CeO2对MnOx催化剂低温脱硝性能的影响及其机理研究

doi:10.15541/jim20250044

摘要/Abstract

摘要： 氮氧化物（NO_x）作为我国主要的大气污染物,通常采用氨气选择性催化还原（NH₃-SCR）技术实现其超低排放。低温NH₃-SCR具有能耗低、成本低等优势备,但在120 ℃条件下,MnO_x基催化剂普遍存在稳定性不足和SO₂、H₂O中毒的问题。为提高MnO_x基催化剂在低温、稀薄烟气条件下的脱硝性能,本研究采用沉淀-焙烧分解法制备了CeO₂/MnO_x催化剂。通过一系列表征手段,系统研究了CeO₂对催化剂结构、表面性质及低温NH₃-SCR性能的影响。结合第一性原理计算,从微观层面揭示了CeO₂对催化机理的影响及其降低反应活化能的内在原因。结果表明,添加CeO₂细化了催化剂微观颗粒尺寸,降低了主晶相MnO₂的占比,显著提升了催化剂的弱酸位点浓度,提高了Mn³⁺/Mn和O_α/O比值,改善了催化剂的表面酸性和氧化还原性能。其中,Mn∶Ce物质的量比为10∶3和10∶5的Mn10Ce3和Mn10Ce5催化剂在120 ℃获得了98%以上的NO转化率和较好的稳定性,且添加CeO₂使团聚态的MnO_x得到分散和Mn⁴⁺分布浓度降低,这在一定程度上阻碍了高价态Mn⁴⁺对NH₃和NO的过度氧化,从而抑制了N₂O的形成,提升了催化剂的N₂选择性。第一性原理计算进一步证实,添加CeO₂可降低反应路径中各中间态的活化能,从而降低反应温度并提高低温NH₃-SCR效率。

关键词: 低温氨气选择性催化还原, CeO₂/MnO_x催化剂, 反应机理

Abstract: Nitrogen oxides (NO_x), as the main atmospheric pollutants in China, are usually removed through ammonia selective catalytic reduction ((NH₃-SCR) technology to achieve ultra-low emissions. Low-temperature NH₃-SCR has gained much attention due to its low energy consumption and cost. However, MnO_x-based catalysts generally suffer from insufficient stability and are susceptible to SO₂ and H₂O poisoning at 120 ℃. To improve the denitrification performance of MnO_x-based catalysts under low temperature and lean flue gas conditions, CeO₂/MnO_x catalysts were prepared by precipitation-calcination decomposition method in this study. The influence of CeO₂ modification on structure, surface properties, and low-temperature NH₃-SCR performance of catalyst was systematically studied. Combining first principles calculations, the influence of CeO₂ modification on catalytic mechanism and underlying reasons for reducing activation energy of the reaction was revealed at microscopic level. The results showed that the addition of CeO₂ refined the micro particle size of catalyst, reduced the proportion of main crystalline phase MnO₂, significantly increased the concentration of weak acid sites in the catalyst, increased the proportion of Mn³⁺/Mn and O_α/O, and improved the surface acidity and redox performance of catalyst. The prepared Mn10Ce3 and Mn10Ce5 catalysts with Mn∶Ce molar ratios of 10∶3 and 10∶5 achieved a NO conversion rate of over 98% and good stability at 120 ℃. The addition of CeO₂ dispersed the aggregated MnO_x and reduced the concentration of Mn⁴⁺ distribution, which to some extent hindered the excessive oxidation of NH₃ and NO by high valence Mn⁴⁺, thereby suppressing N₂O formation and improving N₂ selectivity of the catalyst. First principles calculations further confirmed that CeO₂ modification reduced the activation energy of various intermediate states in the reaction pathway, thereby lowering the reaction temperature and improving the low-temperature NH₃-SCR efficiency.

Key words: low-temperature ammonia selective catalytic reduction, CeO₂/MnO_x catalyst, reaction mechanism

中图分类号:

X701

邬博宇, 张深根, 张生杨, 刘波, 张柏林. CeO₂对MnO_x催化剂低温脱硝性能的影响及其机理研究[J]. 无机材料学报, DOI: 10.15541/jim20250044.

WU Boyu, ZHANG Shengen, ZHANG Shengyang, LIU Bo, ZHANG Bolin. Effect of CeO₂ on Low-temperature Denitrification Performance of MnO_x Catalysts and Its Mechanism[J]. Journal of Inorganic Materials, DOI: 10.15541/jim20250044.

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CeO₂对MnO_x催化剂低温脱硝性能的影响及其机理研究

Effect of CeO₂ on Low-temperature Denitrification Performance of MnO_x Catalysts and Its Mechanism

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