Effects of Zeolite Structure, Cu Content, Feed Gas Space Velocity, NH ₃ /NOx Ratio, and Sulfur Poisoning on the Performance of Zeolite-Based SCR Catalyst 2019-01-0736

To meet the increasingly stringent nitrogen oxides (NOx) emission regulations of diesel engines, the selective catalytic reduction (SCR) of NOx with ammonia (NH₃) has become the current mainstream technical route. Experiments in the present study included the performance of Cu-Beta catalyst and Cu-CHA catalyst before and after hydrothermal aging, and the effects of Cu content, feed gas space velocity (GHSV), NH₃/NOx ratio, and sulfur poisoning on the performance of Cu-CHA catalyst. In the low temperature range (T≤250 °C), the T₅₀ and T₉₀ of Cu-Beta catalyst are 139 °C and 165 °C, respectively, while those of Cu-CHA catalyst are 150 °C and 183 °C, respectively. In the high temperature range (T>400 °C), the NOx conversion of Cu-CHA catalyst is generally higher than that of Cu-Beta catalyst. The temperature window of Cu-Beta catalyst is 154 to 514 °C, while that of Cu-CHA catalyst is 168 to 522 °C. Cu-CHA catalyst exhibits better catalytic activity at medium and high temperatures. It can be concluded that the lower the Cu content of CHA catalyst, the lower the T₅₀, but the better the thermal stability. In the low temperature range, when the gas hourly space velocity (GHSV) is 30000/h, the NOx conversion is also the highest. The effect of NH₃/NOx ratio on catalytic activity of Cu-CHA catalyst is significant at high temperature. When the ratio is 0.8, the NOx conversion decreases linearly with the increase of temperature. After the fifth sulfur poisoning operation, the NOx conversion decreases from 87% to 63.7%. When the temperature is 300 °C, the catalytic activity of Cu-CHA restores to fresh state after the operation of the fifth desulfurization operation.