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<p>Copper-based catalysts are extensively employed in selective catalytic oxidation of ammonia (NH<sub>3</sub>-SCO). Nevertheless, their poor low-temperature activity remains a significant challenge. In this work, a series of Cu<sub><i>a</i></sub>-Ce<sub><i>b</i></sub>/TiO<sub>2</sub> catalysts with different Cu/Ce molar ratios were synthesized via a co-impregnation method. Among them, Cu<sub>1</sub>-Ce<sub>3</sub>/TiO<sub>2</sub> catalyst exhibited excellent low-temperature activity, reducing the T<sub>90</sub> by 24&#xa0;°C compared to Cu/TiO<sub>2</sub> catalyst. In addition, the N<sub>2</sub> selectivity did not decline. Compared to Cu/TiO<sub>2</sub> catalyst, the proportion of adsorbed oxygen on Cu<sub><i>a</i></sub>-Ce<sub><i>b</i></sub>/TiO<sub>2</sub> catalyst surface significantly increased, which was attributed to the presence of Ce<sup>3+</sup> promoting the formation of oxygen vacancies on catalyst surface. Meanwhile, the reduction temperature of Cu species decreased significantly under the interaction of Cu and Ce species, which favored to the catalytic activity. Moreover, Ce species could serve as SCR active sites, which could reduce NO formed by the partial overoxidation of NH<sub>3</sub>, and thus the catalytic activity was enhanced through the synergistic effect of Cu and Ce species, while the decrease of N<sub>2</sub> selectivity was effectively suppressed. With increasing Cu loading, the specific surface area of the catalyst gradually decreased, while the reduction temperature of surface larger CuO particles increased, which might have been attributed to a weakened interaction between Cu and Ce species. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTS) results showed that, in NH<sub>3</sub>-SCO reaction, Ce/TiO<sub>2</sub> catalyst followed the internal selective catalytic reduction (i-SCR) mechanism, while Cu<sub>1</sub>-Ce<sub>3</sub>/TiO<sub>2</sub> followed both i-SCR and amide (-NH) mechanisms.</p> Graphical Abstract <p></p>

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Synthesis of Cu-Ce/TiO2 Catalysts for Highly Efficient Selective Catalytic Oxidation of NH3

  • 期刊论文

  • 发表日期：

    2025年6月17日

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  • Yong Lu,
  • You Tian,
  • Hongzhe Zhao,
  • Zhitao Han

摘要

Copper-based catalysts are extensively employed in selective catalytic oxidation of ammonia (NH3-SCO). Nevertheless, their poor low-temperature activity remains a significant challenge. In this work, a series of Cua-Ceb/TiO2 catalysts with different Cu/Ce molar ratios were synthesized via a co-impregnation method. Among them, Cu1-Ce3/TiO2 catalyst exhibited excellent low-temperature activity, reducing the T90 by 24 °C compared to Cu/TiO2 catalyst. In addition, the N2 selectivity did not decline. Compared to Cu/TiO2 catalyst, the proportion of adsorbed oxygen on Cua-Ceb/TiO2 catalyst surface significantly increased, which was attributed to the presence of Ce3+ promoting the formation of oxygen vacancies on catalyst surface. Meanwhile, the reduction temperature of Cu species decreased significantly under the interaction of Cu and Ce species, which favored to the catalytic activity. Moreover, Ce species could serve as SCR active sites, which could reduce NO formed by the partial overoxidation of NH3, and thus the catalytic activity was enhanced through the synergistic effect of Cu and Ce species, while the decrease of N2 selectivity was effectively suppressed. With increasing Cu loading, the specific surface area of the catalyst gradually decreased, while the reduction temperature of surface larger CuO particles increased, which might have been attributed to a weakened interaction between Cu and Ce species. In situ Diffuse Reflectance Infrared Fourier Transform Spectroscopy (In-situ DRIFTS) results showed that, in NH3-SCO reaction, Ce/TiO2 catalyst followed the internal selective catalytic reduction (i-SCR) mechanism, while Cu1-Ce3/TiO2 followed both i-SCR and amide (-NH) mechanisms.

Graphical Abstract