Thermal diffusion in mixtures with association reactions. Thermal diffusion factors for methanol-benzene mixtures

Johnson, Jung-chen Chou; Beyerlein, Adolph L.

doi:10.1021/j100501a021

Cited by 17 publications

(6 citation statements)

References 9 publications

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“…Associated mixtures often show a sign change of the Soret coefficient with concentration [28][29][30] so that the direction of the thermal diffusion process is predominantly guided by excess properties and not by the properties of the mixing partners like the difference in mass or moment of inertia. Such behavior is expected from the non-ideality of such mixtures due to the hydrogen bond formation.…”

Section: Introductionmentioning

confidence: 99%

Systematic study of the thermal diffusion in associated mixtures

Polyakov

Wiegand

2008

The Journal of Chemical Physics

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We performed systematic temperature and concentration dependent measurements of the Soret coefficient in different associated binary mixtures of water, deuterated water, dimethyl sulfoxide (DMSO), methanol, ethanol, acetone, methanol, 1-propanol, 2-propanol, propionaldehyde using the so called thermal diffusion forced Rayleigh scattering method. For some of the associating binary mixtures such as ethanol/water, acetone/water and DMSO/water the concentration x ± w at which the Soret coefficient changes its sign does not depend on temperature and is equal to the concentration x × w where the Soret coefficient isotherms intersect. While for others such as 1-propanol/water, 2-propanol/water and ethanol/DMSO the sign change concentration is temperature dependent, which is the typical behavior observed for non-associating mixtures. For systems with x ± w = x × w we found that x ± w depends linearly on the ratio of the vaporization enthalpies of the pure components. Probably due to the similarity of methanol and DMSO we do not observe a sign change for this mixture. The obtained results are related to structural changes in the fluid observed by nuclear magnetic resonance, mass specrometric and X-ray experiments in the literature. Furthermore we discuss the influence of hydrophilic and hydrophobic interactions and the solubility on thermal diffusion behavior.

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Section: Introductionmentioning

confidence: 99%

Systematic study of the thermal diffusion in associated mixtures

Polyakov

Wiegand

2008

The Journal of Chemical Physics

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“…Although this theory was developed for isotopic mixtures, it predicts the same steady state separations as theories [1][2][3][4] successfully used for other types of liquid mixtures [6][7][8][9] within the approximations where the "forgotten effect" (about 3% [4,7]) and small temperature difference effects (less then 0.1 % for temperature differences less than 57 °C, [4]) are neglected. The transient predictions are also expected to be applicable to nonisotopic mixtures as well as isotopic mixtures within the framework of these same approximations.…”

Section: Theory For the Approach To Steady Statementioning

confidence: 99%

“…Home and Bearman [1][2][3][4][5] have developed a precise steady state theory of liquid thermogravitational diffusion and considerable success has been achieved in utilizing this technique as a means of measuring thermal diffusion factors of binary mixtures [6][7][8][9]. This method has two distinct advantages over the pure thermal diffusion [10] and flow cell methods [11] namely; (i) very precise temperature control is not required and (ii) the sensitivity of the method can be increased by decreasing the width of the cylindrical annulus containing the liquid mixture.…”

Section: Introductionmentioning

confidence: 99%

Experimental Studies on the Approach to Steady State in Thermogravitational Diffusion

Ma¹,

Stanford²,

Beyerlein³

1983

Journal of Non-Equilibrium Thermodynamics

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The rate of approach to steady state in thermogravitational diffusion is investigated for two cylindrical thermogravitational diffusion apparatuses with annular gap widths of 0.65 mm and 1.0 mm, respectively. The mixtures studied are; carbon tetrachloride-cyclohexane, benzene-methanol, and carbon tetrachlorideethanol at a mean temperature of 25 °C. The results confirm earlier conclusions (D.J.Stanford, A.Beyerlein, J. Chem. Phys., 58 (1973), 4338) that the steady state theory of thermogravitational diffusion predicts experimental separations well within experimental error. The investigations also show that the relaxation times, describing the approach to steady state, have a dependence on temperature difference and thermodynamic properties that is accurately predicted by theory. However, the relaxation times appear to vary in proportion to the inverse of the annular gap width to 5.3 ± 0.2 power, rather than to the sixth power as theory predicts. Thus one must calibrate the apparatus for the effect of apparatus dimensions if one wishes to use transient thermogravitational separations to estimate diffusion coefficients. A rather surprising result of this investigation is that as a first approximation the relaxation times are proportional to the isothermal diffusion coefficient but are independent of the thermal diffusion factor. After calibration of the apparatuses the accuracy of the diffusion coefficients estimated from the transient thermogravitational diffusion separations is about 10%.

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“…Molecular association also has important consequences for the transport properties of solutions, such as viscous flow, − diffusion, − and thermal diffusion. − In a study of the role of hydrogen bonding in diffusion processes, Longsworth 19 measured binary mutual diffusion coefficients for alcohols and carboxylic acids in carbon tetrachloride solutions. For comparison, diffusion coefficients for nonassociating solutes were also measured.…”

Section: Introductionmentioning

confidence: 99%

Coupled Diffusion of Mixed Methanol + Ethanol Clusters in Carbon Tetrachloride Solutions

and

Líu

2001

J. Phys. Chem. B

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Ternary mutual diffusion coefficients are measured for methanol + ethanol + carbon tetrachloride solutions at 25 °C and 0.200 mol dm -3 of total alcohol. The alcohol components in these solutions diffuse as free MeOH and EtOH molecules in local equilibrium with hydrogen-bonded alcohol clusters. Although each alcohol cotransports the other alcohol in the form of mixed (MeOH) n (EtOH) m clusters, negative cross-diffusion coefficients for this system indicate that each mole of diffusing alcohol drives counterflows of up to 0.5 mol of the other alcohol. The results are interpreted by relating the measured total alcohol fluxes to the fluxes of the alcohol monomers and associated species. Added ethanol increases the concentrations of the mixed clusters but reduces the concentrations of the MeOH monomers. The resulting flux of MeOH monomers up the ethanol gradient exceeds the flux of the larger, less-mobile associated methanol species down the ethanol gradient, producing a net counterflow of methanol. Similarly, methanol gradients produce counterflows of ethanol. Binary diffusion in methanol + carbon tetrachloride and ethanol + carbon tetrachloride solutions is also discussed.

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Thermal diffusion in mixtures with association reactions. Thermal diffusion factors for methanol-benzene mixtures

Cited by 17 publications

References 9 publications

Systematic study of the thermal diffusion in associated mixtures

Systematic study of the thermal diffusion in associated mixtures

Experimental Studies on the Approach to Steady State in Thermogravitational Diffusion

Coupled Diffusion of Mixed Methanol + Ethanol Clusters in Carbon Tetrachloride Solutions

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