Almacenamiento de hidrógeno en carbón activado obtenido de carbón mineral. Efecto de la adición de Ni y Cu como promotores metálicos.
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Date
2023
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Universidad de Concepción.
Abstract
El hidrógeno emerge como una opción altamente prometedora ante los apremiantes problemas climáticos. Sin embargo, surge una complicación central relacionada con su almacenamiento, ya que las formas convencionales presentan diversas limitaciones. Recientemente, la investigación científica se ha focalizado en el almacenamiento mediante materiales sólidos, específicamente en el carbón activado. Además, se sugiere que la introducción de metales podría ser una estrategia beneficiosa para mejorar este proceso de almacenamiento. En este contexto, se llevó a cabo un estudio para investigar cómo la adición de Ni y Cu en un carbón activado derivado de carbón mineral activado químicamente con NaOH, influye en el almacenamiento de hidrógeno. Los carbones activados fueron dopados con diferentes niveles de carga de metal: 0,5%, 1,0%, 1,5%, 2,5% y 5,0% en masa. Para caracterizar los carbones preparados, se realizaron pruebas de adsorción de nitrógeno a 77 K, con el fin de determinar parámetros cruciales como el área superficial BET y el volumen de microporos. Así mismo, se efectuaron pruebas de adsorción de hidrógeno a 77 K y 1 bar. Además, se aplicaron otros análisis con el propósito de obtener información adicional. Estos incluyen análisis elemental e inmediato, TEM y un análisis teórico aplicando el modelo de adsorción de Dubinin-Astakhov [56]. Los resultados demostraron que los carbones dopados, tanto con Ni y Cu presentaron una mayor porosidad en comparación al carbón sin dopar, lo cual se traduce en una mayor área BET. La forma de las isotermas de adsorción de nitrógeno de las muestras dopadas no presentó ninguna variación respecto de los carbones base, salvo en el caso del 5 Ni-CA, las isotermas fueron de tipo I y tipo IV según los criterios de la IUPAC. Se comprobó además una relación lineal entre el área BET y el volumen de microporos. El análisis TEM proporcionó un rango de tamaño de partícula que varió entre 14-7 nm, destacando que la muestra 2,5 Cu-CA exhibió este último valor. Con respecto a la adsorción de hidrógeno, se plantea la posibilidad de que la introducción de metal tenga un impacto restringido a condiciones de 77 K y 1 bar, lo cual podría estar influenciado por taponamiento de los poros. Esto se evidencia en el hecho de que la muestra de mayor desempeño fue 1,5-Ni-CA, alcanzando un valor del 2,51 % en peso de H2, lo que representa un aumento de solo un 1,6 % en comparación con la muestra sin dopar. Finalmente se logró proyectar los datos experimentales del carbón activado a condiciones de elevadas presiones y diversas temperaturas. Como resultado, se obtuvo un valor de 8,74% en peso a 100 bar, mientras que se registró un valor de 0,69% en peso a 298 K y 100 bar.
Hydrogen is emerging as a highly promising option in the face of pressing climate issues. However, a central complication arises related to its storage, since conventional forms present various limitations. Recently, scientific research has focused on storage using solid materials, specifically activated carbon. In addition, it is suggested that the introduction of metals could be a beneficial strategy to improve this storage process. In this context, a study was conducted to investigate how the addition of Ni and Cu in an activated carbon derived from chemically activated mineral carbon with NaOH, influences hydrogen storage. The activated carbons were doped with different levels of metal charge: 0,5%, 1,0%, 1,5%, 2,5% and 5,0% by mass. To characterize the prepared carbons, nitrogen adsorption tests were performed at 77 K, in order to determine crucial parameters such as BET surface area and micropore volume. Likewise, hydrogen adsorption tests were carried out at 77 K and 1 bar. In addition, other analyses were applied in order to obtain additional information. These include elemental and immediate analysis, TEM and a theoretical analysis applying the Dubinin-Astakhov adsorption model [56]. The results showed that doped carbons with both Ni and Cu presented a higher porosity compared to undoped carbon, which translates into a greater BET area. The shape of the nitrogen adsorption isotherms of the doped samples did not present any variation with respect to the base carbons, except in the case of 5 Ni-CA, the isotherms were type I and type IV according to IUPAC criteria. A linear relationship between the BET area and the volume of micropores was also verified. The TEM analysis provided a particle size range that varied between 14-7 nm, highlighting that the 2,5 Cu-CA sample exhibited this last value. With regard to hydrogen adsorption, the possibility arises that the introduction of metal has an impact restricted to conditions of 77 K and 1 bar, which could be influenced by clogging of the pores. This is evidenced by the fact that the highest performing sample was 1,5-Ni-CA, reaching a value of 2,51% by weight of H2, representing an increase of only 1,6% compared to the undoped sample. Finally, it was possible to project the experimental data of activated carbon at conditions of high pressures and different temperatures. As a result, a value of 8,74% by weight was obtained at 100 bar, while a value of 0,69% by weight was recorded at 298 K and 100 bar.
Hydrogen is emerging as a highly promising option in the face of pressing climate issues. However, a central complication arises related to its storage, since conventional forms present various limitations. Recently, scientific research has focused on storage using solid materials, specifically activated carbon. In addition, it is suggested that the introduction of metals could be a beneficial strategy to improve this storage process. In this context, a study was conducted to investigate how the addition of Ni and Cu in an activated carbon derived from chemically activated mineral carbon with NaOH, influences hydrogen storage. The activated carbons were doped with different levels of metal charge: 0,5%, 1,0%, 1,5%, 2,5% and 5,0% by mass. To characterize the prepared carbons, nitrogen adsorption tests were performed at 77 K, in order to determine crucial parameters such as BET surface area and micropore volume. Likewise, hydrogen adsorption tests were carried out at 77 K and 1 bar. In addition, other analyses were applied in order to obtain additional information. These include elemental and immediate analysis, TEM and a theoretical analysis applying the Dubinin-Astakhov adsorption model [56]. The results showed that doped carbons with both Ni and Cu presented a higher porosity compared to undoped carbon, which translates into a greater BET area. The shape of the nitrogen adsorption isotherms of the doped samples did not present any variation with respect to the base carbons, except in the case of 5 Ni-CA, the isotherms were type I and type IV according to IUPAC criteria. A linear relationship between the BET area and the volume of micropores was also verified. The TEM analysis provided a particle size range that varied between 14-7 nm, highlighting that the 2,5 Cu-CA sample exhibited this last value. With regard to hydrogen adsorption, the possibility arises that the introduction of metal has an impact restricted to conditions of 77 K and 1 bar, which could be influenced by clogging of the pores. This is evidenced by the fact that the highest performing sample was 1,5-Ni-CA, reaching a value of 2,51% by weight of H2, representing an increase of only 1,6% compared to the undoped sample. Finally, it was possible to project the experimental data of activated carbon at conditions of high pressures and different temperatures. As a result, a value of 8,74% by weight was obtained at 100 bar, while a value of 0,69% by weight was recorded at 298 K and 100 bar.
Description
Tesis presentada para optar al título profesional de Ingeniero Civil Químico.