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We report measurements of the diffusion coefficients of CO2 and N2 in pure water at temperatures between (298.15 and 423.15) K and pressures between (15 and 45) MPa. The measurements were made by the Taylor dispersion method and have a standard relative uncertainty of 2.3 %. The results were found to be essentially independent of pressure over the range investigated and a simple relation, based on the Stokes–Einstein equation, is proposed to correlate the experimental data. Some experimental difficulties arising in the measurement of the diffusivities of slightly soluble acid-gas solutes such as CO2 in water are also discussed.

Binary diffusion coefficients (D12) and retention factors (k) of platinum(II) acetylacetonate at infinitesimal concentration in supercritical (sc) carbon dioxide (CO2) were measured by the chromatographic impulse response method with a poly(ethylene glycol) coated capillary column at temperatures from (308.15 to 343.15) K and pressures from (8.5 to 40.0) MPa, and D12 in liquid ethanol at temperatures from (298.15 to 333.15) K and atmospheric pressure by the Taylor dispersion method. As has been seen for our previously reported data on other metal complexes measured in sc CO2 and organic solvents, the D12 data in sc CO2 and liquid ethanol were represented by a function of temperature and solvent viscosity. The D12 values for metal complexes were not related to the solute molecular weights. The k values in sc CO2 were expressed by a function of temperature and CO2 density.

Mutual diffusion coefficients for aqueous solutions of 3-aminopropanoic acid (β-alanine), 4-aminobutanoic acid (γ-aminobutyric acid), 5-aminopentanoic acid, 6-aminohexanoic acid, and 7-aminoheptanoic acid at infinitesimal concentration were measured at atmospheric pressure and temperatures from (298.2 to 333.2) K using the Taylor dispersion method. The results were compared with those of the structural isomers measured in our previous studies to examine the effect of position of amino and carboxylic acid groups on the values of diffusion coefficients. The diffusion coefficients of all amino acid isomers were almost the same, indicating that the diffusion coefficients of amino acids measured in our studies were mostly determined by the molar mass and the increase in the distance between amino and carboxylic acid groups was not an important factor. The temperature dependences of the diffusion coefficients were well-correlated with viscosity of water, η, as D12/T = αηβ where D12 is the diffusion coefficient ...

Ternary mutual diffusion coefficients (D11, D22, D12, and D21) measured by the Taylor dispersion method at T = 298.15 K in two different laboratories (University of Naples, Federico II, Italy, and University of Coimbra, Portugal) are reported for aqueous systems, involving as components 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) or β-cyclodextrin (β-CD) and theophylline. The aim of the paper was to determine the transport properties of these systems as well as the presence of an inclusion mechanism. On the basis of the diffusion coefficient data it can be argued that theophylline is included neither into β-cyclodextrin nor into 2-hydroxypropyl β-cyclodextrin. The variations of the main diffusion coefficients with composition are ascribable to nonspecific solute–solute interactions such as the viscosity increase induced by the presence of the drug or to an obstruction effect of which the bulky cyclodextrin is responsible.

The influence of sodium chloride and hydrochloric acid on the diffusion of aqueous nickel chloride has been investigated by using Taylor dispersion to measure ternary mutual diffusion coefficients for aqueous solutions of NiCl2 + NaCl and NiCl2 + HCl at 298.15 K and carrier concentrations from (0.000 to 0.050) mol·dm–3 for each solute. Mutual diffusion coefficients estimated from limiting ionic conductivities using Nernst equations are used to discuss the composition dependence of the diffusion coefficients and the electrostatic mechanism for the strongly coupled diffusion of the solutes.

Diffusion coefficients of potassium chloride in potassium chloride solutions of molality (0, 1, 2.5, and 4.5) mol·kg–1 were measured at temperatures of (298.15, 323.15, 348.15, 373.15, and 423.15) ...

In this study, infinite dilution diffusion coefficients of aromatic compounds in ternary mixtures were measured at 298.15 K using the Taylor dispersion technique. The experimental data of benzene i...

