球形活性炭担载MnOx-CeO2和三聚氰胺的低温脱硝行为研究

以MnO_x-CeO₂为活性组分, 以三聚氰胺为还原剂, 制备了球形活性炭(SAC)担载MnO_x-CeO₂和三聚氰胺的复合催化剂, 并考察了该催化剂在低温下(120~180℃)对NO的选择性催化还原(SCR)反应行为。实验还利用扫描电子显微镜-能谱仪(SEM-EDS)、X射线衍射(XRD)和低温N₂吸附法等技术对催化剂进行了表征。结果表明, 当反应温度为180℃、空速为6000 h^-1、NO和O₂浓度分别为0.1%和8%时, 担载8% Mn(摩尔比Mn:Ce固定为1:1)和10%三聚氰胺的催化剂可在8.8 h内实现99%的NO_x转化率。煅烧温度高于400℃将促使MnO_x-CeO₂形成更大的晶体颗粒和更加规整的晶型结构, 从而降低其melamine-SCR活性。三聚氰胺担载量高于15%将造成催化剂比表面积和孔容的急剧减小, 最终导致其稳态NO_x转化率的下降。而金属氧化物担载量的增加和反应温度的升高都有利于Melamine-SCR反应, 且在较宽的NO和O₂浓度范围内, 催化剂的稳态NO_x转化率都能维持在99%左右。

Low-temperature Removal of NO by Spherical Activated Carbon Loaded with MnOx-CeO2 and Melamine

A spherical activated carbon (SAC) loaded with MnO_x-CeO₂ and melamine was prepared as the catalyst for selective catalytic reduction (SCR) of NO at low temperature (120-180℃). Physical and chemical properties of the catalysts were characterized by scanning electron microscopy-energy dispersive spectrometer (SEM-EDS), X-ray diffraction (XRD), and N₂ adsorption-desorption technologies, respectively. The results show that about 99% NO_x conversion for 8.8 h at 180℃ is achieved over the catalyst with 10% melamine and 8% Mn loading (the mole ratio of Mn:Ce was fixed at 1:1) under the condition of 0.1% NO, 8% O₂ and a space velocity of 6000 h^-1. When the calcination temperature is higher than 400℃, the melamine-SCR activity is decreased obviously due to the crystallinity of the metal oxides increasing. When melamine loading is more than 15%, the specific surface area and pore volume of the catalysts decrease significantly, leading to a decline in the stationary-state NO_x conversion. However, the increase of metal oxides loading and reaction temperature is found to be beneficial to melamine-SCR reactivity, and the stationary-state NO_x conversion is always maintained at about 99% over a wide concentration range of NO and O₂.