Cu掺杂对Pt/Ba/CuxMg1-xAl2O4催化剂高温稀燃NOx消除性能的影响

制备了一系列不同Cu掺杂量的Pt/Ba/Cu_xMg_1-xAl₂O₄(x=0, 0.1, 0.3)催化剂, 将其应用于高温NO_x储存还原(NSR)反应, 并探究了Cu掺杂量对催化剂NO_x消除性能的影响. 结果表明, 储存组分BaCO₃在NSR过程中存在再分散现象. 高温时催化剂的NO_x消除性能取决于其NO_x储存量, 而不是NO氧化和NO_x还原性能. 高温时催化剂的NO_x储存量与其上硝酸盐的热稳定性密切相关, Pt/Ba/MgAl₂O₄上NO_x主要以离子态硝酸盐形式存在, 而掺杂Cu后催化剂上的NO_x又增加了单齿硝酸盐的存在形式, 单齿硝酸盐具有更高的热稳定性, 因此掺Cu催化剂具有更大的NO_x储存量. 在450~500 ℃范围内, Cu的掺杂显著提高了Pt/Ba/MgAl₂O₄的NO_x消除性能; Pt/Ba/Cu_0.1Mg_0.9Al₂O₄催化剂的性能最佳, 450 ℃时的NO_x消除效率高达90%.

Effect of Copper Doping on Lean NOx Trap Performance of Pt/Ba/CuxMg1-xAl2O4 Catalysts at High Temperatures †

A series of Pt/Ba/Cu_xMg_1-xAl₂O₄ catalysts with Cu doping was synthesized and used in high-temperature NO_x storage reduction reaction. The results demonstrate that BaCO₃, the NO_x storage component, redisperses in the NO_x storage reduction process. Moreover, the De-NO_x activity of the catalysts at high temperatures was determined by the NO_x storage capacity, rather than the NO oxidation and NO_x reduction ability of the catalysts. The NO_x storage capacity of the catalysts is directly linked to the thermal stability of nitrate species stored on the catalysts. NO_x mainly exists in the form of ionic nitrate species on Pt/Ba/MgAl₂O₄, while NO_x mainly co-exists as ionic nitrate and monodentate nitrate species on the Cu-doped catalysts. We discovered that monodentate nitrate species show higher thermal stability than ionic nitrate species. As a result, the Cu-doped catalysts exhibit the larger NO_x storage capacity and hence the higher De-NO_x activity. At the temperature range from 450 ℃ to 500 ℃, the addition of Cu greatly enhanced the NO_x removal percentage of the catalysts. Among all the catalysts, Pt/Ba/Cu_0.1Mg_0.9Al₂O₄ has the highest De-NO_x activity with NO_x removal percentage about 90% at 450 ℃.