ASOG method

UNIFAC andASOG Development. Pertinent equations of the UNIQUAC functional-group activity coefficient (UNIFAC) model for prediction of activity coefficients including example calculations are available (162). Much of the background of UNIFAC involves another QSAR technique, the analytical solution of groups (ASOG) method (163). 

K. Kojima and K. Tochigi, Prediction of Uapor-EiquidEquilibria by the ASOG Method, Elsevier and Kodansha Ltd., New York, 1979. 

A method was also developed to predict the parameters required for the NRTL equation the ASOG method, Kojima and Tochigi (1979). 

Kojima, K. and Tochigi, K. (1979) Prediction of Vapour-Liquid Equilibria by the ASOG Method (Elsevier). 

K. Kojima, K. Tochigi, Prediction of Vapor-Liquid Equilibria by die ASOG Method, Elsevier, Tokyo, 1979. 

The ASOG method would be impractical without electronic computers and appropriately designed programs. With these facilities available, the use of ASOG involves two essential steps ... 

By its thermodynamic nature the ASOG method can also be used to calculate polymer activities. Calculated activities in excess of one represent a definitely unstable phase condition and indicate phase splits. A method for an accurate description of liquid-liquid equilibria based on rigorous thermodynamics is given in Ref. 10. 

The ASOG method generates molecular or volume activity coefficients for each component in a mixture from a matrix of known pair interactions between each type of chemical group. Using the group counts in Table II and similar counts on the diluent, all permutations for interaction are calculated and properly weighted to give the solution activity coefficients. 

In the analytical solution of groups (ASOG) method of Derr and Deal [14], the four postulates of Wilson and Deal are implemented. The activity coefficient due to molecular size differences is given by the Flory-Huggins equation, Equation (4.414), and the group activity coefficient is given by the Wilson equation. 

The UNIFAC (universal functional activity coefficient) method [16] is similar to the ASOG method and is based on the four postulates of Wilson and Deal [13] regarding solution of groups. In UNIFAC, the activity coefficient is made of two parts. 

FIGURE 4.16 T-x-y phase diagram for benzene(l) -i- cyclohexane(2) mixtures at 1 atm calculated from UNIQUAC compared with data. (Kojima, K. Tochigi, K. Predictiou of Vapor-Liquid Equilibrium by the ASOG Method. New York Elsevier Scieutific Publishiug Co., 1979. With permissiou.)... 

The analytical-solution-of-groups (ASOG) method was developed by Derr and Deal17 and Wilson,72 and a compilation of parameters has been prepared by Kojima and Tochigi.41 In this method, the activity coefficient of component / in a mixture is computed as follows... 

The UNIFAC method, developed by Fredenslund et al.21,22 is similar in concept to the ASOG method, but it is based on the UNIQUAC equation... 

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