原位漫反射傅里叶变换红外光谱研究锰铁基催化剂上低温选择性催化还原反应机理(英文)

In situ DRIFTS study of the mechanism of low temperature selective catalytic reduction over manganese-iron oxides

采用自蔓延燃烧法制备了Ti0.9Mn0.05Fe0.05O2-δ催化剂,运用原位漫反射傅里叶变换红外光谱对该催化剂的NO和NH3稳态吸附以及NO和NH3瞬态反应进行了详细地分析与讨论.结果表明,相比于Lewis酸性位,150 oC时Brnsted酸性位吸附的NH3更具有SCR活性;与双齿硝酸盐和桥式硝酸盐相比,NO吸附产生的单齿硝酸盐是主要的中间物种;该SCR反应遵循Eley-Rideal和Langmuir-Hinshelwood机理,但以后者为主.另外,O2的存在有利于NO的氧化和配位态NH3的活化.

To investigate the mechanism of selective catalytic reduction （SCR） of NOx with NH3, Ti0.9Mn0.05Fe0.05O2-δ catalyst was prepared by self-propagating high-temperature synthesis （SHS） method and evaluated at 25-450 ℃. The catalyst was characterized by X-ray diffraction （XRD） and transmission electron microscopy （TEM）. The possible SCR mechanism over Ti0.9Mn0.05Fe0.05O2-δ was studied by in situ diffuse reflectance infrared Fourier transform spectroscopy （DRIFTS）. Ti0.9Mn0.05Fe0.05O2-δ showed both high SCR activity and N2 selectivity over a broad temperature win-dow of 100-350 ℃. The XRD and TEM results indicated that the active components of Mn and Fe were in a highly dispersed state and in an amorphous form on TiO2. The DRIFTS results revealed that Bronsted acid sites were the active centers for NO removal and monodentate nitrates were the key intermediate in the SCR reaction. At 150 ℃, both Langmuir-Hinshelwood and Eley-Rideal mechanisms are involved in the SCR reaction, while the former one mechanism dominates the cata-lytic activity of Ti0.9Mn0.05Fe0.05O2-δ. Additionally, the presence of O2 significantly affects NO oxidation and coordinated NH3 activation.