Katsumi Tochigi

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 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.

Prediction of high-pressure vapor-liquid equilibria using ASOG

Abstract A excess free energy mixing rule with Peng-Robinson EOS modified by Stryjek and Vera has been proposed in order to predict high-pressure VLE using low ASOG parameters. The mixing rule uses a zero-pressure excess free energy and the condition of quardratic composition dependence of second virial coefficient. Prediction is made for binary and ternary systems containing methanol, ethanol, water, and acetone at low and high pressures. With low-pressure ASOG parameters, high-pressure VLE have been predicted.

Prediction of vapor-liquid equilibria in non-polymer and polymer solutions using an ASOG-based equation of state (PRASOG)

Abstract An ASOG-based equation of state called PRASOG (Peng–Robinson ASOG) has been developed to predict vapor–liquid equilibria in non-polymer and polymer solutions. It makes use of the zero-pressure G E mixing rule consistent with the second virial coefficient condition for calculating the mixture parameters in Peng–Robinson EOS and predicts the G E using ASOG method. The first object of this paper is to predict low-pressure vapor–liquid equilibria (VLE) using PRASOG for 37 binary systems containing alcohols, hydrocarbons, ketones, esters, ethers, aromatic compounds and water. The PRASOG model has been then used to predict high-pressure VLE for ammonia-containing systems. In order to apply PRASOG to polymer solutions, PRASOG-FV has been proposed by calculating G E from ASOG-FV and VLE in polyisobutylene solutions have been then predicted.

Prediction of vapor–liquid equilibrium in polymer solutions using a Peng–Robinson group contribution model

Abstract The objective of this study is to extend the applicability of a Peng–Robinson group contribution method (PRASOG), which combines a zero pressure g E mixing rule for Peng–Robinson EOS with ASOG group contribution model, to polymer solutions. The solvent activities in polymer solutions have been predicted by PRASOG-FV which evaluates the g E from ASOG-FV proposed previously in order to predict the solvent activities in polymer solutions using ASOG group pair parameters. The systems discussed in this study are nine binary systems composed of six solvents (benzene, toluene, acetone, methyl ethyl ketone, ethyl acetate, propyl acetate) and four polymers (polystyrene, poly(ethylene oxide), poly(propylene oxide), poly(vinyl acetate)). The temperature range is 298.15 to 361.25 K. The accuracy using PRASOG-FV is almost comparable to those with ASOG-FV and UNIFAC-FV.

Determination of azeotropes in binary systems at reduced pressures

Abstract A method for determining azeotropes at reduced pressures is presented. An ebulliometer with fractionator is used for measurement, and azeotropic data are obtained for six homogeneous binary systems, namely ethanol - water, n-propanol - water, iso-propanol - water, methanol - benzene, ethanol - benzene, and acetone - methanol systems in the pressure range of 41.14 kPa to 101.32 kPa. Besides this, the same azeotropic data are predicted by ASOG group contribution method, and the predicted and experimental values show good agreement.

Measurement of Infinite-dilution Activity Coefficients of Alcohols in Water Using Relative Gas-liquid Chromatographic Method

Infinite-dilution activity coefficients of n-alcohols (C1-C8) in water were measured by using the relative gas-liquid chromatographic method proposed by Orbey and Sandler [1991]. The temperature range of measurement was 298 to 343 K. The g γ⋚ values at 298.15 K varied from 1.72 (methanol) to 1970 (n-heptanol). ASOG, UNIFAC, modified UNIFAC (Dortmund), modified UNIFAC (Lyngby) group contribution methods could predict γ⋚ to within 16.9, 28.8, 23.9 and 31.8 average percent error, respectively, for all systems and temperatures.

Prediction of ternary vapor-liquid equilibria by mixing rule containing regular solution and residual excess free energy terms

Based on a mixing rule, for the energy parameter > lda” in SRK equation, containing the geometrical mean of pure energy parameters and the residual part of the excess free energy at infinite pressure, vapor-liquid equilibria are predicted with good accuracy for 6 ternary systems consisting of polar and non-polar substances. The Wilson equation is applied to express the residual part of the excess free energy at infinite pressure. In addition, the significance of interaction coefficient kij of the conventional mixing rule is considered thermodynamically using the proposed mixing rule as the basis.

Prediction of non-polar gas solubilities in water, alcohols and aqueous alcohol solutions by the modified asog method

Abstract Tochigi, K. and Kojima, K., 1982. Prediction of non-polar gas solubilities in water, alcohols and aqueous alcohol solutions by the modified ASOG method. Fluid Phase Equilibria , 8: 221–232. The non-polar gas solubilities in water, alcohols and aqueous alcohol solutions are correlated and predicted by the modified ASOG method for a gas partial pressure of 1 atm and a temperature range of 10°C to 40°C. Solubilities in normal alcohols from methanol to octanol are considered. The non-polar gaseous solutes are oxygen, nitrogen, hydrogen, carbon dioxide, argon, methane, ethane, ethylene, propane and butane. The gas solubilities are first correlated and then predicted in pure solvents. Next, the gas solubilities are predicted for mixed solvents by using group pair parameters determined only from the data for gas solubilities in pure solvents. The deviation between the observed and the predicted gas solubilities is 6.0% in pure and 10.2% in mixed solvents.