Predicting the Enthalpy of Vaporization and Calculating the Entropy of Vaporization of 87 Octane Gasoline Using Vapor Pressure

Abstract

The vapor pressure (VP) of 87 grade gasoline was measured using an enhanced VP acquisition system over a temperature range of approximately 19.0˚C (292.2 K) and 69.0˚C (342.2 K). The empirical data were used to predict the thermodynamic entities the enthalpy of vaporization (ΔHvap) and the entropy of vaporization (ΔSvap) of gasoline. The results of this investigation yielded a ΔHvap value of 35.1 kJ/mol and ΔSvap of 102.5 J/mol∙K. The value of ΔHvap was in excellent agreement with the findings of a prior study (Balabin et al., 2007), which produced a ΔHvap values of 37.3 kJ/mol and 35.4 kJ/mol. The enthalpy and entropy of vaporization of n-heptane (37.2 kJ/mol and 100.1 J/mol∙K) and n-octane (39.1 kJ/mol and 98.3 J/mol∙K) were also determined after acquiring VP data for the two VOCs. The empirical results for n-heptane and n-octane were also in excellent agreement with the literature. These favorable comparisons strengthen the capacity of our system for acquiring the VP data for pure and volatile multi-component mixtures.