Extending the group contribution concept using kihara potential to perfluorinated n-alkanes CnF2n+2 (n = 1–6) for estimating thermophysical properties

The concept of the group contribution using Kihara intermolecular potentials with a spherical core is extended to perfluorinated n-alkanes (n = 1–6). The effective Kihara parameters for groups (CF2, CF3, CF4) are estimated by fitting second virial coefficient B and dilute gas viscosity η together. The assumption of regarding CF4 molecule as a single group is preferable to other two approaches based on the principle of group additivity: a combination of F–(CF3) and CF3–(F) groups; a single C–(F)4 group and four F–(C) groups.Application of the model shows that second virial coefficients are represented with better results than those of the Tsonopoulos correlation, and are comparable to the correlation of Dymond's group and the Hohm correlation. Feasibility of the present method to calculate dilute gas viscosities is proved by comparison with the Lucas method, the Hohm correlation, the correlation of Yaws, and the Simsci Data Bank. Mixture property calculations of the model are enhanced by including binary group interaction coefficients kij,gc, determined from second cross virial coefficient data, and are more reliable than other correlations for second cross virial coefficients and mixture viscosities. Prediction results of binary diffusion coefficients, not supplied to the parameter evaluations, are in significant agreement with experimental data and are compared well with values obtained by means of the Fuller method. Results studied here would be of use when extended to halogenated paraffins and their mixtures.