A Simple Generic Model for Estimating Saturated Vapor Pressure

Abstract

Arguably, the most important of the basic thermodynamic properties of fluids, vapor pressure has been the focus of investigation for over a century. The two main drawbacks of the models currently used for its correlation are that they either exhibit large deviations near critical temperature and triple point or that they have a large number of compound-specific adjusted parameters and hence the inconvenient necessity of having at hand large tabulations of hundreds of model parameters. In this study, by employing the up and coming procedure of genetic programming, a new model, which to a large extent remedies these shortcomings, is proposed. Essentially, having only two compound-specific adjusted parameters and also using two readily available substance parameters of molecular weight and normal boiling point ensure a high level of convenience, yet precision and applicability over a large portion of the vapor–liquid coexistence curve. Concisely, a sizable database comprised of 58,272 data points was gathered for 243 organic and inorganic compounds and elements belonging to a diverse set of chemical families; these were then used in both developing and validating the proposed model and reporting generic and compound/element-specific adjusted parameters. Average absolute relative deviations (AARDs) of 1.47% (for a subset of 40,852 data points) and 1.82% (for a subset of 17,420 data points) for the general model and a slightly modified model applicable to hydrogen-bonded alcohols and phenols, respectively, are a testament to the reliability of the new proposed model.