Binary diffusion coefficients D12 and retention factors k of ferrocene and 1,1′-dimethylferrocene at infinite dilution in supercritical (sc) carbon dioxide were measured by the chromatographic impulse response (CIR) method at temperatures from (308.2 to 323.2) K over a pressure range from (8.0 to 40.3) MPa for ferrocene and from (8.2 to 40.1) MPa for 1,1′-dimethylferrocene. The D12 data for ferrocene were also measured by the Taylor dispersion method with two injection procedures of ferrocene: ferrocene dissolved both in sc CO2 and in liquid hexane. The D12 values of ferrocene were not affected by the injection methods and agreed with those measured by the CIR method. As has been seen for various organic compounds measured in our previous reports, the D12 data for both metal complexes were correlated with the hydrodynamic equation D12/T = αηβ, where η is the CO2 viscosity and α and β are the constants determined by each solute. The retention factors were also correlated with CO2 density.

The Taylor dispersion method was used to measure limiting interdiffusion coefficients for benzyl alcohol, 2-phenylethanol, 3-phenylpropan-1-ol, 4-phenylbutan-1-ol, and 5-phenylpentan-1-ol in water ...

Taylor dispersion has gained popularity for the measurement of mutual diffusion coefficients (Dik) for multicomponent solutions. In practice, however, the analysis of dispersion profiles, like the analysis of free-diffusion boundaries measured by optical interferometry, becomes ill-conditioned for solutes of similar diffusivities if the eigenvalues of the Dik matrix differ by less than about (5 to 10) %. These numerical difficulties, well-known in studies of multiexponential decays with nearly identical decay constants, can produce large errors in measured Dik coefficients and even rule out studies of important systems, including solutions of isomers, oligomers, polydisperse polymers, strongly associated solutes, and mixed electrolytes composed of ions of similar mobility. To investigate diffusion in these systems, equations are derived for the Taylor dispersion profiles produced by ternary mutual diffusion with equal eigenvalues. Using these equations, a simple least-squares procedure is developed to eva...

Ternary mutual diffusion coefficients measured by the Taylor dispersion method are reported for aqueous solutions of CaCl2−caffeine at carrier concentrations from (0.0025 to 0.0500) mol·dm−3 for each solute, respectively. The results are compared with those obtained for the binary systems H2O−CaCl2 and H2O−caffeine, also reported here. From these data, it is possible to make conclusions about the influence of the caffeine solutes in the diffusion of calcium chloride and to contribute to a better understanding of the structure of this system.

The binary mass diffusion coefficients of cellulose acetate butyrate in methyl ethyl ketone solutions (CAB + MEK) have been measured under atmospheric pressure at temperatures from (293 to 323) K and mass fractions from 0.05 to 0.6. The present experimental apparatus is based on the Soret forced Rayleigh scattering method (S-FRSM), which utilizes the Soret effect to create periodic spatial concentration modulation of micrometer-order fringe spacing in a sample binary liquid mixture due to the absorption of an optical interference grating generated by two intersecting heating laser beams. The decay of the concentration modulation by the mass diffusion process is monitored by the diffraction of a probing laser beam. This method provides several advantages in comparison with conventional techniques such as Taylor dispersion or diaphragm cells; namely, a single measurement can be performed within a short time [(10−3 to 10−2) s], with small temperature and concentration changes (ΔT < 10−2 K and Δc < 10−5) usin...

The concentration dependence of the mutual diffusion coefficients in the ternary liquid mixture cyclohexane + toluene + methanol is determined at 298.15 K by Taylor dispersion technique along two concentration paths of a constant toluene mole fraction of x2 = 0.40 and x2 = 0.60, respectively. The four elements of the matrix of mutual diffusion coefficients, the eigenvalues, and the determinant of the matrix are given.

The concentration dependence of the mutual diffusion coefficients in the ternary liquid mixture cyclohexane (1) + toluene (2) + methanol (3) is determined at 298.15 K by the Taylor dispersion technique along three concentration paths of a constant toluene mole fraction of x2 = 0.05, x2 = 0.10, and x2 = 0.20, ranging from the binary subsystems toward the liquid−liquid phase boundary of the ternary system. The four elements of the matrix of mutual diffusion coefficients, the corresponding eigenvalues, and the determinant of the matrix are given.

