Surface Tension Prediction of n-Alkanes by a Modified Peng-Robinson Equation of State Using the Density Functional Theory

Abstract

Through this study, the ability of a modified Peng-Robinson (MPR) equation of state in predicting the surface tension of n-alkanes based on the density functional theory approach was investigated and compared with other studies. The interfacial layer thickness and the density profile were calculated simultaneously at different temperatures from triple point to near critical point using the modified Peng-Robinson equation of state. It was shown that the calculated thickness of interfacial layer increases with decrease in the chain length of n-alkanes molecules and raising of temperature. The surface tension of n-alkanes was calculated using the calculated values of thin layers’ densities. It was shown that the calculated surface tension of n-alkanes decreases with temperature in accordance with the experiment. The average relative error in prediction of the surface tension by the MPR equation of state was in the range of 2.5-6% while it was 4.6-25.2% by the Peng-Robinson equation of state. The validity of the MPR equation of state in the surface tension prediction of n-alkanes containing C1-C10 has been proved by comparing the results of this work with other studies.