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METROLOGICAL EVALUATION OF TITRATION TECHNIQUES FOR THE DETERMINATION OF THE IODINE VALUE IN BIODIESEL

01/2008;

ABSTRACT Based on international standard procedures, the degree of unsaturation on biodiesel was evaluated, called iodine value. Two titration techniques were used to determine the iodine value: colorimetric and potentiometric techniques. The uncertainty of measurement was used to evaluate the quality of the results. The potentiometric technique showed better quality in the determination of the iodine value because of its accuracy as well as lower uncertainty result of the measurements, with values between 0,613 g I2 / 100 g and 1,438 g I2 / 100 g), compared to the results from the colorimetric technique, with values between 1,61 g I2 / 100 g and 3,30 g I2 / 100 g.

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    ABSTRACT: Biodiesel consists of long-chain fatty acid esters, derived from renewable sources such as vegetable oils, and its utilization is associated to the substitution of the diesel oil in engines. Depending on the raw material, biodiesel can contain more or less unsaturated fatty acids in its composition, which are susceptible to oxidation reactions accelerated by exposition to oxygen and high temperatures, being able to change into polymerized compounds. The objective of this work was to determine the oxidative stability of biodiesel produced by ethanolysis of neutralized, refined, soybean frying oil waste, and partially hydrogenated soybean frying oil waste. The evaluation was conducted by means of the Rancimat® equipment, at temperatures of 100 and 105ºC, with an air flow of 20 L h-1. The fatty acid composition was determined by GC and the iodine value was calculated. It was observed that even though the neutralized, refined and waste frying soybean oils presented close comparable iodine values, biodiesel presented different oxidative stabilities. The biodiesel from neutralized soybean oil presented greater stability, followed by the refined and the frying waste. Due to the natural antioxidants in its composition, the neutralized soybean oil promoted a larger oxidative stability of the produced biodiesel. During the deodorization process, the vegetable oils lose part of these antioxidants, therefore the biodiesel from refined soybean oil presented a reduced stability. The thermal process degrades the antioxidants, thus the biodiesel from frying waste oil resulted in lower stability, the same occuring with the biodiesel from partially hydrogenated waste oil, even though having lower iodine values than the other.
    Scientia Agricola 01/2005; · 0.80 Impact Factor

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