Diffusion coefficients for the binary system n-decyl dimethyl phosphine oxide + water have been studied at 25 °C, with the aim to quantitatively describe the surfactant micellization process in aqueous medium. Accurate mutual diffusion coefficients have been measured by the Taylor dispersion technique. Intradiffusion coefficients of both components have been measured by the pulsed gradient spin echo (PGSE)-FT NMR technique. The data have been compared and interpreted in the framework of the equilibrium model of surfactant self-aggregation. Interpolation of the mutual diffusion coefficients has allowed us to estimate reliable values of the average number of surfactant molecules involved in the formation of a micellar aggregate and the constant of the equilibrium between these aggregates and surfactant unimers. Interpolation of water intradiffusion coefficients has allowed us to estimate the number of water molecules involved in the hydration of surfactants in unimeric and micellized form.

Diffusion coefficients of the potassium salt of taurine, sarcosine, L-proline, and glycine have been determined in aqueous solutions using the Taylor dispersion technique over a temperature range from (293 to 368) K and salt concentrations ranging from (0 to 3.0) mol·dm-3. The diffusion coefficients of absorbed N2O in aqueous solutions of the potassium salt of taurine, sarcosine, L-proline, and glycine have been determined over a temperature range from (293 to 333) K and salt concentrations ranging from (1.0 to 3.0) mol·dm-3. The experimental results have been compared to estimated values from a modified Stokes-Einstein relation and available literature data. The diffusivities can be estimated with sufficient accuracy using a modified Stokes-Einstein relation. The diffusion coefficients of CO2 in the aqueous amino acid salt solutions can be estimated by means of the N2O analogy.

Infinite dilution diffusion coefficients of benzothiophene, dibenzothiophene, acridine, naphthalene, and anthracene in tetradecane have been measured in a temperature range from (313.2 to 473.2) K using the Taylor dispersion technique. Predicted values based on the correlations of Wilke−Chang and Tyn−Calus deviate up to 35 %. An Arrhenius type of equation was used to describe the temperature dependence of the diffusion coefficients with an accuracy on average of less than 5 %.

Diffusion coefficients of aromatic compounds at infinite dilution in binary mixtures have been measured at 298.15 K with respect to composition using the Taylor dispersion technique. The binary mixtures considered in this work were from alcohols (methanol, ethanol) and acetone with hexane, heptane, cyclohexane, carbon tetrachloride, and chloroform; the aromatic compounds were benzene, benzaldehyde, acetophenone, and phenol. The purpose of this work was to study the influence of the polarity of the binary mixtures on diffusion coefficients. The data were correlated by the Leffler−Cullinan equation, using the measured values of diffusion coefficients in pure solvents and estimating the viscosity of the binary mixtures with group contribution methods. Special attention was paid to the capability of models to take into account the polarity of the mixtures; for this purpose, in addition to the Grunberg−Nissan model, the UNIFAC-VISCO group contribution method was also considered.

Mutual diffusion coefficients for 2-(diethylamino)ethanol (2) in water (1) were experimentally obtained by the Taylor dispersion technique from x2 = 0 to ≈ 0.2, at T = 298 K and T = 303 K. Viscosities and surface tensions were measured in the entire composition range using capillary viscometry and ring tensiometry, respectively. Viscosities were measured at the above temperatures, and surface tensions were measured at intervals of 5 K in the temperature range from (283 to 303) K. Information about intermolecular interactions, hydration modes, and solute aggregation is provided through the combined study of the observed changes in diffusion coefficients, viscosities, and surface tension with composition. Conclusions obtained are compared with those taken from volumetric and optical properties for the same system.

Taylor dispersion has gained widespread popularity for measuring diffusion in liquids. The usual procedure is to inject small volumes of solution containing solute at concentration c + Δc into carrier streams of composition c. Binary mutual diffusion coefficients D are evaluated from the Gaussian distribution of the dispersed solute measured at the outlet of a long capillary tube. As a result of strong dilution of the injected solute with the carrier solution, obtaining favorable signal-to-noise ratios for the measured profiles can require unacceptably large Δc values for solutions with strongly composition-dependent diffusion coefficients or broad dispersion profiles produced by slowly diffusing solutes. For these systems, D can be reliably evaluated from error-function profiles generated by changing the solution flowing into dispersion tube from composition c − (Δc/2) to c + (Δc/2). There are no dilution factors, so Δc can be orders of magnitude smaller than the values employed in conventional pulse...

