Progress on Noble Metal-Based Catalysts Dedicated to the Selective Catalytic Ammonia Oxidation into Nitrogen and Water Vapor (NH<sub>3</sub>-SCO)
A recent development for selective ammonia oxidation into nitrogen and water vapor (NH<sub>3</sub>-SCO) over noble metal-based catalysts is covered in the mini-review. As ammonia (NH<sub>3</sub>) can harm human health and the environment, it led to stringent regulations by en...
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| Formato: | article |
| Lenguaje: | EN |
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MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/172104282c4b4beca3c0cc4586f5aa5b |
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| Sumario: | A recent development for selective ammonia oxidation into nitrogen and water vapor (NH<sub>3</sub>-SCO) over noble metal-based catalysts is covered in the mini-review. As ammonia (NH<sub>3</sub>) can harm human health and the environment, it led to stringent regulations by environmental agencies around the world. With the enforcement of the Euro VI emission standards, in which a limitation for NH<sub>3</sub> emissions is proposed, NH<sub>3</sub> emissions are becoming more and more of a concern. Noble metal-based catalysts (i.e., in the metallic form, noble metals supported on metal oxides or ion-exchanged zeolites, etc.) were rapidly found to possess high catalytic activity for NH<sub>3</sub> oxidation at low temperatures. Thus, a comprehensive discussion of property-activity correlations of the noble-based catalysts, including Pt-, Pd-, Ag- and Au-, Ru-based catalysts is given. Furthermore, due to the relatively narrow operating temperature window of full NH<sub>3</sub> conversion, high selectivity to N<sub>2</sub>O and NO<sub><i>x</i></sub> as well as high costs of noble metal-based catalysts, recent developments are aimed at combining the advantages of noble metals and transition metals. Thus, also a brief overview is provided about the design of the bifunctional catalysts (i.e., as dual-layer catalysts, mixed form (mechanical mixture), hybrid catalysts having dual-layer and mixed catalysts, core-shell structure, etc.). Finally, the general conclusions together with a discussion of promising research directions are provided. |
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