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Klein T, Piszko M, Kankanamge CJ, Kasapis G, Fröba AP. Fick Diffusion Coefficient in Binary Mixtures of [HMIM][NTf 2] and Carbon Dioxide by Dynamic Light Scattering and Molecular Dynamics Simulations. J Phys Chem B 2021; 125:5100-5113. [PMID: 33960781 DOI: 10.1021/acs.jpcb.1c01616] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dynamic light scattering (DLS) experiments and equilibrium molecular dynamics (EMD) simulations were performed in the saturated liquid phase of the binary mixture of 1-hexyl-3-methylimidazolium bis(trifluormethylsulfonyl)imide ([HMIM][NTf2]) and carbon dioxide (CO2) to access the Fick diffusion coefficient (D11). The investigations were performed within or close to saturation conditions at temperatures between (298.15 and 348.15) K and CO2 mole fractions (xCO2) up to 0.81. The DLS experiments were combined with polarization-difference Raman spectroscopy (PDRS) to simultaneously access the composition of the liquid phase. For the first time in an electrolyte-based system, D11 was directly calculated from EMD simulations by accessing the Maxwell-Stefan (MS) diffusion coefficient and the thermodynamic factor. Agreement within combined uncertainties was found between D11 from DLS and EMD simulations for CO2 mole fractions up to 0.5. In general, an increasing D11 with increasing xCO2 could be observed, with a local maximum present at a CO2 mole fraction of about 0.75. The local maximum could be explained by an increasing MS diffusion coefficient with increasing xCO2 over the entire studied composition range and a decreasing thermodynamic factor at xCO2 above 0.7. Finally, PDRS and EMD simulations were combined to investigate the influence of the fluid structure on the diffusive process.
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Affiliation(s)
- Tobias Klein
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 8, 91052 Erlangen, Germany
| | - Maximilian Piszko
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 8, 91052 Erlangen, Germany
| | - Chathura J Kankanamge
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 8, 91052 Erlangen, Germany
| | - Georgios Kasapis
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 8, 91052 Erlangen, Germany.,Institute for Multiscale Thermofluids, School of Engineering, University of Edinburgh, Robert Stevenson Road, Edinburgh EH9 3FB, U.K
| | - Andreas P Fröba
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-University Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 8, 91052 Erlangen, Germany
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Klein T, Wu W, Rausch MH, Giraudet C, Koller TM, Fröba AP. Influence of Liquid Structure on Fickian Diffusion in Binary Mixtures of n-Hexane and Carbon Dioxide Probed by Dynamic Light Scattering, Raman Spectroscopy, and Molecular Dynamics Simulations. J Phys Chem B 2018; 122:7122-7133. [PMID: 29889520 DOI: 10.1021/acs.jpcb.8b03568] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
This study contributes to a fundamental understanding of how the liquid structure in a model system consisting of weakly associative n-hexane ( n-C6H14) and carbon dioxide (CO2) influences the Fickian diffusion process. For this, the benefits of light scattering experiments and molecular dynamics (MD) simulations at macroscopic thermodynamic equilibrium were combined synergistically. Our reference Fickian diffusivities measured by dynamic light scattering (DLS) revealed an unusual trend with increasing CO2 mole fractions up to about 70 mol %, which agrees with our simulation results. The molecular impacts on the Fickian diffusion were analyzed by MD simulations, where kinetic contributions related to the Maxwell-Stefan (MS) diffusivity and structural contributions quantified by the thermodynamic factor were studied separately. Both the MS diffusivity and the thermodynamic factor indicate the deceleration of Fickian diffusion compared to an ideal mixture behavior. Computed radial distribution functions as well as a significant blue-shift of the CH stretching modes of n-C6H14 identified by Raman spectroscopy show that the slowing down of the diffusion is caused by a structural organization in the binary mixtures over a broad concentration range in the form of self-associated n-C6H14 and CO2 domains. These networks start to form close to the infinite dilution limits and seem to have their largest extent at a solute-solvent transition point at about 70 mol % CO2. The current results not only improve the general understanding of mass diffusion in liquids but also serve to develop sound prediction models for Fick diffusivities.
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Affiliation(s)
- Tobias Klein
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT) , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Paul-Gordan-Straße 6 , 91052 Erlangen , Germany
| | - Wenchang Wu
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT) , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Paul-Gordan-Straße 6 , 91052 Erlangen , Germany
| | - Michael H Rausch
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT) , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Paul-Gordan-Straße 6 , 91052 Erlangen , Germany
| | - Cédric Giraudet
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT) , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Paul-Gordan-Straße 6 , 91052 Erlangen , Germany
| | - Thomas M Koller
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT) , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Paul-Gordan-Straße 6 , 91052 Erlangen , Germany
| | - Andreas P Fröba
- Institute of Advanced Optical Technologies - Thermophysical Properties (AOT-TP), Department of Chemical and Biological Engineering (CBI) and Erlangen Graduate School in Advanced Optical Technologies (SAOT) , Friedrich-Alexander-University Erlangen-Nürnberg (FAU) , Paul-Gordan-Straße 6 , 91052 Erlangen , Germany
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Shang J, Yuan T, Zhu H. A new four-dimensional potential energy surface of the Ar–CS2 complex: Dependence on the symmetric and antisymmetric stretching vibrations of CS2. Chem Phys Lett 2016. [DOI: 10.1016/j.cplett.2016.02.016] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Shang J, Yuan T, Zhu H. A new four-dimensional ab initio potential energy surface and predicted infrared spectra for the He–CS2 complex. Theor Chem Acc 2015. [DOI: 10.1007/s00214-015-1755-y] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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