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Reactividad de la interfaz oro/agua durante la catálisis de oxidación selectiva
Bhushan N Zope1, David D Hibbitts, Matthew Neurock
1Department of Chemical Engineering, University of Virginia, 102 Engineers' Way, Post Office Box 400741, Charlottesville, VA 22904-4741, USA.
Science (New York, N.Y.)
|October 9, 2010
Resumen
Las condiciones de alto pH ayudan a la oxidación del alcohol sobre los catalizadores de oro y platino soportados. Los iones de hidróxido, no el oxígeno molecular, incorporan átomos de oxígeno a los alcoholes durante este proceso de oxidación selectiva.
Área de la Ciencia:
- La catálisis de la catálisis.
- Las reacciones de oxidación son reacciones de oxidación.
- Química verde es la química verde.
Sus antecedentes:
- La oxidación selectiva de los alcoholes es crucial para la producción de sustancias químicas valiosas.
- La oxidación de la fase acuosa bajo un pH alto es un enfoque emergente de la química verde.
- La comprensión de los mecanismos de reacción es clave para el desarrollo de catalizadores.
Objetivo del estudio:
- Para aclarar el mecanismo de oxidación del etanol y el glicerol a ácidos.
- Para investigar el papel de los iones de hidróxido y el oxígeno molecular en la reacción.
- Para comparar el rendimiento de los catalizadores de oro y platino soportados.
Principales métodos:
- Los catalizadores de oro y platino soportados fueron sintetizados y caracterizados.
- Las reacciones de oxidación de alcohol se llevaron a cabo en fase acuosa bajo un pH alto.
- Se realizaron experimentos de etiquetado isotópico utilizando (18) O ((2)) y H ((2) ((18) O.
- Los cálculos de la teoría funcional de la densidad (DFT) se emplearon para modelar las vías de reacción.
Principales resultados:
- Los experimentos de etiquetado confirmaron la incorporación de oxígeno de los iones de hidróxido en los productos oxidados.
- Los cálculos de DFT revelaron un mecanismo de reacción que involucra tanto pasos mediados por solución como catalizados por metal.
- El papel del oxígeno molecular se identificó como la regeneración de iones de hidróxido, no la transferencia directa de átomos de oxígeno.
Conclusiones:
- El estudio aclara el mecanismo de la oxidación de alcohol en fase acuosa sobre catalizadores metálicos soportados.
- Los iones de hidróxido son la principal fuente de oxígeno incorporado en los productos alcohólicos.
- Se propone un nuevo ciclo catalítico en el que el oxígeno molecular regenera las especies activas de hidróxido.
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