Enthalpies of vaporization of petroleum fractions from vapor pressure measurements and their correlation along with pure hydrocarbons

Enthalpies of vaporization for 58 petroleum fractions were obtained from the measurement of vapor pressures at various temperatures by using an inclined ebulliometer with a pump-like stirrer on the basis of the principle of the quasi-static method. Some existing methods for predicting the enthalpies of vaporization of pure hydrocarbons at the normal boiling temperature were tested to calculate those of the petroleum fractions. It was observed that these methods gave reasonable results only for the lower and middle petroleum fractions and had relatively large deviation for the heavier fractions. A new equation based on the normal boiling temperature, the molecular weight and specific gravity as input parameters has been developed, which is particularly suited for calculation of the enthalpy of vaporization of hydrocarbons (C3–C30) and petroleum fractions in a wide boiling point range from 231.1 to 722.8 K.