Binary mutual diffusion coefficients measured by the Taylor dispersion method are reported for aqueous solutions of α-cyclodextrin (α-CD), 2-hydroxypropyl-α-cyclodextrin (HP-α-CD), and 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) at concentrations from (0.002 to 0.010) mol·dm-3 at temperatures from (298.15 to 312.15) K. The hydrodynamic radius and activation energy for the diffusion of aqueous α-CD, HP-α-CD, and HP-β-CD are calculated from the experimental results. In addition, the Hartley equation and the measured diffusion coefficients are used to estimate activity coefficients for aqueous α-CD, HP-α-CD, and HP-β-CD.

The concentration dependence of the mutual diffusion coefficients in the ternary liquid mixture glycerol + acetone + water is determined at 298.15 K by the Taylor dispersion technique. As a continuation of previous measurements, we selected three concentration paths of a constant water mole fraction of x3 = 0.1, 0.2, and 0.3, respectively, ranging from the limit of the binary subsystem toward the phase boundary in the ternary system. The eigenvalues and the determinant of Fick's diffusion coefficient matrix are given.

Infinite dilution binary diffusion coefficients D12 for arabinose, xylose, glucose, mannose, galactose, and sucrose in water were measured over the temperature range from (273.2 to 353.2) K at 0.1 MPa with the Taylor dispersion method. The values of D12/T were well correlated with water viscosity for each solute with average absolute deviation AAD < 1.7 %. The accuracies for various predictive correlations were also examined.

Infinite dilution binary diffusion coefficients (D12) were determined for 10 α-amino acids, glycine, alanine, α-amino-n-butyric acid, norvaline, valine, norleucine, leucine, isoleucine, alloisoleucine, and tert-leucine in water over a temperature range from (293.2 to 333.2) K with the Taylor dispersion technique. At 298.2 K, the literature data for the two α-amino acids alloisoleucine and tert-leucine are not available, whereas the determined D12 values of the others are in good agreement with the data reported previously within the experimental errors of ± 2.0 %. The D12 values for all α-amino acids studied were well-represented by two simple correlations, and the accuracies for the correlations were examined for each α-amino acid.

Accurate diffusion coefficient data are reported for highly nonideal binary mixtures. The mixtures consist of an alcohol (ethanol, 1-propanol, 1-butanol) dissolved in hexane, cyclohexane, carbon tetrachloride, or toluene. All measurements have been conducted over the whole concentration range at various temperatures, (25, 30, and 35) °C, by means of the Taylor dispersion technique. The uncertainty of the reported data is estimated to be within 3.10 -11 m 2 .s -1 .

The concentration dependence of the mutual diffusion coefficients in the ternary liquid mixture glycerol + acetone + water is determined at 298.15 K by the Taylor dispersion technique along two concentration paths of constant water mole fractions of 0.468 and 0.420, ranging from the binary subsystem toward the phase boundary in the vicinity of the critical solution point. The eigenvalues of Fick's diffusion coefficient matrix are given, and the influence of the optical properties of the system on the diffusion coefficient determination is discussed. It was found that the determinant |D| continuously declines on approaching the phase boundary.

The diffusion coefficients of alkanolamines in water at infinite dilution and the mutual diffusion coefficients of aqueous diglycolamine, triethanolamine, 2-amino-2-methyl-l-propanol, and 2-piperidineethanol solutions have been studied by using the Taylor dispersion method. Experimental results for temperatures from (30 to 70) °C and at atmospheric pressure as functions of the concentration of alkanolamines from {0.5 to 3 (or 4)} kmol·m-3 are reported. The uncertainty of the measurement is estimated to be ±2.0%. The diffusion coefficients of alkanolamines in water at infinite dilution were found to vary systematically with the molar mass of the alkanolamines. The obtained mutual diffusion coefficients were correlated by using both a simple relation and the UNIDIF equation. The measured mutual diffusivity data are also well represented by a free-volume expression. The results of this study can be used to develop the kinetic model for gas absorption using aqueous alkanolamine solutions as absorbents.

