Influência da temperatura na resistividade elétrica de biodiesel e óleo diesel

Abstract

In order to meet the National Petroleum Agency’s (ANP) requirements, when talking about the amount of biodiesel in diesel-biodiesel (DB) mixtures, the Agency takes FT-IR as a standardize methodology. However, alternative methodologies have been developed and are used to carry out such quantification, with the objective of improving detection limits, simplifying measurement alternatives, as well as decreasing the costs involved in the process. Electrical properties of oleaginous materials have been studied for some time by our research team, aiming the use of techniques that involve such systems in the quantification of the biodiesel that exists in DB mixtures. In this work, the electrical resistance was determined by the continuous flow current technique (DC characterization), for which a cell was specifically built, consisting of two parallel metal plates, connected to an electric voltage source and to an electrometer. In order to analyze and describe the samples, they were loaded in beaker and heated into a heating plate. The current-voltage data was obtained in 10 °C intervals from room temperature up to a temperature of 110 °C. The samples utilized were diesel oil, commercial soybean oil and biodiesel, the last one produced from the chemical reaction of transesterification, using methanol and soy oil as raw material. The approximate values obtained for the electrical resistance at room temperature were 1.3 × 1011 Ω.cm for biodiesel, 4.7 × 1011 Ω.cm for diesel and 1.1 × 1012 Ω.cm for soybean oil. The results were compared with the values referenced in the literature for oleaginous materials, being coherent within the order of magnitude for this type of material. Finally, an Arrhenius-type behavior was observed when a dependence of the electrical resistance was evaluated as a function of temperature, being found values of noticeable energy activation of 0.11 eV, 0.21 eV and 0.26 eV for biodiesel, diesel and soybean oil, respectively.