Relations Between the Properties Required by International Standards and Dielectric Properties of Biodiesel

Abstract

The measurement of two properties of biodiesel, flash point (FP) and methanol content (MC) is among the requirements to verify the conformance of the final product to international standards. In this chapter the relation between FP and MC and electrical properties (EP) will be discussed. It is important to remark that the measured flash point value, at the maximum methanol content set by all international standards, corresponds to the minimum allowable flash point according to most international standards. Therefore, compliance with the FP requirement is also a good indicator of compliance with maximum MC. Given the strong correlation between MC and FP, it is possible to use FP measurements for the preliminary verification (prior to certification) of the compliance with the methanol content requirements set by biodiesel standards. This is relevant since FP measurements are much simpler and use less expensive equipment than the procedure for determination of methanol content recommended by standards (chromatographic analysis). Moreover, measurements of electrical properties (EP) carried out at different temperatures show a clear dependence between MC and the permittivity and conductivity of the samples. Therefore, permittivity measurements as a function of temperature makes possible to determine accurately MC in biodiesel within a wide range of concentrations, including the maximum value set by the standards (0.2%). Also, measurements of biodiesel conductivity at room temperature (25°C) may be used for a preliminary check of methanol concentrations above 0.5%. In summary, although they are not required by international standards, EP measurements provide a convenient, low-cost alternative for the verification of the required parameters.