Kazuo Kojima

Measuring methods of infinite dilution activity coefficients and a database for systems including water

Experimental techniques for the determination of infinite dilution activity coefficients and their improvements are reviewed. Generally, the measuring techniques can be classified as the indirect and direct methods. The indirect methods include the extrapolations from vapor-liquid equilibrium data and calculations from the other thermodynamic data, such as liquid-liquid equilibrium data, gas-liquid partition coefficient data and so on. The direct methods include the gas-liquid chromatography (GLC) method, headspace GLC method, gas-stripping method, liquid-liquid chromatography method, differential ebulliometry method and differential static method. Also, the most extensively used gas-liquid chromatographic method can be divided into the stationary phase GLC, non-steady-state GLC and relative measurement GLC. A database of infinite dilution activity coefficients, which had been measured and reported by 96 literature sources of journals in the period from 1927 through 1995 for organic compounds in water and water in organic solvents, has also been presented. The database contains a total of 1469 pieces of data of infinite dilution activity coefficients ranging from 283.15 to 373.15 K. No database of infinite dilution activity coefficients for systems including water has been previously reported.

Prediction of critical points in multicomponent systems using the PSRK group contribution equation of state

Abstract This paper describes a procedure and first results for the prediction of critical points of nonideal systems with a UNIFAC-based equation of state. The PSRK group contribution model (Holderbaum and Gmehling, 1991) was incorporated in the computational method developed by Heidemann and Khalil (1980). The algorithm was extended on testing both local and global thermodynamic stability of calculated critical points. Predicted critical points of 15 binary systems were compared with experimental data. The test mixtures included aqueous solutions of inorganic gases, hydrocarbons, alcohols and carbon dioxide. Excellent agreement was obtained in cases when experimental VLE data covered a wide range of temperatures and pressures. For complex systems, a correlation method was suggested which may be useful to improve the predictive ability of group contribution methods for supercritical mixtures. Multicomponent critical points were predicted for 36 systems containing three to twelve components. The PSRK results were compared with the performance of the original SRK and SPHCT equations of state (Garcia-Sanchez et al., 1992).

Prediction of infinite dilution activity coefficients in aqueous solutions by group contribution models. A critical evaluation

Abstract Based on an extensive database, the predictive accuracy of the ASOG and several UNIFAC-type models has been critically evaluated for infinite dilution activity coefficients in aqueous solutions. In general, all the models give rather poor results with mean relative deviations of 45–72% (except the cases where the relative deviations are higher than 100%), whereas the modified UNIFAC (Dortmund) performs well for most of higher polar compounds (e.g., ethanol, acetone, acetic acid) in water mixtures. The UNIFAC–LLE of Magnussen et al. may provide order of magnitude estimates for some lower polar compounds (e.g., aldehydes or 2-ketones with carbon number of 6–9), although it gives poor results for the higher ones. In the particular case of alkanes in water mixtures, the specially developed model of Hooper et al. provides comparatively fair results, but the predicted mean relative deviations of 36% are still large. In this work, an improved UNIFAC will be proposed by using mixture-type groups to account for the specially hydrophobic effects in systems including water, satisfactory results are obtained.

Measurement and correlation of liquid-liquid equilibria up to critical solution temperature

Abstract An apparatus for measuring the mutual solubility curve of binary systems at moderate pressures is presented which is composed of an equilibrium cell made of pressure glass with film heaters and a light sensor. The formation or disappearance of turbidity has been confirmed by the intensity of the scattered light, which is monitored by a computer via digital multimeter. The measurement of temperatures was made with a platinum resistance thermometer. This technique was examined for measuring the mutual solubilities in the range of room temperature to the critical solution temperatures on the binary systems; butanol ∼ water, ethyl methyl ketone ∼ water, butyl cellosolve ∼ water and diethylene glycol ∼ benzene. The experimental results of the mutual solubilities were correlated by the NRTL equation.

A note on a modified Huron-Vidai mixing rule consistent with the second virial coefficient condition

Abstract Using the procedure by Wong and Sandler (1992), zero pressure mixing rules for cubic equations of state can be made consistent with the quadratic composition dependence of the second virial coefficient. The MHV1 mixing rule extended on the second virial coefficient condition has been applied to 6 binary and 3 ternary systems. No significant differences have been observed from predictions of the original MHV1 model which uses the linear mixing rule for equation of state parameter b .

Measurement of vapor-liquid equilibria and determination of azeotropic point

Abstract Hiaki, T., Tochigi, K. and Kojima, K., 1986. Measurement of vapor—liquid equilibria and determination of azeotropic point. Fluid Phase Equilibria , 26: 83–102. To measure the azeotropic point, a liquid-vapor ebullition type equilibrium still is developed. Vapor-liquid equilibria at 101.325 kPa are measured for the ternary azeotropic system benzene - cyclohexane - n-propanol, and the three constituted binary azeotropic systems. A method is introduced for graphical determination of the binary azeotropic point on the basis of experimental binary vapor-liquid equilibrium data. Also, a method is evolved for determination of the binary and ternary azeotropic points by using the extended Redlich-Kister equation applicable to the condition of constant pressure, and the azeotropic points are determined for three binary and one ternary systems.

Measurement of vapor-liquid equilibrium for systems with limited miscibility

Abstract A method for measuring isobaric vapor-liquid equilibrium data for binary systems with limited miscibility is presented. The method involves of the determination of the dew-point isobar, the bubble-point isobar, and the liquid-liquid equilibrium at bubble-point. The dew-point isobar was determined by means of a vapor mixing method. The bubble-point isobar and the miscibility gap were determined by an ebulliometric method. Measurements were made for the binary systems methyl ethyl ketone - water, water - methyl isobutyl ketone and water - n-butylacetate, at 760 Torr. The experimental VLE data were checked for thermodynamic consistency by means of the generalized Gibbs-Duhem equation and correlated by the modified Redlich-Kister equation.

Measurement and correlation of vapor-liquid equilibria in polymer solutions containing polystyrene with polymer ASOG

A gas chromatographic method is used to measure the activities of solvents which have a range of finite concentrations in polymer solutions. Experimental data are presented for 8 binary solvent/polystyrene systems at 393.15 and 423.15 K. The polymer ASOG is proposed to be correlated with the activities of solvents in polymer solutions, and consists of the original ASOG and the empirical modification of free volume. For 8 binary solvent/polystyrene systems containing nonpolar and moderately polar solvents, the polymer ASOG was successful to correlate with experimental data within the range of 1% error.

Determination and correlation of LLE and SLE data for the system aniline+cyclohexane

A newly developed laser light scattering technique was used for the determination of mutual solubilities in the aniline+cydohexane system at moderate pressures. The liquid-liquid equilibria (LLE) were measured from the region of solid-liquid equilibria (SLE) to the upper critical solution temperature. Freezing points in this system were determined by a cooling curve method. The solubility data were correlated with the NRTL equation.

Thermodynamic consistency test of vapor—liquid equilibrium data—alcohol—hydrocarbon systems

Abstract The thermodynamic consistency test of vapor—liquid equilibrium data has been carried out for 224 data sets—101 isobaric and 123 isothermal sets—of 35 binary alcohol—hydrocarbon systems by using the method proposed in our earlier work. The method permits an overall check of data by using three tests: a point test, an area test and an infinite dilution test. The consistency test gave the result that 60 data sets among 224 were reliable.