Abstract
AbstractBACKGROUNDSelective catalytic reduction (SCR) of nitrous oxides (NOx) with ammonia (NH3) as reductant is used worldwide in mobile and stationary sources to reach strict emission standards. It is a feasible strategy to modify support with acidic metal oxides to improve the alkali metal potassium (K) tolerance of SCR catalysts. Herein, a comparative investigation was conducted based on iron/zirconium dioxide (Fe/ZrO2)and Fe/ZrO2‐tungsten (W) catalysts to reveal the correlation of support modification with W and K‐tolerance performance.RESULTSThe NOx conversion for K‐Fe/ZrO2 catalyst was <80% across the whole temperature range, and the catalyst was completely deactivated at ≈400 °C. As expected, the Fe/ZrO2‐W catalyst exhibited a much superior anti‐K‐performance in comparison to the Fe/ZrO2 catalyst. The active temperature window for K‐Fe/ZrO2‐W catalyst was 285–485 °C (NOx conversion of >80%).CONCLUSIONAccording to the characterization results, it was found that K‐species impose a negative impact on NH3 adsorption on the surface of the Fe/ZrO2 catalyst, especially drastically preventing the adsorption of NH3 species on Brønsted acid sites, thus inhibiting the occurrence of SCR reactions via the Langmuir–Hinshelwood (L‐H) mechanism. By contrast, W modification resulted in more chemisorbed oxygen, stronger redox capacity and an increased Fe3+/(Fe3++Fe2+) ratio on the surface of the Fe/ZrO2‐W catalyst. More importantly, W modification brought about abundant Brønsted acid sites, significantly promoting NH3 adsorption and activation. W modification also weakened the adsorption stability of NOx species to a certain extent. As a result, SCR reactions over the Fe/ZrO2‐W catalyst could proceed via both Eley–Rideal (E‐R) and L‐H pathways. © 2023 Society of Chemical Industry (SCI).
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