Pure-component vapour pressures of heavy hydrocarbons containing nitrogen or sulphur using the UNIFAC group-contribution method

A group-contribution model for predicting pure-component vapour pressures, in part based on the UNIFAC method for vapour—liquid equilibria, has been extended to include hydrocarbons of molecular weights below 500 containing nitrogen or sulphur. Good representation is obtained for vapour pressure data in the region 10–2000 mmHg. In addition, the accuracy of the method is tested by prediction of heats of vapourization via the Clausius—Clapeyron equation. The predicted heats of vapourization agree with the experimental values within a few percent. In absence of experimental data, the model may be used to estimate vapour pressures and heats of vapourization for the category of compounds studied.