Improvement of Activity and SO2 Tolerance of Sn-Modified MnOx鈥揅eO2 Catalysts for NH3-SCR at Low Temperatures

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• 作者：Huazhen Chang ; Xiaoyin Chen ; Junhua Li ; Lei Ma ; Chizhong Wang ; Caixia Liu ; Johannes W. Schwank ; Jiming Hao
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：May 21, 2013
• 年：2013
• 卷：47
• 期：10
• 页码：5294-5301
• 全文大小：466K
• 年卷期：v.47,no.10(May 21, 2013)
• ISSN：1520-5851

文摘

The performances of fresh and sulfated MnO_x鈥揅eO₂ catalysts for selective catalytic reduction of NO_x by NH₃ (NH₃-SCR) in a low-temperature range (T < 300 掳C) were investigated. Characterization of these catalysts aimed at elucidating the role of additive and the effect of sulfation. The catalyst having a Sn:Mn:Ce = 1:4:5 molar ratio showed the widest SCR activity improvement with near 100% NO_x conversion at 110鈥?30 掳C. Raman and X-ray photoelectron spectroscopy (XPS) indicated that Sn modification significantly increases the concentration of oxygen vacancies that may facilitate NO oxidation to NO₂. NH₃-TPD characterization showed that the low-temperature NH₃-SCR activity is well correlated with surface acidity for NH₃ adsorption, which is also enhanced by Sn modification. Furthermore, as compared to MnO_x鈥揅eO₂, Sn-modified MnO_x鈥揅eO₂ showed remarkably improved tolerance to SO₂ sulfation and to the combined effect of SO₂ and H₂O. In the presence of SO₂ and H₂O, the Sn-modified MnO_x鈥揅eO₂ catalyst gave 62% and 94% NO_x conversions as compared to 18% and 56% over MnO_x鈥揅eO₂ at temperatures of 110 and 220 掳C, respectively. Sulfation of SnO₂-modified MnO_x鈥揅eO₂ may form Ce(III) sulfate that could enhance the Lewis acidity and improve NO oxidation to NO₂ during NH₃-SCR at T > 200 掳C.