Determinación de la estabilidad de la mezcla de etanol con naftas mediante la medición de sus propiedades dieléctricas y refractométricas

Abstract

Introduction— The use of the ethanol mixtures with gasoline or naphtha has the problem of this mixture’s natural tendency to separate in two phases, since the ethanol is a substance formed for polar molecules, while that in the naphtha they are non-polar. Completes miscibility of the ethanol in the naphtha is strongly dependent upon the molecular interactions among these molecules of different polarities and the determination of the dielectric constant and the refraction index gives valuable information about these molecular interaction’s.

Objective— Determination of the ethanol-naphtha mixtures stability using measurement technologies of the dielectric constant and the refraction index.

Methodology— Digital LCR meter with cylindrical capacitive cells and Abbe’s refractometer are used for these measurements with a high precision and they permit to characterize to the ethanol mixtures with hydrocarbons in all the practical- applications range.

Results— They results were obtained with the mixtures of anhydrous- ethanol with three Cubans naphtha: the Reformed Naphtha (NR), the Light virgin Naphtha (NVL) and the Heavy Virgin Naphtha (NVP), which conform the distinct gasoline types used in Cuba. The experimental results are correlated with a thermodynamic study of mixture’s stability, using Gibbs’s free energy.

Conclusions— It is clear that the mixture of ethanol with NR is more stable than NVL and NVP, besides one proves that to a concentration of 15% of ethanol its vaporization enthalpy remains underneath the gasoline, for it that the ethanol once was added does not decrease the efficiency of the combustion for this concept to the mixture in the evaporation and combustion process.