Kinetic and thermodynamic parameters of volatilization of biodiesel from babassu, palm oil and mineral diesel by thermogravimetric analysis (TG)

Abstract

The boiling point and volatility are important properties for fuels, as it is for quality control of the industry of petroleum diesel and biofuels. In addition, through the volatility is possible to predict properties, such as vapor pressure, density, latent heat, heat of vaporization, viscosity, and surface tension of biodiesel. From thermogravimetry analysis it is possible to find the kinetic parameters (activation energy, pre-exponential factor, and reaction order), of thermally simulated processes, like volatilization. With the kinetic parameters, it is possible to obtain the thermodynamic parameters by mathematical formula. For the kinetic parameters, the minor values of activation energy were found for mineral diesel (E = 49.38 kJ mol⁻¹), followed by babassu biodiesel (E = 76.37 kJ mol⁻¹), and palm biodiesel (E = 87.00 kJ mol⁻¹). Between the two biofuels studied, the babassu biodiesel has the higher minor value of activation energy. The thermodynamics parameters of babassu biodiesel are, ΔS = −129.12 J mol⁻¹ K⁻¹, ΔH = +80.38 kJ mol⁻¹ and ΔG = +142.74 kJ mol⁻¹. For palm biodiesel ΔS = −119.26 J mol⁻¹ K⁻¹, ΔH = + 90.53 kJ mol⁻¹ and ΔG = +141.21 kJ mol⁻¹, and for diesel ΔS = −131.3 J mol⁻¹ K⁻¹, ΔH = +53.29 kJ mol⁻¹ and ΔG = +115.13 kJ mol⁻¹. The kinetic thermal analysis shows that all E, ΔH, and ΔG values are positive and ΔS values are negative, consequently, all thermodynamic parameters indicate non-spontaneous processes of volatilization for all the fuels studied.