Diffusion coefficients for the binary system glycerol + water have been studied at 25 °C. Accurate mutual diffusion coefficients have been measured by the Taylor dispersion and Gouy interferometric techniques. Intradiffusion coefficients of both components have been measured by the pulsed gradient spin-echo- Fourier transform NMR technique. The collected diffusion coefficients have been combined with data of water excess chemical potential present in the literature to calculate the velocity correlation coefficients. The results have been interpreted in terms of molecular interactions.

A Taylor dispersion method was used to measure quaternary diffusion coefficients (D11, D22, D33, D12, D13, D21, D23, D31 and D32) of the four-component system β-cyclodextrin + KCl + caffeine + water at 298.15 K at carrier concentrations from (0.002 to 0.010) mol·dm−3 for each solute with an inaccuracy of ± (1 to 2) %. These diffusion coefficients were measured in order to obtain a better understanding of the structure of these systems, e.g., for reliable and safe delivery of precise dosages of medical drugs.

Diffusion coefficients of the 12 aromatic compounds phenol, aniline, pyridine, 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 2-chlorophenol, 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, o-cresol, m-cresol, p-cresol, and 3,5-dihydroxytoluol (orcinol) have been measured in aqueous solution at (277.15, 298.15, and 323.15) K using the Taylor dispersion technique. In addition, aqueous solutions of caffeine, benzene, tetraethylammonium perchlorate, and tetramethylammonium perchlorate have been studied where reliable diffusion data are available in the literature in order to test the apparatus. The method provides data with an accuracy to within ±1.5%. In the range of concentrations studied (0.2 × 10-4 to 5.8 × 10-4 mol L-1) the diffusion coefficient depends on the concentration and values at infinite dilution can be obtained by extrapolation. A modified Wilke−Chang equation was found to correlate the data with respect to their dependence on temperature and molecular size of the aromatic compounds.

A Taylor dispersion method has been used to measure ternary diffusion coefficients of three-component aqueous systems, D11, D22, D12, and D21, for aqueous solutions of CuCl2−theophiline at temperatures of (298 and 310) K at carrier concentrations from (0.000 to 0.010) mol·dm−3, for each solute, respectively. The results are compared with these obtained for (H2O + CuCl2) and (H2O + 1,3-dimethyl-7H-purine-2,6-dione), also reported here.

The mutual diffusion coefficients of binary liquid mixtures of diethyl oxalate with ethanol and butan-1-ol in the complete mole fraction range were measured by the Taylor dispersion method. Experimental results at 293.15, 303.15, and 313.15 K are reported. The data are fitted by polynomial equations with an average absolute deviation of 1%. These experimental data are also satisfactorily correlated by a recently developed local composition UNIDIF model.

A Taylor dispersion method is used to measure ternary multicomponent diffusion coefficients of three-component liquid systems. Ternary mutual diffusion coefficients measured by this method (D11, D22, D12, and D21) are reported for aqueous solutions of β-cyclodextrin (β-CD) + caffeine at 298.15 K at carrier concentrations from (0.000 to 0.010) mol·dm−3, for each solute, respectively. These diffusion coefficients have been measured having in mind a better understanding of the structure of these systems and the thermodynamic behavior of caffeine and cyclodextrin in solution.

Infinite dilution binary diffusion coefficients of C5-monoalcohols in water were measured by the Taylor dispersion method at 273.2 K to 353.2 K and 0.1 MPa. At each temperature it was found that the D12 values for the isomers increase with the boiling point of the pure alcohols. The D12 values were correlated with temperature, water viscosity, and solute boiling point. The accuracy in the correlation was superior to the various correlations reported in the literature.

