Mutual diffusion coefficients for two n-octane isomers in n-heptane (original) (raw)
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A correlation for predicting diffusion coefficients in alkanes
The Canadian Journal of Chemical Engineering, 1990
A correlation was developed for predicting limiting mutual diffusion coefficients of gaseous and liquid solutes in normal alkane solvents with carbon numbers ranging from 7 to 28 at temperatures to 570 K. The functional form of the correlation is based on the rough hard sphere theory. The parameters needed in the correlation are the molecular weights and hard sphere diameters of the solute and solvent molecules and molar volume of the solvent. The data used in the development of the correlation included 143 measurements with solute/solvent molecular mass ratios ranging from 0.005 to 2.26 and size ratios ranging from 0.3 to 1.3. The average absolute error in predictions was only 6.3%. When the correlation was used to predict literature values for binary n-alkane systems, the average absolute error was 16.7%.
Mutual diffusion coefficients for binary mixtures of normal alkanes
International Journal of Thermophysics, 1982
This paper describes the design and operation of a new instrument for the measurement of diffusion coefficients in liquid mixtures. The instrument employs the principle of Taylor dispersion and has been designed so that it operates as nearly as possible in accordance with the simplest possible mathematical description of the measurement process. The remaining departures from the simple description are accommodated by means of small corrections which have been evaluated from a detailed theory of a practical instrument so that accurate measurement of diffusion coefficients may be performed. The apparatus has been employed to make a series of measurements of the mutual diffusion coefficient of binary mixtures among the normal alkanes hexane, heptane, and octane. The measurements have been performed at atmospheric pressure in the temperature range 290-340 K and over the entire range of mixture composition. It is estimated that the experimental data have an associated uncertainty of _+ 1%. The temperature and composition dependences of the mutual diffusion coefficient have been found to be linear, and the entire body of experimental data is represented by a simple correlating equation within its estimated uncertainty.
Mutual diffusivity in n-heptane + n-hexane isomers
Fluid Phase Equilibria, 1987
A preliminary study of the effect of branching in the binary diffusion of hexane isomer + n-heptane systems is presented. Measurements have been performed with an instrument modeled for the Taylor dispersion technique, at several compositions, at 297 K, for the n-hexane + n-heptane and 2,2-dimethylbutane + n-heptane binary mixtures. The accuracy is estimated to be 1%. The influence of branching is discussed. It was found that the rough hard sphere model for binary diffusion can reproduce the experimental data within 6%. This model was used to predict the binary diffusion coefficients in the 2-methylpentane + n-heptane and 3-methylpentane + n-heptane mixtures, with an estimated accuracy of 5%. I.
Mutual diffusivity in binary mixtures of n-heptane with n-hexane isomers
International Journal of Thermophysics, 1989
This paper presents a study of the influence of branching in the binary diffusion coefficients of n-heptane+n-hexane isomers, in the liquid state. The measurements have been made with the Taylor dispersion technique, at several compositions, at 283 and 298 K, for the X+n-heptane mixtures, where X= n-hexane, 3-methylpentane, 2, 3-dimethylbutane, and 2, 2-dimethylbutane. The results show a very interesting behavior of the composition dependence of the binary diffusion coefficients, presenting a maximum, for compositions about a molar fraction of n-heptane of 0.5, which increases with the increase in the degree of branching, suggesting the possibility of order~tisorder effects caused by stereochemically favored packing in the liquid phase and energetically favored segment interaction in the liquid mixtures. An attempt to apply the van der Waals model to these data could not predict the experimental binary diffusion coefficients of these systems within the experimental accuracy.
Journal of Chemical & Engineering Data, 2000
Taylor dispersion and differential refractometry are used to measure mutual diffusion coefficients (D) for the binary mixtures 1,4-dioxane + water, 1,3-dioxolane + water, and tetrahydrofuran + water at 25°C
Translational-rotational coupling parameters for mutual diffusion inN-octane
AIChE Journal, 1989
The infinite dilution diffusion coefficients of methane, ethane, n-propane, n-pentane, n-heptane, n-decane, n-dodecane, and n-tetradecane have been measured in n-octane using the Taylor dispersion technique in the temperature range 304-435 K at 1.72 x 10' N/m2. Using the framework of the rough hard sphere theory, the values of the translational-rotational coupling parameter have been determined for each solute-solvent pair at each temperature. The coupling parameter was found to be independent of temperature over the entire temperature range of the experiments performed and it has the same value for solutes ranging from n-pentane to n-tetradecane. A calculation scheme is presented for accurate determination of infinite dilution diffusion coefficients for a wide range of solutes in n-octane at a wide temperature range.
Some Measurements of Diffusion in Liquids
The Journal of Physical Chemistry, 1955
Diffusion coefficients for iodine and toluene in a series of saturated hydrocarbons and for benzoic, acet,ic and formic acids in a number of organic solvents are reported. Data were obtained by the diaphragm cell method.
Theory and Experiment of Binary Diffusion Coefficient of n-Alkanes in Dilute Gases
The journal of physical chemistry. A, 2016
Binary diffusion coefficients were measured for n-pentane, n-hexane, and n-octane in helium and of n-pentane in nitrogen over the temperature range of 300 to 600 K, using reversed-flow gas chromatography. A generalized, analytical theory is proposed for the binary diffusion coefficients of long-chain molecules in simple diluent gases, taking advantage of a recently developed gas-kinetic theory of the transport properties of nanoslender bodies in dilute free-molecular flows. The theory addresses the long-standing question about the applicability of the Chapman-Enskog theory in describing the transport properties of nonspherical molecular structures, or equivalently, the use of isotropic potentials of interaction for a roughly cylindrical molecular structure such as large normal alkanes. An approximate potential energy function is proposed for the intermolecular interaction of long-chain n-alkane with typical bath gases. Using this potential and the analytical theory for nanoslender b...
Remarks on the analysis method for determining diffusion coefficient in ternary mixtures
Comptes Rendus Mécanique, 2013
The objective of this work is the determination of diagonal and cross-diagonal molecular diffusion coefficients in a ternary mixture, using the 'Sliding Symmetric Tubes' (SST) technique. The analyzed mixture consists of two aromatics and one normal alkane (tetrahydronaphthalene-dodecane-isobutylbenzene) with an equal mass fraction for all components (1:1:1) at 25 • C. The analytical solution corresponding to the SST technique has been successfully derived. The different fitting procedures were utilized by two scientific teams to subtract diffusion coefficients from the experimentally measured time-dependent concentration field. None of the attempts provided reliable results for the data from a single experiment. The "simplex"-based methods display reasonable results assuming that crossdiagonal coefficients are close to zero, i.e. quasi-binary and diluted mixtures. The results obtained by "trust region method" are satisfactory if the initial guess is good. To achieve better results, it is necessary to increase the number of experimental data.