Regression equations of the biodiesel permittivity from its composition, molecular structure, and temperature

Abstract

The measurement of electrical permittivity (EP) has been used in many biodiesel (BD) studies. They include the characterization of different oil-based BD and its blends with diesel fuel (DF), its adulteration with vegetable oils (VOs), the estimation of the kinematic viscosity and the BD content in its blends with DF, the evaluation of the purification process efficiency after the reaction of transesterification, and the detection of BD aging and fuel quality control. A few hundreds of VOs have the potential for BD production, and their experimental EP values for most of them are not currently known. The EP of BD as a function of its fatty acid methyl ester content and molecular structure is determined in this work using regression equations. A regression analysis was performed using experimental databases for the EP, which included a total of 43 data points in the range of 20–50 °C. The equations were derived using multiple linear regression analysis and accurately reproduced the BD EP’s dependence on the carbon chain length and unsaturation level. When the regression equations’ results were compared to available experimental data, they showed a high level of agreement. The EP equations’ RMSE values utilizing all of the data were lower than 0.038.