Kelly Roberta Spacino

Study of oxidation kinetics of b100 biodiesel from soybean and pig fat: activation energy determination.

The quality of biodiesel is extremely important for its commercialization and use; oxidation of biodiesel is a critical factor because it decreases the fuel storage time. A commercial biodiesel was mixed with synthetic antioxidants, according to a simplex-centroid experimental mixture design, and its stability was evaluated through induction period and activation energy. In all trials, addition of antioxidants increased activation energy in the mixtures containing tertiary butylhydroquinone (TBHQ). When a mixture containing 50% TBHQ and 50% butylated hydroxyanisole was used, synergistic effect was observed, and the major activation energy obtained was 104.43 kJ mol-1.

Aplicação do delineamento simplex-centroide no estudo da cinética da oxidação de biodiesel B100 em mistura com antioxidantes sintéticos

Antioxidants are an alternative to prevent or slow the degradation of the biofuel. In this study, it was evaluated the oxidative stability of B100 biodiesel from soybean oil in the presence of three commercial synthetic antioxidants, butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), pure or blended, from the experimental design of simplex-centroid mixture. The reaction order and rate constant were also calculated for all tests. The treatment containing pure TBHQ proved to be the most effective, proven by design, the optimum mix obtained and the rate constant. Binary and ternary mixtures containing TBHQ also showed appreciable antioxidant effect.

Apparent activation energy and relative protection factor of natural antioxidants in mixture with biodiesel

ABSTRACT In Brazil, biodiesel mainly consists of unsaturated fatty acid esters, which gives low oxidative stability. Therefore, natural antioxidants present themselves as an alternative to prevent oxidative deterioration due to the presence of phenolic compounds in their structure, capable of inhibiting free radicals by donating hydrogen atoms. Extracts of pepper, bacupari leaves, coffee leaves and sage were added to biodiesel B100 to verify the efficiency of antioxidant on the oxidation reaction of biodiesel, using as a parameter the comparative relative protection factor (RPF). Linearity deviations were observed in the graph of the logarithm of the rate constant as a function of the inverse of temperature, indicating that the activation energy varies at the different temperatures 110, 115, 120 and 125°C of the accelerated Rancimat test. The RPF analyzed by the simplex-centroid design proved to be a suitable parameter to verify the efficiency of natural antioxidants in the protection of the oxidation reaction, indicating an optimized mixture of 25% pepper, 60% coffee leaves and 15% sage.