Evaluation of the thermal properties of diesel oil with low sulfur content

The presence of sulfur in diesel causes environmental pollution and corrosion of engines. In order to minimize the consequences of this pollutant, Brazilian laws established the maximum of sulfur content that diesel fuel may contain. To meet these requirements, diesel with a maximum sulfur concentration equal to 10 mg kg−1 (diesel S10) has been widely marketed in the country. The reduction in sulfur leads to changes in the physicochemical properties of the fuel, which are essential for the performance of road vehicles. This work aims to evaluate the reduction in the sulfur content in diesel fuel using thermogravimetry. Samples of diesel types S10, S500 and S1800, corresponding to 10, 500 and 1800 mg kg−1 of sulfur content, respectively, were tested according to ASTM methods for specific gravity, flash point and sulfur content. Then, these fuels were characterized by thermogravimetry from room temperature up to 500 °C, in helium flow, at heating rates of 5, 10 and 20 °C min−1. TG and DTG data showed a typical mass loss at ca. 40–320 °C, due to volatilization or distillation of light and medium hydrocarbons. Based on these data, the kinetic behavior of the samples was analyzed and the activation energies (Ea) for decomposition of the samples decreased in the order: S1800 > S500 > S10.