Consistent adsorption characterization of nanoporous materials is imperative for their wider adop... more Consistent adsorption characterization of nanoporous materials is imperative for their wider adoption in industry and practical applications. This dissertation considers the current techniques for characterization of nanoporous materials using gas adsorption and proposes new methodologies to advance the field. This is achieved by the extensive use of modeling procedures and the validation against experimental data provided by Prof. Matthias Thommes' lab and data available in the literature. Strategic application of Monte Carlo methods and other computational schemes provided critical information about the systems considered in this work. First, the influence of temperature on CO2 adsorption focusing on the capillary condensation and hysteresis phenomena is investigated. This study led to the creation of an original methodology for evaluating the pore size distribution in carbons in a wide range of micro- and mesopores from 0.385 to 10 nm from a single isotherm of high-pressure a...
Abstract We presented a new kernel of heterogenous carbon surfaces constructed using the reactive... more Abstract We presented a new kernel of heterogenous carbon surfaces constructed using the reactive molecular dynamics model (rMD). The rMD model explicitly incorporates edges and corrugations resulting from the oxidative etching of graphene walls. The rMD model eliminates the computational artifacts characteristic to the homogeneous pore wall models. In ultramicropores, early uptake is guided by the competition between central energetic adsorption sites and heterogeneities of the wall. In the larger pores, the central energy diminishes and the preferential adsorption sites are located in the pore wall. Comparisons between the rMD model, which mimics the surface roughness explicitly, and the quenched solid density functional theory (QSDFT) model are performed. The rMD model performs similarly to the QSDFT in the reproduction of the carbon experimental isotherms, indicating that it is a viable alternative to the implicit models for carbon characterization. In calculated PSDs, the rMD model attributes higher volumes to the ultramicropores than the QSDFT model due to enhanced adsorption on the surface defects. Finally, we tested the influence of the N2 molecular probe models on adsorption isotherms. It is found that the discrepancies between the nitrogen probe models on heterogeneous wall surfaces are smaller than those for the homogeneous models.
Anais do XX Congresso Brasileiro de Engenharia Química, 2015
RESUMO-Carbono ativado é um adsorvente amplamente usado para purificação de diversas correntes na... more RESUMO-Carbono ativado é um adsorvente amplamente usado para purificação de diversas correntes na indústria petroquímica, porém sua estrutura amorfa dificulta a elaboração de modelos apropriados. Este trabalho foi realizado com o intuito de propor modelos computacionais para sistemas de adsorção contendo compostos aromáticos sulfurados e carbono ativado. Foram utilizados três poros típicos das distribuições de poros encontrados em carbonos ativados (8,9 Å, 18,5 Å e 30,9 Å). Para os adsorbatos, foram propostos novos parâmetros para modelar as moléculas de benzotiofeno e de dibenzotiofeno. Simulações foram realizadas utilizando o método computacional de Monte Carlo. Isotermas de adsorção foram geradas à 393 e 453 K, estas mostram que, para o poro menor, a adsorção ocorre em baixas pressões quando comparada com as isotermas dos poros maiores. O poro de 18,5 Å apresentou a melhor relação entre quantidade adsorvida e calor de adsorção. Considerações sobre a distribuição de poros mais eficiente para a captura de aromáticos sulfurados são também apresentadas.
Consistent adsorption characterization of nanoporous materials is imperative for their wider adop... more Consistent adsorption characterization of nanoporous materials is imperative for their wider adoption in industry and practical applications. This dissertation considers the current techniques for characterization of nanoporous materials using gas adsorption and proposes new methodologies to advance the field. This is achieved by the extensive use of modeling procedures and the validation against experimental data provided by Prof. Matthias Thommes' lab and data available in the literature. Strategic application of Monte Carlo methods and other computational schemes provided critical information about the systems considered in this work. First, the influence of temperature on CO2 adsorption focusing on the capillary condensation and hysteresis phenomena is investigated. This study led to the creation of an original methodology for evaluating the pore size distribution in carbons in a wide range of micro- and mesopores from 0.385 to 10 nm from a single isotherm of high-pressure a...
Abstract We presented a new kernel of heterogenous carbon surfaces constructed using the reactive... more Abstract We presented a new kernel of heterogenous carbon surfaces constructed using the reactive molecular dynamics model (rMD). The rMD model explicitly incorporates edges and corrugations resulting from the oxidative etching of graphene walls. The rMD model eliminates the computational artifacts characteristic to the homogeneous pore wall models. In ultramicropores, early uptake is guided by the competition between central energetic adsorption sites and heterogeneities of the wall. In the larger pores, the central energy diminishes and the preferential adsorption sites are located in the pore wall. Comparisons between the rMD model, which mimics the surface roughness explicitly, and the quenched solid density functional theory (QSDFT) model are performed. The rMD model performs similarly to the QSDFT in the reproduction of the carbon experimental isotherms, indicating that it is a viable alternative to the implicit models for carbon characterization. In calculated PSDs, the rMD model attributes higher volumes to the ultramicropores than the QSDFT model due to enhanced adsorption on the surface defects. Finally, we tested the influence of the N2 molecular probe models on adsorption isotherms. It is found that the discrepancies between the nitrogen probe models on heterogeneous wall surfaces are smaller than those for the homogeneous models.
Anais do XX Congresso Brasileiro de Engenharia Química, 2015
RESUMO-Carbono ativado é um adsorvente amplamente usado para purificação de diversas correntes na... more RESUMO-Carbono ativado é um adsorvente amplamente usado para purificação de diversas correntes na indústria petroquímica, porém sua estrutura amorfa dificulta a elaboração de modelos apropriados. Este trabalho foi realizado com o intuito de propor modelos computacionais para sistemas de adsorção contendo compostos aromáticos sulfurados e carbono ativado. Foram utilizados três poros típicos das distribuições de poros encontrados em carbonos ativados (8,9 Å, 18,5 Å e 30,9 Å). Para os adsorbatos, foram propostos novos parâmetros para modelar as moléculas de benzotiofeno e de dibenzotiofeno. Simulações foram realizadas utilizando o método computacional de Monte Carlo. Isotermas de adsorção foram geradas à 393 e 453 K, estas mostram que, para o poro menor, a adsorção ocorre em baixas pressões quando comparada com as isotermas dos poros maiores. O poro de 18,5 Å apresentou a melhor relação entre quantidade adsorvida e calor de adsorção. Considerações sobre a distribuição de poros mais eficiente para a captura de aromáticos sulfurados são também apresentadas.
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