On the Calculation of Surface Tensions of n-Alkanes Using the Modified SAFT-BACK-DFT Approach

Pressure–Surface Tension–Temperature Equation of State for n-Alkanes

Herein, the geometric similitude concept is applied to propose a cubic equation that relates surface tension, saturation pressure, and temperature for n-alkanes. The input properties for each fluid are the molecular mass, pressure, temperature, and compressibility factor at the critical point. The model is applied to temperatures below 0.93·T_c (critical point temperature). A total of 2429 surface tension values have been selected for 32 n-alkanes. The parameters of the model have been obtained with a fit of the surface tension values for 19 pure n-alkanes that are randomly chosen. Then, it is tested for the other 13 pure n-alkanes and used to predict the surface tension for 11 binary and 4 ternary mixtures. These predictions are compared with the reported experimental data. For pure n-alkanes, the overall absolute average deviation is 2.4%, including the correlation and testing sets. No additional adjustable coefficients are used for mixtures, yielding an overall absolute average deviation of 2.98% for the binary systems and 7.97% for the ternary ones. The results show that the model is accurate enough for predictions and that the highest deviations are due to the lack of agreement in the values of surface tension of pure fluids obtained from different sources.