Wu Zhongbiao, Jiang Boqiong, Liu Yue, Wang Haiqiang, Jin Ruiben
Department of Environmental Engineering, Zhejiang University, Hangzhou 310027, China.
Environ Sci Technol. 2007 Aug 15;41(16):5812-7. doi: 10.1021/es0700350.
Manganese oxides and iron-manganese oxides supported on TiO2 were prepared by the sol-gel method and used for low-temperature selective catalytic reduction (SCR) of NO with NH3. Base on the previous study, Mn(0.4)/ TiO2 and Fe(0.1)-Mn(0.4)/TiO2 were then selected to carry out the in situ diffuse reflectance infrared transform spectroscopy (DRIFT) investigation for revealing the reaction mechanism. The DRIFT spectroscopy for the adsorption of NH3 indicated the presence of coordinated NH3 and NH4+ on both of the two catalysts. When NO was introduced, the coordinated NH3 on the catalyst surface was consumed rapidly, indicating these species could react with NO effectively. When NH3 was introduced into the sample preadsorbed with NO + O2, SCR reaction would not proceed on Mn(0.4)/TiO2. However, for Fe(0.1)-Mn(0.4)/ TiO2 the bands due to coordinated NH3 on Fe2O3 were formed. Simultaneously, the bidentate nitrates were transformed to monodentate nitrates and NH4+ was detected. And NO2 from the oxidation of NO on catalyst could react with NH4+ leading to the reduction of NO. Therefore, it was suggested that the SCR reaction on Fe(0.1)-Mn(0.4)/TiO2 could also take place in a different way from the reactions on Mn(0.4)/TiO2 proposed by other researchers. Furthermore, the SCR reaction steps for these two kinds of catalysts were proposed.
采用溶胶 - 凝胶法制备了负载在TiO₂上的锰氧化物和铁 - 锰氧化物，并将其用于NH₃低温选择性催化还原（SCR）NO。基于前期研究，选取Mn(0.4)/TiO₂和Fe(0.1)-Mn(0.4)/TiO₂进行原位漫反射红外变换光谱（DRIFT）研究以揭示反应机理。NH₃吸附的DRIFT光谱表明两种催化剂表面均存在配位NH₃和NH₄⁺。引入NO时，催化剂表面的配位NH₃迅速消耗，表明这些物种可与NO有效反应。当将NH₃引入预先吸附有NO + O₂的样品中时，Mn(0.4)/TiO₂上不会发生SCR反应。然而，对于Fe(0.1)-Mn(0.4)/TiO₂，在Fe₂O₃上形成了由配位NH₃引起的谱带。同时，双齿硝酸盐转变为单齿硝酸盐并检测到NH₄⁺。并且催化剂上NO氧化产生的NO₂可与NH₄⁺反应导致NO的还原。因此，表明Fe(0.1)-Mn(0.4)/TiO₂上的SCR反应也可能以与其他研究人员提出的Mn(0.4)/TiO₂上的反应不同的方式进行。此外，还提出了这两种催化剂的SCR反应步骤。
