Abstract:

Selective catalytic reduction(SCR) is currently the most widely used industrial NO _x removal technology. TiO₂ supported vanadium-based catalysts are the most widely used commercial catalysts. However, there are still many problems to be addressed, such as poor low-temperature (<300℃) activity, narrow temperature activity window (300—400℃), and high vanadium toxicity, which limits their application in low temperature flue gas industry. Consequently, the development of high-performance low-temperature SCR catalysts is an important direction of research. Mn and Ce, due to their good low-temperature performance, were selected as the active components, and Mo doping was used to enhance the SO₂ resistance of the catalyst. The catalyst samples were characterized by N₂ adsorption and desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR). The results showed that the presence of SO₂ lowered the NH₃-SCR activity of the Mn_2.5Ce₁/SiC catalyst, while Mo modification could reduce the inhibitory effect. SO₂ would compete with NH₃ for adsorption on the catalyst surface, thereby inhibiting the NH₃-SCR activity of the catalyst. When the molar ratio of Mn∶Ce∶Mo was 2.5∶1∶0.07, the catalyst achieved the best performance, of which the denitrification performance and anti-SO₂ poisoning performance were better than that of the Mn_2.5Ce₁/SiC catalyst without Mo doping. The Mo modification increased the adsorbed oxygen content on the catalyst surface and weakened the poisoning effect of SO₂ on the catalyst surface.

Key words: selective catalytic reduction (SCR), catalyst, low-temperature, flue gas, coal combustion, Mo modification

摘要：

选择性催化还原（selective catalytic reduction，SCR）是目前应用最广泛的工业氮氧化物脱除技术。以TiO₂为载体的钒基催化剂是应用最多的商业催化剂，但依然存在很多问题，如低温（<300℃）工况下活性较差、温度窗口较窄（300~400℃）、含钒物质毒性较强等，限制了其在低温烟气行业的应用。因此，开发高性能的低温SCR催化剂是研究的一个重要方向。选取低温性能较好的Mn和Ce作为活性组分，并且掺杂Mo用于提升催化剂的抗SO₂性能。通过N₂吸脱附、X射线衍射（XRD）、X射线光电子能谱（XPS）及傅里叶变换红外光谱（FTIR）等方法对催化剂样品进行了表征分析。结果表明：SO₂的存在会抑制Mn_2.5Ce₁/SiC催化剂的NH₃-SCR活性，Mo改性可以减弱SO₂对催化剂脱硝活性的抑制作用。SO₂会在催化剂表面与NH₃发生竞争吸附，从而抑制催化剂的NH₃-SCR活性。当Mn∶Ce∶Mo的摩尔比为2.5∶1∶0.07时，获得最佳的脱硝性能和抗SO₂中毒性能。通过Mo改性增加了催化剂表面吸附氧的含量，并且减弱了SO₂对催化剂表面的毒害作用。

关键词: 选择催化还原, 催化剂, 低温, 烟道气, 煤燃烧, Mo 改性