On the prediction of thermodynamic and structural properties in systems of deep eutectic solvents by molecular modeling techniques.
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Date
2025
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Universidad de Concepción
Abstract
La creciente demanda por alternativas sostenibles a los disolventes orgánicos convencionales ha incrementado el interés en los deep eutectic solvents (DES) debido a su baja toxicidad, biodegrad abilidad y propiedades ajustables. Sin embargo, la comprensión integral de su comportamiento termodinámico y estructural —especialmente en presencia de cosolventes, aún es limitada. Esta tesis aborda esto mediante la integración de ecuaciones de estado de base molecular y simula ciones moleculares para predecir y analizar las propiedades de equilibrio de fases y de interfase de DESderivados de precursores verdes como cloruro de colina, betaína, glicoles y terpenos.
Se evaluaron las capacidades predictivas de la ecuación de estado PC-SAFT para una amplia gama de mezclas de DES, evidenciando las limitaciones del enfoque tradicional de componente pseudo puro en sistemas donde ocurre una fuerte asociación cruzada con alcoholes. Se encontró que una estrategia de modelado basadaenloscomponentesindividualespermiteunamejorrepresentación delaspropiedadestermodinámicasenexcesoydelosequilibriosdefases. Además,seimplementó una nueva formulación de la teoría del gradiente de densidad (DGT) combinada con PC-SAFT para describir la tensión superficial utilizando únicamente un parámetro ajustado, lo que permitió analizar esta propiedad y el efecto del cosolvente.
Las simulaciones de dinámica molecular (MD) se emplearon para obtener información a nivel molecular sobre los efectos del agua y de alcoholes de cadena corta en la estructura y propiedades de DES hidrofílicos. Estas simulaciones revelaron la competencia entre interacciones por enlaces de hidrógeno, dando lugar a una reorganización estructural del DES provocando cambios en den sidad, viscosidad y tensión superficial. Paralelamente, se generaron datos experimentales origi nales para una serie de DES hidrofílicos, lo que permitió validar las predicciones teóricas y cubrir vacíos en la literatura, especialmente respecto al efecto del contenido de agua.
Adicionalmente, el estudio se extendió a DES hidrofóbicos basados en mentol, timol y ácido oc tanoico para la extracción de alcohol furfurílico desde agua. Se midieron por primera vez datos de equilibrio líquido-líquido para estos sistemas. Tanto PC-SAFT como simulaciones de MD con modelos coarse-grained predijeron con éxito el comportamiento de fases, demostrando el poten cial del marco propuesto para el diseño de procesos de separación basados en DES.
En conjunto, este trabajo contribuye al avance de modelos termodinámicos predictivos aplicados a DES, ofreciendo herramientas para el diseño racional de disolventes sostenibles con aplicaciones industriales y medioambientales, en apoyo a una química más verde.
The growing demand for sustainable alternatives to conventional organic solvents has increased interest in deep eutectic solvents (DESs) due to their low toxicity, biodegradability, and tunable properties. However, a comprehensive understanding of their thermodynamic and structural be havior—especially in the presence of cosolvents—remains incomplete. This thesis addresses this gap by integrating molecular-based equations of state and molecular simulations to predict and analyze the bulk and interfacial properties of DESs derived from green precursors such as choline chloride, betaine, glycols, and terpenes. The predictive capabilities of the PC-SAFT equation of state were evaluated for a wide range of DES mixtures, revealing the limitations of traditional pseudo-pure component approaches in sys tems where strong cross-association with alcohols occurs. An individual component modeling strategy was found to better capture excess thermodynamic properties and phase equilibria. A novel implementation of density gradient theory (DGT) combined with PC-SAFT was also devel oped to describe surface tension using only a single fitted parameter, enabling the analysis of DES surface tension and how it is affected by cosolvent addition. Molecular dynamics (MD) simulations were employed to provide molecular-level insights into the effects of water and short-chain alcohols on the structure and properties of hydrophilic DESs. These simulations revealed competition among hydrogen-bonding interactions, leading to a reor ganization of the DES structure and changes in density, viscosity, and surface tension. In parallel, original experimental data were generated for a series of hydrophilic DESs, providing critical vali dation for the theoretical predictions and filling gaps in the existing literature, particularly regard ing the effect of water. Additionally, the study was extended to hydrophobic DESs based on menthol, thymol, and oc tanoic acid for the extraction of furfuryl alcohol from water. Liquid–liquid equilibrium (LLE) data for these systems were measured for the first time. Both PC-SAFT and coarse-grained MD simu lations (MARTINI 3) successfully predicted the phase behavior, demonstrating the potential of the proposed framework for the design of DES-based separation processes. Integrating these molecular modeling techniques advances the predictive capabilities of thermo dynamic models for DESs, offering valuable insights for the rational design and optimization of sustainable solvent systems. These advancements contribute to the development of DES formu lations tailored for industrial and environmental applications, supporting the transition toward greener chemical processes.
The growing demand for sustainable alternatives to conventional organic solvents has increased interest in deep eutectic solvents (DESs) due to their low toxicity, biodegradability, and tunable properties. However, a comprehensive understanding of their thermodynamic and structural be havior—especially in the presence of cosolvents—remains incomplete. This thesis addresses this gap by integrating molecular-based equations of state and molecular simulations to predict and analyze the bulk and interfacial properties of DESs derived from green precursors such as choline chloride, betaine, glycols, and terpenes. The predictive capabilities of the PC-SAFT equation of state were evaluated for a wide range of DES mixtures, revealing the limitations of traditional pseudo-pure component approaches in sys tems where strong cross-association with alcohols occurs. An individual component modeling strategy was found to better capture excess thermodynamic properties and phase equilibria. A novel implementation of density gradient theory (DGT) combined with PC-SAFT was also devel oped to describe surface tension using only a single fitted parameter, enabling the analysis of DES surface tension and how it is affected by cosolvent addition. Molecular dynamics (MD) simulations were employed to provide molecular-level insights into the effects of water and short-chain alcohols on the structure and properties of hydrophilic DESs. These simulations revealed competition among hydrogen-bonding interactions, leading to a reor ganization of the DES structure and changes in density, viscosity, and surface tension. In parallel, original experimental data were generated for a series of hydrophilic DESs, providing critical vali dation for the theoretical predictions and filling gaps in the existing literature, particularly regard ing the effect of water. Additionally, the study was extended to hydrophobic DESs based on menthol, thymol, and oc tanoic acid for the extraction of furfuryl alcohol from water. Liquid–liquid equilibrium (LLE) data for these systems were measured for the first time. Both PC-SAFT and coarse-grained MD simu lations (MARTINI 3) successfully predicted the phase behavior, demonstrating the potential of the proposed framework for the design of DES-based separation processes. Integrating these molecular modeling techniques advances the predictive capabilities of thermo dynamic models for DESs, offering valuable insights for the rational design and optimization of sustainable solvent systems. These advancements contribute to the development of DES formu lations tailored for industrial and environmental applications, supporting the transition toward greener chemical processes.
Description
Tesis presentada para optar al grado de Doctor/a en Ciencias de la Ingeniería con mención en Ingeniería Química.
Keywords
Molecular structure, Solvents, Computational chemistry, Thermodynamics