- Klincewicz method
The Klincewicz method [Klincewicz K. M., Reid R. C., "Estimation of Critical Properties with Group Contribution Methods", AIChE Journal, 30(1), 137-142, 1984] is a predictive method based both on group contributions and on a
correlation with some basic molecular properties. The method estimates thecritical temperature , the critical pressure, and the critical volume of pure components.Model description
As a
group contribution method the Klincewicz method correlates some structural information of a chemicalmolecule with the critical data. The used structural information are smallfunctional group s which are assumed to have no interactions. This assumption makes it possible to calculate the thermodynamic properties directly from the sums of the group contributions. The correlation method does not even use these functional groups, only the molecular weight and the number of atoms are used as moleculardescriptor s.The prediction of the critical temperature relies on the knowledge of the normal boiling point because the method only predicts the relation of the normal boiling point and the critical temperature and not directly the critical temperature. The critical volume and pressure however are directly predicted.
Model Quality
The quality of the Klincewicz method is not superior to older methods, especially the method of Ambrose [Ambrose D., "Correlation and Estimation of Vapour-Liquid Critical Properties. I. Critical Temperatures of Organic Compounds", Nat.Phys.Lab.Rep.Chem., Rep.No. NPL Rep.Chem. 92, 1-35, 1978] gives somewhat better results as stated by the original authors and by Reid et al.Reid R.C., Prausnitz J.M., Poling B.E., "The Properties of Gases & Liquids", Monograph, McGraw-Hill, 4 Ed., 1-742, 1987] The advantage of the Klincewicz method is that it is less complex.
The quality and complexity of the Klincewicz method is comparable to the Lydersen method [Lydersen A.L., "Estimation of Critical Properies of Organic Compounds“, University of wisconsin College Engineering, Eng. Exp. Stn. Rep. 3, Madison, Wisconsin, 1955] from 1955 which has been used widely in chemical engineering.
The aspect where the Klincewicz method is unique and usefulReid R.C., Prausnitz J.M., Poling B.E., "The Properties of Gases & Liquids", Monograph, McGraw-Hill, 4 Ed., 1-742, 1987] are the alternative equations where only very basic molecular data like the molecular weight and the atom count are used.
Deviation diagrams
The diagrams show estimated critical data of
hydrocarbon s together with experimental data [Dortmund Data Bank ] . An estimation would be perfect if all data points would lie directly on the diagonal line. Only the simple correlation of the Klincewicz method with the moelcular weight and the atom count have been used in this example.Equations
Klincewicz published two sets of equations. The first uses contributions of 35 different groups. These group contribution based equations are giving somewhat better results than the very simple equations based only on correlations with the
molecular weight and the atom count.Group contribution based equations
T_c , = , 45.40 - 0.77 * MW + 1.55 * T_b+sum_{j=1}^{35} n_j Delta_j
MW/P_c)^{1/2} , = , 0.335 + 0.010 * MW + sum_{j=1}^{35} n_j Delta_j
V_c , = , 25.2 + 2.80 * MW + sum_{j=1}^{35} n_j Delta_j
Equations based on correlation with molecular weight and atom count only
T_c , = , 50.2 - 0.16 * MW + 1.41 * T_b
MW/P_c)^{1/2} , = , 0.335 + 0.009 * MW + 0.019A
V_c , = , 20 + 0.088 * MW + 13.4 * A
with
*used normal boiling point Tb= 329.250 K
Example calculation with molecular weight and atom count only
Used molecular weight: 58.080 g/mol
Used atom count: 10
References
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