K和Cu部分取代对LaMnO3钙钛矿型催化剂同时去除NOx和碳烟的影响

 用K部分取代LaMnO3中的La得到La0.8K0.2MnO3, 再用Cu部分取代Mn得到La0.8K0.2CuxMn1-xO3, 采用程序升温反应方法对催化剂同时去除NOx和碳烟的性能进行评价,然后利用XPS从分子水平来解释部分取代对LaMnO3钙钛矿催化剂性能的影响. 结果表明,两种不同取代更有利于催化剂形成钙钛矿型晶体结构,为了保持分子的电中性, K部分取代使得Mn2+转变成Mn3+, 部分转变成Mn4+, 从而使催化剂的活性及选择性大幅度提高. Cu部分取代进一步使部分Mn3+转变成Mn4+, 催化剂的活性有所降低,但由于Cu2+和Mn3+的协同作用,催化剂的选择性得到进一步的提高. 对于同时催化去除NOx和碳烟反应,催化剂中起决定性作用的是表面的Mn3+和Cu2+.

Effect of Partial Substitution of K and Cu in LaMnO3 on Simultaneously Catalytic Removal of NOx and Soot

La_ 0.8K_ 0.2MnO_3 and La_ 0.8K_ 0.2Cu_xMn_ 1-xO_3 was prepared by partial substitution of K for La in {LaMnO_3} and further partial substitution of Cu for Mn,respectively.The catalytic properties of the two catalysts for simultaneous removal of NO_x and soot were evaluated through the temperature-programmed reaction technique.X-ray photoelectron spectroscopy(XPS)was adopted to investigate the effect of partial substitution from the aspect of the catalyst composition.The X-ray diffraction results showed that the two kinds of substitution promoted the formation of perovskite.To maintain the electroneutrality,Mn 2 turned to Mn 3 and even some Mn 4 after the partial substitution of K for La,which greatly improved both the activity and the selectivity of the catalysts.The partial substitution of Cu for Mn further promoted the transition of Mn 3 to Mn 4 ,which deactivated the catalysts a little but improved the selectivity of the catalysts again owing to the synergistic effects of Cu 2 and Mn 3 .The XPS results indicated that surface Mn 3 and Cu 2 were the effective ions for the simultaneously catalytic removal of NO_x and soot.