Correlations of surface tension for mixtures of n-alkanes as a function of the composition: applicability and performance analysis of existing models.

Abstract

In this work, a large data set of experimental values of surface tension for binary mixtures of two n-alkanes have been compiled. These values are later fitted to different models of correlation as functions of molar fraction at various temperatures. All of these models use the surface tension of pure fluids as input data and may require between one and three adjustable coefficients. For some mixtures and/or temperatures, where the surface tension values of pure fluids have not been measured, predictions from previously proposed specific correlations for pure fluids are considered as an alternative. Different cases are studied accordingly with the availability of surface tension values for pure fluids: (i) available for both pure fluids, (ii) available for only one of the fluids, and (iii) unavailable for both fluids. Moreover, a fourth case is considered to include those mixtures and temperatures at which one of the fluids is supercritical. The applicability and accuracy of 10 different analytical correlation models are evaluated based on the percentage deviations between experimental and calculated values. Additionally, the Akaike Information Criterion is applied to identify the most suitable models. As a main result, it is found that predicted values from correlations for pure fluids can be used instead of experimental data without significantly affecting the accuracy and applicability of the models. Moreover, it is shown that the Winterfeld-Scriven-Davis model, which has a certain physicochemical basis and only one adjustable coefficient, provides the best overall results. However, this model cannot be applied when one of the fluids is supercritical and its surface tension is assumed to be zero. In this case, the Redlich-Kister correlation, with two or three adjustable coefficients, provides better results. More recent or more complex models are not necessary to achieve excellent accuracy for n-alkane mixtures and therefore should be avoided.