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Nitration-Promoted Vanadate Catalysts for Low-Temperature Selective Catalytic Reduction of NO_X with NH₃.

ABSTRACT: Vanadium-based catalysts have been commercially used in selective catalytic reduction (SCR), owing to their high catalytic activity and effectiveness across a wide temperature range; however, their catalytic efficiency decreases at lower temperatures under exposure to SO_X. This decrease is largely due to ammonium sulfate generation on the catalyst surface. To overcome this limitation, we added ammonium nitrate to the V₂O₅-WO₃/TiO₂ catalyst, producing a V₂O₅-WO₃/TiO₂ catalyst with nitrate functional groups. With this approach, we found that it was possible to adjust the amount of these functional groups by varying the amount of ammonium nitrate. Overall, the resultant nitrate V₂O₅-WO₃/TiO₂ catalyst has large quantities of NO₃^- and chemisorbed oxygen, which improves the density of Brønsted and Lewis acid sites on the catalyst surface. Furthermore, the nitrated V₂O₅-WO₃/TiO₂ catalyst has a high NO_X removal efficiency and N₂ selectivity at low temperatures (i.e., 300 °C); this is because NO₃^- and chemisorbed oxygen, generated by nitrate treatment, facilitated the occurrence of a fast SCR reaction. The approach outlined in this study can be applied to a wide range of SCR catalysts, allowing for the development of more, low-temperature SCR catalysts.

SUBMITTER: Kim SI

PROVIDER: S-EPMC10515594 | biostudies-literature | 2023 Sep

REPOSITORIES: biostudies-literature

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Nitration-Promoted Vanadate Catalysts for Low-Temperature Selective Catalytic Reduction of NOX with NH3.

Kim Sun-I SI Choi Yeong Jun YJ Lee Min Seong MS Lee Duck Hyun DH

ACS omega 20230906 37

Vanadium-based catalysts have been commercially used in selective catalytic reduction (SCR), owing to their high catalytic activity and effectiveness across a wide temperature range; however, their catalytic efficiency decreases at lower temperatures under exposure to SOX. This decrease is largely due to ammonium sulfate generation on the catalyst surface. To overcome this limitation, we added ammonium nitrate to the V2O5-WO3/TiO2 cat ...[more]

PMID: 37744798

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Project description:In this paper, a series of tungsten-zirconium mixed binary oxides (denoted as W m ZrO x ) were synthesized via co-precipitation as supports to prepare Ce0.4/W m ZrO x catalysts through an impregnation method. The promoting effect of W doping in ZrO2 on selective catalytic reduction (SCR) performance of Ce0.4/ZrO2 catalysts was investigated. The results demonstrated that addition of W in ZrO2 could remarkably enhance the catalytic performance of Ce0.4/ZrO2 catalysts in a broad temperature range. Especially when the W/Zr molar ratio was 0.1, the Ce0.4/W0.1ZrO x catalyst exhibited the widest active temperature window of 226-446 °C (NO x conversion rate > 80%) and its N2 selectivity was almost 100% in the temperature of 150-450 °C. Moreover, the Ce0.4/W0.1ZrO x catalyst also exhibited good SO2 tolerance, which could maintain more than 94% of NO x conversion efficiency after being exposed to a 100 ppm SO2 atmosphere for 18 h. Various characterization results manifested that a proper amount of W doping in ZrO2 was not only beneficial to enlarge the specific surface area of the catalyst, but also inhibited the growth of fluorite structure CeO2, which were in favor of CeO2 dispersion on the support. The presence of W was conducive to the growth of a stable tetragonal phase crystal of ZrO2 support, and a part of W and Zr combined to form W-Zr-O x solid super acid. Both of them resulted in abundant Lewis acid sites and Brønsted acid sites, enhancing the total surface acidity, thus significantly improving NH3 species adsorption on the surface of the Ce0.4/W0.1ZrO x catalyst. Furthermore, the promoting effect of adding W on SCR performance was also related to the improved redox capability, higher Ce3+/(Ce3+ + Ce4+) ratio and abundant surface chemisorbed oxygen species. The in situ DRIFTS results indicated that nitrate species adsorbed on the surface of the Ce0.4/W0.1ZrO x catalyst could react with NH3 due to the activation of W. Therefore, the reaction pathway over the Ce0.4/W0.1ZrO x catalyst followed both Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanisms at 250 °C.

Dataset Information

Nitration-Promoted Vanadate Catalysts for Low-Temperature Selective Catalytic Reduction of NO_X with NH₃.

Publications

Nitration-Promoted Vanadate Catalysts for Low-Temperature Selective Catalytic Reduction of NO<sub><i>X</i></sub> with NH<sub>3</sub>.

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