Development of a new generalized correlation to characterize physical properties of pure components and petroleum fractions

A new generalized and non-group contribution method has been developed to predict critical temperature (Tc), critical pressure (Pc), critical volume (Vc) and acentric factor (ω) for pure substances and petroleum fractions based on two types of input parameters. This method can take either refractive index and molecular weight or refractive index and normal boiling point as its input. Since refractive index cannot be obtained for an unknown mixture (petroleum fraction), in order to apply the proposed method for petroleum fractions, refractive index is converted to mass density at 293 K using the one-third rule. Moreover, the proposed correlation is capable of predicting the properties using solely one input parameter such as molecular weight, normal boiling point or specific gravity, while the accuracy does not significantly change. In order to improve the accuracy of the proposed correlation, among the available 255 experimental data for pure substances and the 50 experimental data for petroleum fractions, about 70% was used for optimization and the rest was applied to validate the proposed correlation. The results of the predictions yielded by the proposed method are compared to those of the most conventional and most accurate reported methods in estimation of critical properties for pure substances and petroleum fractions. Comparison results indicate that the suggested correlation is simpler and more accurate than the other available methods. Furthermore, they can be applied in a wider range to estimate the properties of pure components, in comparison to the other relations.