Yang Yang, Hu Zhun, Mi Rongli, Li Dan, Yong Xiang, Yang Huie, Liu Kunfeng
Institute of Industrial Catalysis, School of Chemical Engineering and Technology, Xi'an Jiaotong University Xi'an Shaanxi 710049 China
Sinochem Modern Environmental Protection Chemicals (Xi'an) Co. LTD. Xi'an Shaanxi 710201 China.
RSC Adv. 2019 Feb 6;9(9):4682-4692. doi: 10.1039/c8ra10077b. eCollection 2019 Feb 5.
A series of manganese-based catalysts supported by 5-10 nm, 10-25 nm, 40 nm and 60 nm anatase TiO particles was synthesized an impregnation method to investigate the effect of the initial support particle size on the selective catalytic reduction (SCR) of NO with NH. All catalysts were characterized by transmission electron microscopy (TEM), N physisorption/desorption, X-ray diffraction (XRD), temperature programmed techniques, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared transform spectroscopy (DRIFTS). TEM results indicated that the particle sizes of the MnO /TiO catalysts were similar after the calcination process, although the initial TiO support particle sizes were different. However, the initial TiO support particle sizes were found to have a significant influence on the SCR catalytic performance. XPS and NH-TPD results of the MnO /TiO catalysts illustrated that the surface Mn/Mn molar ratio and acid amount could be influenced by the initial TiO support particle sizes. The order of surface Mn/Mn molar ratio and acid amount over the MnO /TiO catalysts was as follows: MnO /TiO(10-25) > MnO /TiO(40) > MnO /TiO(60) > MnO /TiO(5-10), which agreed well with the order of SCR performance. DRIFTS results revealed that the NH-SCR reactions over MnO /TiO at low temperature occurred a Langmuir-Hinshelwood mechanism. More importantly, it was found that the bridge and bidentate nitrates were the main active substances for the low-temperature SCR reaction, and bridge nitrate adsorbed on Mn showed superior SCR activity among all the adsorbed NO species. The variation of the initial TiO support particle size over MnO /TiO could change the surface Mn/Mn molar ratio, which could influence the adsorption of NO species, thus bringing about the diversity of the SCR catalytic performance.
通过浸渍法合成了一系列负载有5 - 10纳米、10 - 25纳米、40纳米和60纳米锐钛矿型TiO₂颗粒的锰基催化剂，以研究初始载体粒径对NH₃选择性催化还原（SCR）NO的影响。所有催化剂均通过透射电子显微镜（TEM）、N₂物理吸附/脱附、X射线衍射（XRD）、程序升温技术、X射线光电子能谱（XPS）和漫反射红外变换光谱（DRIFTS）进行表征。TEM结果表明，尽管初始TiO₂载体粒径不同，但煅烧后MnOₓ/TiO₂催化剂的粒径相似。然而，发现初始TiO₂载体粒径对SCR催化性能有显著影响。MnOₓ/TiO₂催化剂的XPS和NH₃-TPD结果表明，表面Mn/Mn摩尔比和酸量会受到初始TiO₂载体粒径的影响。MnOₓ/TiO₂催化剂表面Mn/Mn摩尔比和酸量的顺序如下：MnOₓ/TiO₂(10 - 25) > MnOₓ/TiO₂(40) > MnOₓ/TiO₂(60) > MnOₓ/TiO₂(5 - 10)，这与SCR性能顺序非常吻合。DRIFTS结果表明，MnOₓ/TiO₂在低温下的NH₃-SCR反应遵循Langmuir-Hinshelwood机理。更重要的是，发现桥式和双齿硝酸盐是低温SCR反应的主要活性物质，并且吸附在Mn上的桥式硝酸盐在所有吸附的NOₓ物种中表现出优异的SCR活性。MnOₓ/TiO₂上初始TiO₂载体粒径的变化会改变表面Mn/Mn摩尔比，这会影响NOₓ物种的吸附，从而导致SCR催化性能的多样性。
