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El catalizador Cu-CHA de NOx en acción: reducción catalítica selectiva asistida por NH3 dependiente de la temperatura
Kirill A Lomachenko1,2, Elisa Borfecchia1, Chiara Negri1
1Department of Chemistry, NIS Centre and INSTM Reference Center, University of Turin , via P. Giuria 7, 10125 Turin, Italy.
Journal of the American Chemical Society
|August 18, 2016
Resumen
Este estudio revela dos comportamientos distintos de los sitios activos de cobre en la zeolita Cu-CHA durante la reducción catalítica selectiva del amoníaco (NH3-SCR). Las especies móviles de cobre dominan las bajas temperaturas, mientras que los sitios de cobre coordinados por el marco impulsan el NH3-SCR de alta temperatura.
Área de la Ciencia:
- Catálisis
- Ciencias de los materiales
- Química del medio ambiente
Sus antecedentes:
- La zeolita Cu-CHA de pequeños poros muestra un alto rendimiento en la reducción catalítica selectiva de NH3 (SCR) para la eliminación de óxido de nitrógeno.
- La comprensión del mecanismo SCR y los sitios activos de cobre es crucial para optimizar el diseño del catalizador.
Objetivo del estudio:
- Para investigar el comportamiento a escala atómica de los sitios activos de Cu en Cu-CHA durante NH3-SCR.
- Para correlacionar la especiación y la movilidad del cobre con la actividad catalítica a través de un rango de temperatura.
Principales métodos:
- Se emplearon espectroscopias de absorción de rayos X operando (XANES, EXAFS) y espectroscopia de emisión de rayos X (XES).
- Monitoreo in situ del catalizador Cu-CHA durante el NH3-SCR entre 150 y 400 °C.
Principales resultados:
- Se identificaron dos regímenes distintos de comportamiento del sitio activo de Cu basados en la temperatura.
- A bajas temperaturas (<200 °C), prevalecen las especies móviles de Cu (I) / Cu (II) solvadas en NH3.
- A altas temperaturas (> 250 °C), los sitios Cu ((II) coordinados por el marco se vuelven dominantes, correlacionándose con una mayor actividad catalítica.
Conclusiones:
- El estudio aclara la evolución dependiente de la temperatura de los sitios activos de cobre en Cu-CHA durante el NH3-SCR.
- Las especies móviles de cobre son activas a temperaturas más bajas, mientras que los sitios de Cu ((II) coordinados por el marco son clave para el rendimiento de SCR a alta temperatura.
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