Interdiffusion coefficients Dao in octan-1-ol of benzene, toluene, chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, bromobenzene, 1,2-dibromobenzene, and 1,4-dibromobenzene have been measured at 25 °C at average solute mole fractions from 0.001 to 0.000 05 using the Taylor dispersion technique. The Dao values range from 0.5 × 10-9 m2/s to 0.3 × 10-9 m2/s with standard deviations below 4% in all but the highest dilutions and show only minor (and statistically insignificant) variations with solute concentration. In addition, corresponding interdiffusion coefficients of methanol, ethanol, propan-1-ol, butan-1-ol, 2-methylpropan-2-ol and phenol were determined at average mole fractions around 0.0004. For both groups of compounds, distinct but separate dependencies of Dao on molecular size were observed. The results are discussed from the viewpoint of the Stokes−Einstein equation, and in comparison with literature data for the corresponding diffusion in water. The analysis reveals different dependencie...

Absorption rates of gaseous CO2 into aqueous diethanolamine (DEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO2 in solution but very sensitive to the diffusion rate of bicarbonate, protonated DEA, and carbamate ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. The diffusion coefficient of DEA in water was also measured using a Taylor dispersion apparatus. A numerical model was developed and used to regress diffusion coefficients of bicarbonate, carbamate, and protonated amine from measured absorption rates. CO2 absorption rates and diffusion coefficients of bicarbonate, carbamate, and protonated DEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % DEA in water.

Absorption rates of gaseous CO2 into aqueous N-methyldiethanolamine (MDEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO2 in solution but very sensitive to the diffusion rate of bicarbonate and protonated MDEA ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. A numerical model was developed on the basis of these observations. The model was used to regress diffusion coefficients of bicarbonate and protonated amine, which must be equivalent by electroneutrality arguments, from measured absorption rates. Complete modeling of the absorption process also required data for the diffusion coefficient of MDEA in water. These were measured using a Taylor dispersion apparatus. CO2 absorption rates and diffusion coefficients of bicarbonate and protonated MDEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, ...

The interdiffusion coefficient Daw of six hydrophobic benzene derivatives (a = chlorobenzene, 1,2-dichlorobenzene, 1,4-dichlorobenzene, bromobenzene, 1,2-dibromobenzene, 1,4-dibromobenzene) in aqueous solution (w) at 25 °C is measured at different concentrations below 10-5 solute mole fractions using the Taylor dispersion technique. On the basis of the experimental uncertainty around 4%, a distinct concentration dependence is not recognizable. Analysis of the interdiffusion coefficients with the Stokes−Einstein equation shows greater values than expected from the limit of a complete solute−solvent contact (“stick limit”), and in addition substance-specific deviations. Chemical engineering correlations for presently available from the literature yield unsatisfactory results for this class of predominantly hydrophobic compounds.

Taylor dispersion is used to measure mutual diffusion coefficients (D) for binary aqueous solutions of sodium hexanoate, heptanoate, octanoate, decanoate, and dodecanoate salts at 25 °C. The diffusion coefficients of sodium hexanoate and heptanoate drop smoothly as the salt concentration is raised. For each of the longer-chain sodium alkanoates, D drops sharply in the region of the critical micelle concentration. Activity coefficient data are used to calculate resistance coefficients from the diffusion results. For aqueous sodium decanoate, micellar aggregation produces a 4-fold decrease in the friction acting on the diffusing salt. The mutual diffusion coefficient of aqueous sodium octanoate is compared with previously reported intradiffusion coefficients for sodium and octanoate ions.

A direct method is described for the correlation and comparison of sets of tracer (or limiting mutual) diffusion coefficients obtained under different conditions of temperature and density, which may or may not overlap, provided that at least one set has been obtained over a range of densities and temperatures. Recommendations are made for sets of diffusion data suitable for the calibration and cross-checking of high-pressure diffusion apparatus, particularly the Taylor dispersion (or chromatographic peak-broadening) apparatus.

