钾负载量对CuO/K2CO3/MgAl2O4催化剂高温NOx储存还原性能的影响

Effect of Potassium Loading on the NO_x Storage and Reduction Performance of the CuO/K_2CO_3/MgAl_2O_4 Catalyst at High Temperature

制备了适用于高温氮氧化物储存还原(NSR)反应的Cu O/K_2CO_3/MgAl_2O_4非贵金属催化剂,考察了钾负载量对催化剂NSR性能的影响,发现钾主要以高分散K_2CO_3和体相K_2CO_3的形式存在.在稀燃条件下,NOx在体相K_2CO_3上形成了高温稳定的硝酸盐物种,而高分散K_2CO_3上形成的硝酸盐的高温稳定性则较差.当钾负载量较低时,催化剂的NOx储存能力有限,K_2CO_3主要以高分散形式存在,稀燃阶段形成的硝酸盐的热稳定性较低,高温NSR活性较低;而钾负载量过高时,K_2CO_3则会覆盖Cu O活性位,从而降低催化剂的NSR活性.在450℃的高温条件下,钾负载量为10%时,所制备催化剂的NOx储存还原能力最佳,NOx还原效率达到99.9%,是一种具有潜在应用前景的高温NSR催化剂.

We designed a new NOxstorage and reduction（NSR） CuO/K2CO3/Mg Al2 O4 catalyst operating at high temperature. The effect of potassium loading on the NOxstorage and reduction performance of the catalyst was studied. In the catalyst,the K_2CO_3 exists as highly dispersed K_2CO_3 and bulk K_2CO_3. In the lean-burn period,the nitrates formed on the bulk K_2CO_3 have high thermal stability at high operating temperature,while the thermal stability of the nitrates formed on the highly dispersed K_2CO_3 is low. When the K loading is low,the K_2CO_3 mainly exists as highly dispersed K_2CO_3,the limited NOxstorage capacity and the low thermal stability of the nitrates result in the low NSR activity at high temperature. While too much K_2CO_3 loaded on the catalyst can decrease the redox ability of CuO by covering it,which will decrease the NSR activity of the catalysts. When the K loading is 10%,the best NSR activity is obtained with the highest NOxreduction percentage of 99. 9% at 450 ℃. Therefore,the CuO/K_2CO_3/Mg Al2 O4 catalyst is a promising high-temperature NSR catalyst.