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<p>We report the effect of the carbon/nitrogen ratio (C/N), from 0 to 26.2, on the activity and selectivity of the NO Selective Catalytic Reduction with propane and hydrogen (H<sub>2</sub>-C<sub>3</sub>H<sub>8</sub>-SCR) over 2 wt% Ag/γ-Al<sub>2</sub>O<sub>3</sub> between 25 and 500&#xa0;°C. The gas composition included 3% (v/v) O<sub>2</sub> and 6% (v/v) H<sub>2</sub>O at GHSV = 70,651&#xa0;h<sup>−1</sup>. There are two NO conversion zones as a function of temperature, previously reported. The low temperature ranged from 60 to 180&#xa0;°C and reached 100% conversion of NO to N<sub>2</sub> at 140&#xa0;°C. The addition of C<sub>3</sub>H<sub>8</sub> had a small effect, decreasing NO conversion to 90–95%, and the temperature window about 10&#xa0;°C. The H<sub>2</sub> conversion increased as a sigmoidal curve with temperature in all cases, and it shifted to low temperature too. This NO reduction range corresponds to the H<sub>2</sub>-SCR. The high temperature activity region involves competition for O<sub>2</sub> between NO and C<sub>3</sub>H<sub>8</sub>. When C/N = 0 there was only oxidation to NO<sub>2</sub>. At C/N = 3.2 and 6.5 there was emission of NO<sub>2</sub> between 160 and 440&#xa0;°C. At higher temperatures the selectivity to N<sub>2</sub> was &gt; 88%. Above C/N = 13.1 the NO conversion reached 90 to 98%. The N<sub>2</sub>O concentration was negligible. The optimum C/N value was 13.1, with high NO conversion at low and high temperatures, and nearly 100% selectivity to N<sub>2</sub>. Analysis by XPS and UV–Vis–NIR showed the coexistence of Ag<sup>+</sup> and Ag<sup>0</sup> moieties that helps explain the variations and competition of the oxidation–reduction reactions of the NO–H<sub>2</sub>–C<sub>3</sub>H<sub>8</sub>–O<sub>2</sub> system with temperature and with the C/N feed values.</p>

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Effect of the Carbon/Nitrogen Ratio on the NO H2-SCR and H2–C3H8-SCR Catalyzed by Ag/γ-Al2O3

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  • 发表日期：

    2025年7月4日

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  • M. E. Hernández-Terán,
  • J. L. García-Gutiérrez,
  • Victor Lara,
  • José Luis Contreras-Larios,
  • G. A. Fuentes

摘要

We report the effect of the carbon/nitrogen ratio (C/N), from 0 to 26.2, on the activity and selectivity of the NO Selective Catalytic Reduction with propane and hydrogen (H2-C3H8-SCR) over 2 wt% Ag/γ-Al2O3 between 25 and 500 °C. The gas composition included 3% (v/v) O2 and 6% (v/v) H2O at GHSV = 70,651 h−1. There are two NO conversion zones as a function of temperature, previously reported. The low temperature ranged from 60 to 180 °C and reached 100% conversion of NO to N2 at 140 °C. The addition of C3H8 had a small effect, decreasing NO conversion to 90–95%, and the temperature window about 10 °C. The H2 conversion increased as a sigmoidal curve with temperature in all cases, and it shifted to low temperature too. This NO reduction range corresponds to the H2-SCR. The high temperature activity region involves competition for O2 between NO and C3H8. When C/N = 0 there was only oxidation to NO2. At C/N = 3.2 and 6.5 there was emission of NO2 between 160 and 440 °C. At higher temperatures the selectivity to N2 was > 88%. Above C/N = 13.1 the NO conversion reached 90 to 98%. The N2O concentration was negligible. The optimum C/N value was 13.1, with high NO conversion at low and high temperatures, and nearly 100% selectivity to N2. Analysis by XPS and UV–Vis–NIR showed the coexistence of Ag+ and Ag0 moieties that helps explain the variations and competition of the oxidation–reduction reactions of the NO–H2–C3H8–O2 system with temperature and with the C/N feed values.