Mechanism of the Selective Catalytic Oxidation of Slip Ammonia over Ru-Modified Ce鈥揨r Complexes Determined by in Situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy

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• 作者：Wanmiao Chen ; Yongpeng Ma ; Zan Qu ; Qinghang Liu ; Wenjun Huang ; Xiaofang Hu ; Naiqiang Yan
• 刊名：Environmental Science & Technology
• 出版年：2014
• 出版时间：October 21, 2014
• 年：2014
• 卷：48
• 期：20
• 页码：12199-12205
• 全文大小：466K
• ISSN：1520-5851

文摘

The slip ammonia from selective catalytic reduction (SCR) of NO_x in coal-fired flue gas can result in deterioration of the utilities or even the environmental issues. To achieve selective catalytic oxidation (SCO) of slip ammonia, Ru-modified Ce鈥揨r solid solution catalysts were prepared and evaluated under various conditions. It was found that the Ru/Ce_0.6Zr_0.4O₂(polyvinylpyrrolidone (PVP)) catalyst displayed significant catalytic activity and the slip ammonia was almost completely removed with the coexistence of NO_x and SO₂. Interestingly, the effect of SO₂ on NH₃ oxidation was bifacial, and the N₂ selectivity of the resulting products was as high as 100% in the presence of SO₂ and NH₃. The mechanism of the SCO of NH₃ over Ru/Ce_0.6Zr_0.4O₂(PVP) was studied using various techniques, and the results showed that NH₃ oxidation follows an internal SCR (iSCR) mechanism. The adsorbed ammonia was first activated and reacted with lattice oxygen atoms to form an 鈭扝NO intermediate. Then, the 鈭扝NO mainly reacted with atomic oxygen from O₂ to form NO. Meanwhile, the formed NO interacted with 鈭扤H₂ to N₂ with N₂O as the byproduct, but the presence of SO₂ can effectively inhibit the production of N₂O.