Fischer-Tropsch synthesis employing supercritical fluid reaction media offers mass transfer advantages over conventional processes. Data are needed to calculate effective diffusivities in catalyst pores, for which molecular diffusion coefficients in the supercritical media as well as the catalyst porosity and tortuosity are required. The Taylor dispersion technique was used to measure the molecular diffusion coefficients. A tracer response technique was used to measure the effective diffusivities employing 1-octene in supercritical ethane (P{sub c} = 48.8 bar, {Tc} = 305.4 K) as the model system with an iron-based Fischer tropsch catalyst. Measurements were made in the temperature range of 523--543 K and pressure range of 62--144 bar. The results were analyzed by the subtraction of moments method. The precision of the results is within approximately 15%. The average value of tortuosity divided by particle porosity ({tau}/{epsilon}p) is, 9.72 {+-} 1.22, while the average value of {tau} is 6.10 {+-} 0.766 using the particle porosity set at 0.628.

Measurements of the mutual diffusion coefficient of the methanol/water system have been performed by using the Taylor dispersion technique. The results extend over the complete composition range for the mixtures and over the temperature range of 30-40°C. The system exhibits a minimum in the diffusivity as a function of composition at constant temperature, which is characteristic of alcohol/water mixtures

Diffusivities of propene measured at 298.2-348.2 K and up to 6891 kPa are reported for the solvents 1-butanol, chlorobenzene, ethylene glycol, and n-octane. Measurements were made by means of the Taylor dispersion technique. The densities of the solvents at the experimental temperatures and up to 6891 kPa are also reported

Diffusion coefficient measurements are required in a number of engineering applications and also in testing transport property theories. The diffusion coefficients of benzene, toluene, p-xylene, o-xylene, ethylbenzene, and mesitylene at infinite dilution in octane and in 2,2,4-trimethylpentane in the temperature range 303.2--333.2 K were determined by the Taylor dispersion technique. A correlation based on a free-volume-type expression represented the results to within experimental uncertainty.

The Taylor dispersion method has been used to determine diffusion coefficients of N-methylpyrrolidone, 2-methyl-2,4-pentanediol, glycerol, 1,3-butanediol, and 1,2,6-hexanetriol at infinite dilution in water and of water, glycerol, and 2-methyl-2,4-pentanediol at infinite dilution in N-methylpyrrolidone. The temperature has been varied between 298 and 348 K.

The Taylor dispersion technique was applied for the measurement of diffusion coefficients of dissolved gases in ethanol and toluene. Experiments with the system CO2 in H2O have been made to evaluate the accuracy of the method. The experimental procedure as described provides a fast and highly reproducible method for the determination of diffusion coefficients of dissolved gases in liquids. The diffusion coefficients of CO, CO2, and N2O have been determined in the temperature range of 298-333 K in ethanol and 298-348 K in toluene and of N2 in toluene at 298 K. There is a good agreement between the values as determined in the present work and available literature results at 298 K.

Binary diffusion coefficients of perylene, coronene, 12-crown-4 ether, 18-crown-6 ether, and (5,10,15,20-tetraphenyl-21H,23H-porphine)vanadiuun(IV) oxide in acetone, cyclohexane, and toluene were determined by the Taylor dispersion technique at 25 o C. The obtained diffusivities correspond to infinite dilution conditions

In this paper, the infinite dilution diffusion coefficients of poly(ethylene glycol) and poly(propylene glycol) in water were measured by using the Taylor dispersion technique. For poly(ethylene glycol), the measurements were performed in the temperature range of 303-318 K at four different polymer molecular weights. The diffusion coefficient was found to increase linearly with temperature bu decrease exponentially with molecular weight

We have utilized the Taylor dispersion technique to measure the infinite dilution mutual diffusion coefficients of 1-octene and 1-tetradecene in subcritical and supercritical ethane and in subcritical propane in the temperature range 293.15-338.15 K and the pressure range 5.52-11.03 MPa. For ethane, the measurements were done on either side of the critical temperature with the pressure above the critical pressure.

Taylor dispersion technique is used to measure the infinite dilution diffusion coefficients of eight solutes (H-/sub 2/, CO, CO/sub 2/, n-C/sub 8/H/sub 18/, n-C/sub 10/H/sub 22/, n-C/sub 12/H/sub 26/, n-C/sub 14/H/sub 30/, n-C/sub 16/H/sub 34/) in n-elcosane over the temperature range 100-260 /sup 0/C at 1.38 MPa pressure. The density and viscosity of n-elcosane were measured at the same conditions as well. It is shown that the rough hard-sphere theory can correctly represent the data.