Nb对FeCeO_(x)催化剂NH_(3)选择性催化还原NO的促进机制

Mechanism for Nb promoting NO selective catalytic reduction with NH_(3)over FeCeO_(x) catalysts

以NH_(3)为还原剂的选择性催化还原(NH_(3)-SCR)是消除大气重要污染物氮氧化物(NO_(x))的关键技术之一。采用共沉淀法制备了一系列Nb促进的Nb_(a)Fe_(1-a)CeO_(x)(a=0、0.1、0.2、0.4)催化剂用于NH_(3)选择性催化还原NO反应,并利用BET、XRD、XRF、NH_(3)-TPD、H_(2)-TPR、in situ DRIFTS等技术对催化剂的物理化学性质进行表征。结果表明:Nb的引入能显著提升FeCeO_(x)催化剂的中低温脱硝性能,其中,Nb_(0.1)Fe_(0.9)CeO_(x)催化剂在175~350℃温度区间内获得超过80%的NO_(x)转化率,显示出优异的中低温NH_(3)-SCR催化活性。进一步分析发现,Nb_(0.1)Fe_(0.9)CeO_(x)催化剂上的SCR反应主要遵从Eley-Rideal反应机理,适量Nb的引入使得Nb、Fe、Ce之间产生了强相互作用,不仅可以降低催化剂的结晶度,增加催化剂的比表面积,还有利于氧化还原能力和表面酸量的提升,进而有助于NH_(3)的吸附、活化以及NH_(3)-SCR反应活性的增强。

The selective catalytic reduction with NH_(3)(NH_(3)-SCR)is one of the most prominent technologies to eliminate the important pollutants of nitrogen oxides(NO_(x))in the atmosphere.A series of Nb promoted Nb_(a)Fe_(1-a)CeO_(x)(a=0,0.1,0.2,0.4)catalysts were prepared by co-precipitation method for NH_(3)-SCR of NO.The physical and chemical properties of the catalysts were characterized by BET,XRD,XRF,NH_(3)-TPD,H_(2)-TPR and in situ DRIFTS.Results showed that the introduction of Nb significantly improved the low-and mid-temperature denitration performance of the FeCeO_(x)catalysts.The Nb_(0.1)Fe_(0.9)CeO_(x)catalyst achieved more than 80%of NO_(x)conversion rate between 175℃and 350℃,exhibiting the best NH_(3)-SCR activity among the prepared Nb_(a)Fe_(1-a)CeO_(x)catalysts.The SCR reaction on the Nb_(0.1)Fe_(0.9)CeO_(x)catalyst followed the Eley-Rideal reaction mechanism,and its excellent SCR performance could be ascribed to the strong interaction between Nb,Fe and Ce due to the introduction of appropriate amount of Nb,which decreased the crystallinity,increased the specific surface area and gave rise to the redox property of the catalyst.The adsorption and activation of NH_(3)were also encouraged by the enhanced surface acidity.