CONICET | Buscador de Institutos y Recursos Humanos

This chapter presents a study of the determination of free Methanol Content (MC) of Biodiesel (BD) by electrical properties (permittivity and conductivity) measurements and Flash Point (FP) determinations. International standards for BD characterization include MC and FP, since they are directly related to safety in production, storage and transport of biofuels. Moreover, measuremens of electrical properties, although at present are not included in international standards for BD characterization, can provide accurate information for the estimation of MC. Samples studied in this chapter were prepared by adding precisely known amounts of methanol (up to 2.5% V/V) to BD obtained from soybean oil and characterized according to international standards. High precision measurements of electrical properties were made from room temperature to 81ºC, in the frequency range between 20Hz and 2 MHz. In addition, FP was determined by the well known Pensky-Martens method, in accordance with standard ASTM D93. Measurements show a clear dependence of the permittivity and conductivity of the samples with MC. A linear model gives a good description of permittivity as a function of temperature and MC; particularly, the value of the real part of the permittivity extrapolated to 0ºC shows a linear dependence on MC. An excellent fitting to a potential function was found between MC and FP. Experimental data show that when the measured FP value is below the minimum indicated by the International Standards, MC exceeds the maximum allowable level. In summary, measurement of electrical properties and flash point determination are useful and convenient techniques for the verification of methanol content in biodiesel requiring simpler and less expensive equipment than chromatographic analysis.

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