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Hidrógenos a base de titanio como catalizadores heterogéneos para la síntesis de amoníaco

Yoji Kobayashi^1,2, Ya Tang¹, Toki Kageyama¹

¹Department of Energy and Hydrocarbon Chemistry, Kyoto University , Nishikyo-ku, Kyoto 615-8510, Japan.

Journal of the American Chemical Society

|November 23, 2017

Resumen

Los compuestos de hidruro de titanio catalizan la síntesis de amoníaco a partir de nitrógeno e hidrógeno a altas temperaturas. Este descubrimiento amplía la gama de catalizadores de metales no preciosos para la producción de amoníaco.

Área de la Ciencia:

Ciencias de los materiales
Catálisis
Química inorgánica

Sus antecedentes:

La activación del nitrógeno (N2) y la hidrogenación al amoníaco (NH3) son cruciales para la producción mundial de alimentos.
Los complejos de hidruro de metales de transición se exploran para la activación de N2, pero la formación catalítica de NH3 sigue siendo un desafío.
Los complejos de hidruro de titanio (Ti) y tanto (Ta) activan el N2, pero no producen catalíticamente el NH3.

Objetivo del estudio:

Investigar el potencial catalítico de los compuestos de titanio que contienen hidrógeno en estado sólido para la síntesis de amoníaco.
Explorar una nueva vía para la producción de amoníaco utilizando catalizadores de metales no preciosos.

Principales métodos:

Se utilizan compuestos de Ti en estado sólido (TiH2 y BaTiO2.5H0.5) a altas temperaturas (400 °C) y presiones (5 MPa).
Operado en condiciones de flujo continuo de H2/N2 durante períodos prolongados (∼7 días).
Comparación de la actividad catalítica con los catalizadores convencionales de rutenio (Ru).

Principales resultados:

TiH2 y BaTiO2.5H0.5 formaron una superficie de nitruro-hidruro, produciendo continuamente NH3.
Se alcanzó una actividad catalítica de hasta 2,8 mmol·g−1·h−1, comparable a la de algunos catalizadores Ru soportados.
Demostró el papel crítico de la presencia inicial de hidruro para la actividad catalítica.

Conclusiones:

Los compuestos de hidruro de titanio en estado sólido pueden servir como catalizadores efectivos para la síntesis de amoníaco.
El hidruro inicial es esencial, lo que sugiere un mecanismo basado en el hidrógeno de Mars van Krevelen.
La introducción de hidruro en Ti amplía el alcance de los catalizadores heterogéneos, ofreciendo alternativas a los metales preciosos.

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