Effects of zeolite structure, Cu content, feed gas space velocity, NH3/NOx ratio, and sulfur poisoning on the performance of zeolite-based SCR catalyst 2019-01-0736
To meet mandated increasingly strict regulations for tail pipe emissions of NOx from lean-burn diesel engines, the selective catalytic reduction (SCR) of NOx with NH3 as reducing agent has become an industry norm worldwide. Experiments in the present work included the effects of zeolite structure, Cu content, feed gas space velocity, NH3/NOx ratio, and sulfur poisoning on the performance of zeolite-based SCR catalyst. In the low temperature range (T≤250 ℃), the T50 and T90 of Cu-Beta catalyst are 139 ℃ and 165 ℃, respectively, while the T50 and T90 of Cu-CHA catalyst are 150 ℃ and 183 ℃, respectively. In the high temperature range (T>400 ℃), 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 ℃, and that of Cu-CHA catalyst is 168 to 522 ℃. Cu-CHA catalyst shows better catalytic activity at both 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 high temperature resistance. In the low temperature range, when the gas hourly space velocity (GHSV) is 30000 /h, the NOx conversion is also the highest. It can be concluded that temperature can be the major contributor to catalyst activity of CHA catalyst when the GHSV of feed gas is large. 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 increasing temperature. The NOx conversion decreases from 87% to 63.67% after the operation of the fifth sulfur poisoning. When the temperature is 300 ℃, the catalytic activity of Cu/CHA returns to fresh state’s after the operation of the fifth desulfurization operation.