a byproduct when using Cu-SSZ-13 as the NH 3 -SCR catalyst. To achieve synergistic control of pollutants and greenhouse gases in diesel engine exhaust, rational design of Cu-SSZ-13 catalysts is required. In this study, the effect of Brønsted acid sites in Cu-SSZ-13 catalysts on the formation of N 2 O was investigated. Mild thermal treatment was innovatively employed to prepare Cu-SSZ-13 catalysts with different amounts of Brønsted acid sites. EPR, H 2 -TPR, NH 3 -TPD, NMR were utilized to determine that the Brønsted acid sites were modified while the Cu species remained unchanged. Thereby an accurate assessment of the influence of Brønsted acid sites on N 2 O formation could be achieved. Our results showed that Cu-SSZ-13 with more Brønsted acid sites produced less N 2 O during the NH 3 -SCR reaction. In the low-temperature region, the presence of framework acid sites facilitates the decomposition of the NH 4 NO 3 assisted by NO to form N 2 and H 2 O, reducing the formation of N 2 O. In the high-temperature region, the Brønsted acid sites promote the decomposition of NH 2 NO into N 2 and H 2 O. Meanwhile, the N 2 O-SCR reaction can also be promoted by Brønsted acid sites, thereby decreasing N 2 O emissions. This study suggests that in the future design and synthesis of Cu-SSZ-13 zeolites, attention should be paid to creating more Brønsted acid sites in Cu-SSZ-13 to reduce N 2 O emissions.