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Improvement of Activity and SO₂ Tolerance of Sn-modified MnOx-CeO₂ Catalysts for NH₃-SCR at Low Temperatures

Improvement of Activity and SO₂ Tolerance of Sn-modified MnOx-CeO₂ Catalysts for NH₃-SCR at Low Temperatures

Huazhen Chang, Xiaoyin Chen, Junhua Li, Lei Ma, Chizhong Wang, Caixia Liu, Johannes W Schwank, Jiming Hao

Environ Sci Technol. 2013 May 21;47(10):5294-301.

PMID: 23582170

Abstract:

The performances of fresh and sulfated MnOx-CeO₂ catalysts for selective catalytic reduction of NOx by NH₃ (NH₃-SCR) in a low-temperature range (T < 300 °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% NOx conversion at 110-230 °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 MnOx-CeO₂, Sn-modified MnOx-CeO₂ 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 MnOx-CeO₂ catalyst gave 62% and 94% NOx conversions as compared to 18% and 56% over MnOx-CeO₂ at temperatures of 110 and 220 °C, respectively. Sulfation of SnO₂-modified MnOx-CeO₂ may form Ce(III) sulfate that could enhance the Lewis acidity and improve NO oxidation to NO₂ during NH₃-SCR at T > 200 °C.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP13454949	Cerium(III) sulfate		13454-94-9	Price

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