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Naturaleza del hidrógeno reactivo para la síntesis de amoníaco sobre un catalizador de electruro de Ru/C12A7
James Kammert1, Jisue Moon1,2, Yongqiang Cheng3
1Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Journal of the American Chemical Society
|April 7, 2020
Resumen
El hidrógeno adsorbido en la superficie, no el hidruro encapsulado, es clave para la síntesis de amoníaco sobre catalizadores de electruros. Los soportes de electruros mejoran la cobertura intermedia reactiva, mejorando la eficiencia de la producción de amoníaco.
Área de la Ciencia:
- Ciencias de la catálisis
- Ciencias de los materiales
- Química de las superficies
Sus antecedentes:
- Nuevo interés por los catalizadores para la síntesis de amoníaco en condiciones suaves.
- Los catalizadores basados en electridos, específicamente el rutenio sobre el óxido de calcio y aluminio (Ru/C12A7), son prometedores para la activación de N2.
- El papel preciso del soporte de electridos y las especies reactivas de hidrógeno en la catálisis de Ru/C12A7 sigue sin estar claro.
Objetivo del estudio:
- Para aclarar el papel de las especies de hidrógeno y el soporte de electridos en la síntesis de amoníaco sobre Ru/C12A7.
- Para proporcionar evidencia directa de la naturaleza del hidrógeno activo y la función del electrido.
Principales métodos:
- Técnicas de dispersión de neutrones in situ (difracción de neutrones, espectroscopia inelástica de neutrones).
- Cálculos de la teoría funcional de la densidad (DFT).
- Las reacciones programadas por temperatura y el análisis cinético transitorio isotópico en estado estacionario (SSITKA).
Principales resultados:
- El hidrógeno adsorbido en la superficie, no el hidruro enjaulado, se identifica como la especie reactiva primaria para la síntesis de amoníaco.
- Las especies de hidruro encerradas dentro de C12A7 son térmicamente y químicamente estables.
- El soporte de electridos mejora significativamente la cobertura reactiva intermedia de Ru (hasta el 84%) en comparación con la forma de óxido (15%), mitigando el envenenamiento por H2.
Conclusiones:
- Las especies de hidrógeno de superficie son cruciales para la síntesis de amoníaco sobre los catalizadores de electruros Ru/C12A7.
- La forma de electrido de C12A7 juega un papel vital en la promoción de la catálisis mediante el aumento de la cobertura intermedia y la prevención del envenenamiento por catalizador.
- Los hallazgos avanzan en la comprensión de la catálisis basada en electruros para la síntesis de amoníaco y las reacciones de hidrogenación.
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