Biodiesel fuel formulation


World energy consumption rises every day and, inversely, fossil fuel resources are dwindling day by day. Transportation sector is the bigger consumer of oil. Faced with the actual scenario a renewable and sustenable alternative is needed, not just to decrease our dependence of petroleum but also to base our power in a renewable source. Biodiesel is at the forefront of the alternatives to petroleum based fuels in the transportation sector, being considered an important short-time option since its price can be competitive with conventional diesel and no motor changes are required. Biodiesel consists on a liquid blend of, non toxic, biodegradable fatty acid esters, with non sulfur and aromatic content, good lubricity, high cetane number, nontoxic character of their exhaust emissions and cleaner burning. Aiming at tuning biodiesel to optimize the fuel composition, the present work contributes for a better knowledge of de depencende of thermophysical properties of biodiesel on their compositon. New data is required to help in the development of reliable models to predict biodiesel behavior. Density and viscosity data are a mirror of biodiesel composition, as both depend on the raw material, more than the production process. New data of density and viscosity were measured and respective models were tested and compared, and new adjusted parameters proposed for this family of compounds. The measured data include a wide range of temperatures and in the case of density data were also measured at high pressure for biodiesel and some pure methyl esters. This work also reports experimental data for the solid-liquid-phase equilibria of biodiesel and, liquid-liquid equilibria of some important systems in biodiesel production. Both type of equilibria were described with models developed in our laboratory. A special importance is here given to properties that depend on fatty acid profile of raw material besides density and viscosity; the iodine value, and cold filter plugging point are here evaluated based on norm considerations. Free Fatty Acids (FFA) are a by-product in edible oil refining, that are removed in the deodorizing step on oil purification. Enzymatic catalysis is here studied as an alternative to convert this by-product into biodiesel. The ability of immobilized lipase from Candida antartica (Novozym 435) to catalize the esterification of FFA with methanol and ethanol were evaluated using response surface methodology with an experimental design. Influence of several variables were evaluated in the yield of reaction.


Maria Jorge Pratas

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João Coutinho and Sílvia Carriço Monteiro



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