Effect of Cu Concentration on the Selective Catalytic Reduction of NO with Ammonia for Aluminosilicate Zeolite SSZ-13 Catalysts

The influence of Cu concentration on the selective catalytic reduction (SCR) of NO with ammonia (NH3-SCR) for copper-exchanged aluminosilicate zeolite catalysts (Cu-SSZ-13) was investigated. The results demonstrate that the SCR performance of the catalysts increases initially and decreases subsequently with an increase in Cu concentration in the low-temperature region (100-300 degrees C). The highest low-temperature SCR activity (lightoff temperature is 149 degrees C) is obtained in the Cu-0.100-SSZ-13 catalyst, i.e., the concentration of the Cu salt solution reaches up to 0.100 mol/L. BET and XRD results illustrate that the concentration of the Cu salt solution does not have a significant effect on the structure of the samples. The NH3-TPD and H-2-TPR outcomes demonstrate that the amount of Lewis acidity and isolated Cu2+ on Cu-SSZ-13 catalysts increases as the CuCl2 concentration increases from 0 to 0.125 mol/L. However, most of the H+ in the Bronsted acid sites (Si-OH-Al) are replaced by isolated Cu2+, which limits the storage and transfer capacity of ammonia. As a result, the catalytic efficiency of Cu-SSZ-13 reduces with a further increase in CuCl2 concentration.