Vapor-liquid equilibrium data evaluation for systems of interest in the biodiesel production
Vapor-Liquid Equilibria, Soybean Oil, Ethanol, Biodiesel.
In an attempt to mitigate the environmental impacts arising from the burning of fossil fuels, many studies have sought to make biodiesel production even more feasible, since it is a renewable, biodegradable fuel that has a lower content of polluting compounds. In this sense, this work studies the liquid-vapor equilibrium of three systems that are of interest to the biodiesel industry. The system formed by ethanol (1) and oleic acid (2) with isobaric data at 760 mmHg, isothermal at 318.15 K and activity coefficient at infinite dilution; the system formed by n-hexane (1) and cottonseed oil (2) with isobaric data at 310 mmHg and the system formed by ethanol (1) and soybean oil (2) with isobaric data at 760 mmHg and 600 mmHg. For this, a thermodynamic modeling was carried out with the ideal (Raoult's Law), UNIQUAC correlation and UNIFAC prediction approaches. The vapor pressure data of the pure substances were extracted from the literature. Antoine's constants for ethanol, oleic acid, n-hexane, cottonseed oil and soybean oil, showed relative mean deviations of, respectively, 0.34%, 3.30%, 0.55%, 5.00% and 2.53%. The γ∞ values and binary data for the ethanol and oleic acid system were extracted from the literature. For the other systems, binary data were obtained in a modified Othmer ebulliometer. The correlation study with the UNIQUAC model described with quality the behavior of all systems under the conditions of interest. The predictive study carried out with the UNIFAC model showed small deviations in relation to the UNIQUAC model. For all systems, a deviation from ideality was observed.