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 the critical 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 chemical molecule with the critical data. The used structural information are small functional groups 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 molecular descriptors.

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 hydrocarbons 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 T_b= 329.250 K

Example calculation with molecular weight and atom count only

Used molecular weight: 58.080 ^g/_mol

Used atom count: 10

References