MnO_(x)-CeO_(2)催化剂中元素价态对低温SCR还原NO_(x)性能的影响

Influence of Valence in MnO_(x)-CeO_(2)Catalysts on Low-temperature Selective Catalytic Reduction of NO_(x)

采用具有MOFs结构的Ce-MOFs作为前驱体,制备了一系列不同Ce4+离子浓度的CeO_(2),然后负载MnO_(x)制备MnO_(x)-CeO_(2)催化剂,研究发现热处理工艺可以有效调控催化剂中Mn元素和Ce元素的化合价,从而调控催化活性。其中700℃焙烧的CeO_(2)载体负载MnO_(x)后经过300℃热处理制备的催化剂,具有最高脱硝活性,在150~200℃的温度区间NO_(x)转化率接近100%。X射线衍射(XRD)、扫描电镜(SEM)、NH_(3)程序升温脱附(NH_(3)-TPD)、NO温度程序脱附(NO-TPD)等分析显示,在MnO_(x)-CeO_(2)催化剂上SCR脱硝反应主要遵循L-H路径,催化剂中的高浓度Ce^(4+)离子、Mn^(2+)离子和Mn^(3+)离子,有利于催化剂的低温SCR脱硝活性,而Mn4+离子并不是催化剂的最佳活性成分。

A series of CeO_(2)with different Ce4+ion concentrations were prepared by using Ce-MOFs with MOFs structure as a precursor,MnO_(x)-CeO_(2)catalyst was prepared by loading MnO_(x),and it was found that the heat treatment processes could effectively regulate the valence states of Mn and Ce elements in the catalyst,thereby regulate the performance of the catalyst.The catalyst prepared by heating at 300℃after MnO_(x)loaded on 700℃-annealed CeO_(2)powder shows the highest catalytic activity with approximately 100%NO_(x)conversion in the temperature window of 150℃to 200℃.XRD,SEM and NH_(3)/NO-TPD analyses confirmed that the SCR reaction follows the L-H pathway,and the high concentration of Ce^(4+)ions,Mn^(2+)ions and Mn^(3+)ions in the catalyst was conducive to the low-temperature SCR denitrification activity of the catalyst,while Mn4+ions were not the active component.