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Difusión dependiente de la temperatura y la carga de hidrocarburos ligeros en ZIF-8 según lo predicho a través de
Ross J Verploegh1, Sankar Nair1, David S Sholl1
1School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States.
Journal of the American Chemical Society
|November 26, 2015
Resumen
Las predicciones precisas de la difusión de hidrocarburos en ZIF-8 se lograron utilizando la teoría del estado de transición corregida dinámicamente (dcTST). Este método tiene en cuenta la flexibilidad del material y modela con éxito la difusión a través de varias cargas y temperaturas de hidrocarburos.
Área de la Ciencia:
- Ciencias de los materiales
- Ingeniería Química
- Química computacional
Sus antecedentes:
- Es difícil predecir con precisión la difusión de hidrocarburos en marcos de imidazolatos zeolíticos (ZIF), particularmente ZIF-8, debido al pequeño tamaño de los poros y a las diversas escalas de tiempo de difusión.
- La comprensión de la difusión es crucial para el diseño de ZIF para aplicaciones de separación y almacenamiento de gases.
Objetivo del estudio:
- Para medir de forma computacional las tasas de salto y predecir las difusividades de hidrocarburos en ZIF-8.
- Investigar el impacto de la flexibilidad ZIF-8 y la carga de hidrocarburos en los coeficientes de difusión.
Principales métodos:
- Se empleó la teoría del estado de transición corregida dinámicamente (dcTST) para calcular las tasas de salto.
- Para determinar las barreras energéticas libres de difusión se utilizó el muestreo general y el método de análisis de histogramas ponderados (WHAM).
- La flexibilidad ZIF-8 se incorporó tanto en el muestreo general como en los cálculos de corrección dinámica.
Principales resultados:
- Las difusividades computarizadas mostraron un acuerdo notable (dentro de un orden de magnitud) con los datos experimentales de 15 moléculas diferentes.
- El estudio modela con éxito la difusión a través de una gama de cargas de hidrocarburos, desde la dilución infinita hasta las condiciones similares a las líquidas.
- Se informaron coeficientes de auto difusión y de transporte para varios hidrocarburos en un rango de temperatura de 0 a 150 °C.
Conclusiones:
- La teoría del estado de transición corregida dinámicamente (dcTST) proporciona predicciones precisas de la difusión de hidrocarburos en ZIF-8.
- Tener en cuenta la flexibilidad de ZIF-8 es fundamental para el modelado preciso de la difusión.
- El método desarrollado es aplicable para estudiar la difusión en condiciones variables, ayudando en el diseño de materiales ZIF.
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