Improved activity and SO₂ tolerance of rare-earth elements modified CeTi catalyst for Hg⁰ and NO simultaneous removal from flue gas

ABSTRACT

Six rare-earth elements (including La, Sm, Pr, Dy, Y, and Nd) were modified on the surface of the CeTi samples for Hg⁰ oxidation and NO oxidation. The X-CeTi catalysts significantly improved the Hg⁰ oxidation, NO oxidation, and SO₂ tolerance compared with the CeTi catalyst. Moreover, O₂ and NO can facilitate the activities significantly. The BET results showed that the specific surface area could be increased by doping of rare-earth elements. In addition, XRD and FT-IR experiments indicated that the rare-earth elements can facilitate the formation of the amorphous structure of CeO₂. The XPS curves of Ce 3d and O 1s showed that surface oxygen species and Ce⁴⁺/Ce³⁺ redox couples were responsible for the catalytic performance, confirming that the SO₂ tolerance was improved via the electron transfer by Ce⁴⁺+Dy²⁺⇌Ce³⁺+Dy³⁺ reactions. The H₂-TPR results suggested that the redox capacity of X-CeTi catalysts was enhanced, which could improve the activities of the catalysts. Moreover, Dy-CeTi had the highest NO and Hg⁰ oxidation among these rare-earth elements on account of the largest specific surface, more surface-active oxygen and H₂-TPR reduction peak integral area. The catalyst can maintain the conversion efficiency of elemental mercury and NO at 67% and 76% even in flue gas containing 800 ppm SO₂. Such work supplied new insights into modified Ce-Ti catalysts to simultaneously remove NO and elemental mercury from the flue gas with high efficiencies, which owned a promising prospect in the practical industrial application.

KEYWORDS:

• Rare-earth elements doping
• Hg⁰ oxidation
• NO conversion
• CeO₂/TiO₂
• SO₂ tolerance

Acknowledgments

The Test Center of Wuhan University is acknowledged for their support of this study.

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