Avaliação da estabilidade oxidativa de misturas binárias de biodieseis metílicos obtidos a partir de óleos de soja, algodão, canola, girassol, milho e residual

Abstract

The diversity of sources for biodiesel production provides the acquisition of the products with different chemistry compositions and properties. In order to the standardize the product, the National Agency of Petroleum, Natural Gas and Biofuels (ANP), regulates the use and commercialization of biodiesel. Among the main properties controlled by ANP in order to ensure the quality and time of storage of biodiesel stands out the oxidation stability. In this sense, this work showed the study of behavior and efficiency of biodiesel compared to binary blends oxidative stability. The biodiesels was performed using the transesterification reaction for methylic route and base catalyst from refined soybean oils, canola, sunflower, corn, cotton and also residual. The most important physical-chemistry properties was determined, included acid index, saponification index, oxidation stability, specific gravity, kinematic viscosity, flash point, moisture, free and total glycerin, iodine index and peroxide index. The biodiesels analyzed was according to the proposed for the specifications regulated for ANP, expect the oxidation stability of biodiesel of sunflower, residual and cotton (period lower of 6h). The binary blends was prepared using soy biodiesel (BMS), canola (BMC), sunflower (BMG), corn (BMM), cotton (BMA) and residual (BMR) and oxidation stability was determined for Rancimat method. The BMS contributed to the improvement of the oxidative stability of the BMA, BMG and BMR. When the BMM and BMC were added to the BMS, this showed major value for the induction period (PI). It was observed that the smaller the concentration of polyunsaturated (AGPs) fatty acids, the greater the value of PI. The dates obtained at study of blends allowed relate the oxidation stability with other properties (peroxide and iodine index). It was verified that the improvement of peroxide index followed the same growing order of concentration the AGPs, so the BMG exhibited the higher value for peroxide index, higher concentration of the AGPs and lower value for the PI. The analysis of the iodine index was realized and the results were allowed with the PI, APGs and peroxide index for the all biodiesels.