ACCURATE SIMULATIONS OF THE VAPOR-LIQUID-EQUILIBRIUM OF IMPORTANT ORGANIC-SOLVENTS AND OTHER DIATOMICS

The vapor-liquid equilibria of 20 substances, most of them widely used as organic solvents, were obtained by means of a Gibbs ensemble Monte Carlo method. All these substances can be represented by linear or an gular models with only two bonds. The intermolecular interaction was d escribed by a Kihara potential and, where appropriate, an additional m ultipolar potential using meaningful microscopic parameters. The resul ts agree excellently with experiment even for ranges of hundreds of ke lvin when potential parameters are obtained only from fitting two crit ical constants. The largest discrepancies are observed for liquids cap able of forming hydrogen bonds, especially alcohols, but even in these cases agreement is very fair for temperature-density equilibrium bell s. Agreement is also very good for vapor pressure up to close to criti cal pressure, namely 60-80 bar in all cases. The worst agreement is ag ain observed for hydrogen-bonding liquids. Vaporization enthalpies wer e also calculated for some substances. In this case agreement was only fair but also over a large range of temperatures. Finally, parameters commonly used in chemical engineering, such as the acentric factor an d solubility factor, which enable prediction of the mutual solubilitie s of some hundreds of mixtures, were calculated. Some of these mixture s are not yet apparently measured in spite of their possible industria l interest.