Binary Diffusion Coefficients for Mixtures of Ionic Liquids [EMIM][N(CN)2], [EMIM][NTf2], and [HMIM][NTf2] with Acetone and Ethanol by Dynamic Light Scattering (DLS)

Rausch, Michael H.; Hopf, Lisa; Heller, Andreas; Leipertz, Alfred; Fröba, Andreas P.

doi:10.1021/jp306116h

Cited by 21 publications

(21 citation statements)

References 33 publications

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“…The associated error bars displayed in the graphs illustrate the expanded uncertainties ( k = 2), which range from 5% to 35% over the whole temperature range and are on average 13%. The latter value is slightly larger than the typical uncertainties obtained in our former studies. − ,, This can be explained by the large number of state points close to Le = 1 where the separation of the hydrodynamic modes related to temperature and concentration remains difficult. Nevertheless, it could be documented that even for the studied small gas mole fractions ranging between 0.7 mol % and 6.0 mol %, uncertainties in the experimental D 11 data of typically smaller than 10% can be obtained when Le ≥ 2.…”

Section: Resultsmentioning

confidence: 57%

Thermal, Mutual, and Self-Diffusivities of Binary Liquid Mixtures Consisting of Gases Dissolved in n-Alkanes at Infinite Dilution

et al. 2018

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In the present study, dynamic light scattering (DLS) experiments and molecular dynamics (MD) simulations were used for the investigation of the molecular diffusion in binary mixtures of liquids with dissolved gases at macroscopic thermodynamic equilibrium. Model systems based on the n-alkane n-hexane or n-decane with dissolved hydrogen, helium, nitrogen, or carbon monoxide were studied at temperatures between 303 and 423 K and at gas mole fractions below 0.06. With DLS, the relaxation behavior of microscopic equilibrium fluctuations in concentration and temperature is analyzed to determine simultaneously mutual and thermal diffusivity in an absolute way. The present measurements document that even for mole gas fractions of 0.007 and Lewis numbers close to 1, reliable mutual diffusivities with an average expanded uncertainty ( k = 2) of 13% can be obtained. By use of suitable molecular models for the mixture components, the self-diffusion coefficient of the gases was determined by MD simulations with an averaged expanded uncertainty ( k = 2) of 7%. The DLS experiments showed that the thermal diffusivity of the studied systems is not affected by the dissolved gas and agrees with the reference data for the pure n-alkanes. In agreement with theory, mutual diffusivities and self-diffusivities were found to be equal mostly within combined uncertainties at conditions approaching infinite dilution of the gas. Our DLS and MD results, representing the first available data for the present systems, reveal distinctly larger mass diffusivities for mixtures containing hydrogen or helium compared to mixtures containing nitrogen or carbon monoxide. On the basis of the broad range of mass diffusivities of the studied gas-liquid systems covering about 2 orders of magnitude from about 10 to 10 m·s, effects of the solvent and solute properties on the temperature-dependent mass diffusivities are discussed. This contributed to the development of a simple semiempirical correlation for the mass diffusivity of the studied gases dissolved in n-alkanes of varying chain length at infinite dilution as a function of temperature. The generalized expression requiring only information on the kinematic viscosity and molar mass of the pure solvent as well as the molar mass and acentric factor of the solute represents the database from this work and further literature with an absolute average deviation of about 11%.

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Section: Resultsmentioning

confidence: 57%

Thermal, Mutual, and Self-Diffusivities of Binary Liquid Mixtures Consisting of Gases Dissolved in n-Alkanes at Infinite Dilution

et al. 2018

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“…Due to large Lewis numbers Le = a / D 11 and a focus on studying the Fickian diffusion in the present study, the temporal resolution was adjusted to minimize the experimental uncertainties in D 11 . Further typical experimental CFs for ILs with dissolved gases close to infinite dilution obtained by DLS can be found in our previous publications. ,, …”

Section: Methodsmentioning

confidence: 69%

Fick Diffusion Coefficient in Binary Mixtures of [HMIM][NTf₂] and Carbon Dioxide by Dynamic Light Scattering and Molecular Dynamics Simulations

et al. 2021

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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 (D 11). The investigations were performed within or close to saturation conditions at temperatures between (298.15 and 348.15) K and CO2 mole fractions (x CO2) 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, D 11 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 D 11 from DLS and EMD simulations for CO2 mole fractions up to 0.5. In general, an increasing D 11 with increasing x CO2 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 x CO2 over the entire studied composition range and a decreasing thermodynamic factor at x CO2 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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“…Depending on the chemical and structural characteristics of the components in a binary liquid mixture, strongly varying trends for the concentration dependency of the Fick diffusivity can be observed. − Systems containing similarly sized and/or weakly associative components typically show an ideal diffusive behavior with a linear concentration dependency . In the case of molecules with larger size differences and highly associative groups such as alcohols, strong deviations from the ideality can be found .…”

Section: Introductionmentioning

confidence: 99%

“…In this context, the analysis of spontaneous short-ranged fluctuations at macroscopic thermodynamic equilibrium by dynamic light scattering (DLS) has proven to be a reliable method for the accurate determination of the Fick diffusivity. It was used in connection with gaseous mixtures, liquid systems at atmospheric pressure, , systems in the near-critical and supercritical region, and liquids containing dissolved gases. ,, …”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

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This study contributes to a fundamental understanding of how the liquid structure in a model system consisting of weakly associative n-hexane ( n-CH) and carbon dioxide (CO) 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 CO 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-CH 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-CH and CO 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 % CO. 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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Binary Diffusion Coefficients for Mixtures of Ionic Liquids [EMIM][N(CN)₂], [EMIM][NTf₂], and [HMIM][NTf₂] with Acetone and Ethanol by Dynamic Light Scattering (DLS)

Cited by 21 publications

References 33 publications

Thermal, Mutual, and Self-Diffusivities of Binary Liquid Mixtures Consisting of Gases Dissolved in n-Alkanes at Infinite Dilution

Thermal, Mutual, and Self-Diffusivities of Binary Liquid Mixtures Consisting of Gases Dissolved in n-Alkanes at Infinite Dilution

Fick Diffusion Coefficient in Binary Mixtures of [HMIM][NTf₂] and Carbon Dioxide by Dynamic Light Scattering and Molecular Dynamics Simulations

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

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Binary Diffusion Coefficients for Mixtures of Ionic Liquids [EMIM][N(CN)2], [EMIM][NTf2], and [HMIM][NTf2] with Acetone and Ethanol by Dynamic Light Scattering (DLS)

Cited by 21 publications

References 33 publications

Thermal, Mutual, and Self-Diffusivities of Binary Liquid Mixtures Consisting of Gases Dissolved in n-Alkanes at Infinite Dilution

Thermal, Mutual, and Self-Diffusivities of Binary Liquid Mixtures Consisting of Gases Dissolved in n-Alkanes at Infinite Dilution

Fick Diffusion Coefficient in Binary Mixtures of [HMIM][NTf2] and Carbon Dioxide by Dynamic Light Scattering and Molecular Dynamics Simulations

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

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Binary Diffusion Coefficients for Mixtures of Ionic Liquids [EMIM][N(CN)₂], [EMIM][NTf₂], and [HMIM][NTf₂] with Acetone and Ethanol by Dynamic Light Scattering (DLS)

Fick Diffusion Coefficient in Binary Mixtures of [HMIM][NTf₂] and Carbon Dioxide by Dynamic Light Scattering and Molecular Dynamics Simulations