Prediction of transport diffusion coefficients of multicomponent mixtures in the liquid state
Final Report Abstract
Multicomponent diffusion phenomena pose significant challenges due to their intricate nature and the limited availability of experimental data. This project sought to bridge this gap by developing and employing molecular simulation tools to gain microscopic insights into diffusion mechanisms and predict diffusion coefficients of binary, ternary, and quaternary mixtures. Central to this project was the refinement and development of molecular force field models for various substances, ensuring accurate representation of transport properties. The simulation tool, ms2, was augmented with new functionalities to facilitate the sampling of diffusion coefficients, the thermodynamic factor and hydrogen bonding statistics, enabling a comprehensive analysis of diffusion behavior in multicomponent mixtures. Employing equilibrium molecular dynamics simulations as well as the Green-Kubo and Einstein equations, Maxwell-Stefan, Fick and intradiffusion coefficients were determined for mixtures in the homogeneous fluid phase, near phase separation and in the near-critical region. Further, this project introduced a new approach for correcting finite size-effects of Maxwell-Stefan diffusion coefficients of multicomponent mixtures, also addressing inherent limitations of other existing correction techniques. Thanks to the collaboration with Prof. Valentina Shevtsova, experiments were performed to complement molecular simulation analyse of diffusional behavior. As an example, the influence of alcohol size on the elements of the Fick diffusion coefficient matrix for ternary systems including benzene, acetone and methanol, ethanol or isopropanol was analysed. Notably, it was found that the diffusion behavior of the main element of the Fick diffusion coefficient matrix related to benzene is largely independent of alcohol chain length, with microscopic arrangements and intermolecular interactions playing pivotal roles in this observation. The work was extended to quaternary mixtures, specifically the mixture water + methanol + ethanol + isopropanol was studied together with its ternary and binary subsystems. The lack of experimental data on the quaternary mixture motivated the assessment of the consistency and plausibility of the simulation results by examining the asymptotic behavior of the elements of the Fick diffusion coefficient matrix. Further, the influence of the reference frame and the component order on the numerical values of this diffusion matrix was exhaustively examined. For this purpose, density measurements of the studied quaternary mixture and its subsystems were done to obtain the required partial molar volumes. The cross elements of the Fick diffusion coefficient matrix were found to be highly sensitive to the reference frame and component order. Thus, it was highlighted that the assessment of the presence of significant diffusional cross effects cannot be done only based on one set of Fick diffusion coefficients. Diffusion near phase separation was analysed for the binary mixture cyclohexane + methanol and the ternary mixture cyclohexane + toluene + methanol. As the miscibility gap is approached, the intradiffusion coefficients remain stable, whereas the values of the Maxwell-Stefan diffusion increase as well as the significance of cross diffusion effects. The diffusion behavior of CO2 mixtures in the near-critical region at the Widom line, i.e., the dynamical crossover between the gas- and liquid like supercritical regions, was systematically investigated in this project. The presence of diverse anomalies and unexpected behavior of thermodynamic and transport properties was analyzed and explained at the microscopic level by the presence of clustering, density fluctuations and large correlation lengths that are a reminiscence of the critical point. Moreover, a two-step approach was developed to predict Fick diffusion coefficient of hydrocarbons diluted in supercritical CO2 based on entropy scaling and solute mass dependencies. In essence, this project not only advanced our understanding of diffusion behavior in multicomponent systems, but also offers practical insights into predicting and interpreting diffusion coefficients across various scenarios, laying the foundation for further explorations of this domain.
Publications
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Diffusion of methane in supercritical carbon dioxide across the Widom line. Scientific Reports, 9(1).
Guevara-Carrion, Gabriela; Ancherbak, Sergiy; Mialdun, Aliaksandr; Vrabec, Jadran & Shevtsova, Valentina
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Do ternary liquid mixtures exhibit negative main Fick diffusion coefficients?. Physical Chemistry Chemical Physics, 21(4), 2140-2152.
Kozlova, S.; Mialdun, A.; Ryzhkov, I.; Janzen, T.; Vrabec, J. & Shevtsova, V.
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Fick Diffusion Coefficient Matrix of a Quaternary Liquid Mixture by Molecular Dynamics. The Journal of Physical Chemistry B, 124(22), 4527-4535.
Guevara-Carrion, Gabriela; Fingerhut, Robin & Vrabec, Jadran
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Density and Partial Molar Volumes of the Liquid Mixture Water + Methanol + Ethanol + 2-Propanol at 298.15 K and 0.1 MPa. Journal of Chemical & Engineering Data, 66(6), 2425-2435.
Guevara-Carrion, Gabriela; Fingerhut, Robin & Vrabec, Jadran
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Diffusion in multicomponent aqueous alcoholic mixtures. Scientific Reports, 11(1).
Guevara-Carrion, Gabriela; Fingerhut, Robin & Vrabec, Jadran
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Diffusion of the carbon dioxide–ethanol mixture in the extended critical region. Physical Chemistry Chemical Physics, 23(4), 3106-3115.
Chatwell, René Spencer; Guevara-Carrion, Gabriela; Gaponenko, Yuri; Shevtsova, Valentina & Vrabec, Jadran
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Predicting and Rationalizing the Soret Coefficient of Binary Lennard‐Jones Mixtures in the Liquid State. Advanced Theory and Simulations, 5(11).
Zimmermann, Nils E. R.; Guevara‐Carrion, Gabriela; Vrabec, Jadran & Hansen, Niels
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Thermodynamics of supercritical carbon dioxide mixtures across the Widom line. Physical Chemistry Chemical Physics, 24(46), 28257-28270.
Saric, Denis; Guevara-Carrion, Gabriela & Vrabec, Jadran
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Diffusion of hydrocarbons diluted in supercritical carbon dioxide. Scientific Reports, 13(1).
Saric, Denis; Guevara-Carrion, Gabriela; Gaponenko, Yury; Shevtsova, Valentina & Vrabec, Jadran
