Efeitos de contaminantes metalicos na estabilidade oxidativa e o uso de antioxidantes naturais em biodiesel de soja

Abstract

Biodiesel stands out for being considered a lower environmental impact fuel, biodegradable, made from renewable sources and less polluting than diesel. Despite of many advantages cited, the biodiesel s chemical nature makes it more susceptible to oxidation when compared to mineral diesel fuel during production, transport and storage. This biofuel has a high level of reactivity with oxygen, especially when placed in contact with metal surfaces, the presence of air, moisture, light and heat or even environments contaminated by microorganisms, thereby undermining its features. The biodiesel quality is designated for three standards EN 14214, ASTM D - 6751 and ANP 45/2014, and oxidative stability is among the parameters monitored by these regulations. The aim of this study was to evaluate the oxidative stability effect of biodiesel B100, obtained from soybean oil (Glycine max) by methyl route, compared to some metal contaminants and the effect of the concentration of these, as well as evaluating the pollen potential and propolis as natural antioxidants in biodiesel. To do this seven different concentrations were prepared in the range of 0.5 to 3.5 mg L-1 with an increment of 0.5 mg L-1 of different types of ions (Fe, Cu, Co, Mn, Zn, Cd, Ni , K, Pb, Cr) and applied the statistical test ANOVA with two-factor and one factor. It also examined the effect of three different types of natural antioxidants (pollen, brown propolis and green propolis) in 6 different concentrations. The oxidative stability analyzes were performed according to EN 14112. From these tests it can be seen that the quality of biodiesel decreases in the presence of some metals. Generally, the metals that achieved worst results were Cu, Co, Cr and K, which effects obtained above 10%. Then Pb, Zn, Mn and Ni with effect from 5 to 10% and finally the metals Fe and Cd, which showed smaller effects on oxidative stability of biodiesel, with results below 5%. Related to the natural antioxidants green propolis was the additive that had the best result, upon reaching the 0.5 % v/v concentration efficiency was for 23%, followed by brown propolis and pollen, both with 15% effect, this same condition. For biodiesel doped with cobalt ion to 0.5 mg L-1 propolis together with the antioxidant at a concentration 0.50%, showed a gain in stability on the order of 30%.