Avaliação da atividade antioxidante dos ácidos caféico e ferúlico no controle da estabilidade oxidativa do biodiesel de soja.

• Autor(a) principal: Damasceno, Sarah Soares
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/tede/7069
• topic: Biodiesel de soja; Estabilidade oxidativa; Antioxidantes; Técnicas aceleradas; Cromatografia; Biodiesel from soybeans; Oxidative stability; Antioxidants; Accelerated techniques; Chromatography; CIENCIAS EXATAS E DA TERRA::QUIMICA

The lipid oxidation is a critic factor in the biodiesel quality loss, in particular of soy biodiesel, because its esters composition favors the development of the oxidative degradation, due to the amount of the unsaturated fatty acid esters such as, oleate, linoleate and ethyl linolenate. In this work, accelerated techniques (rancimat, petroOXY and thermal analysis) high performance liquid chromatography (HPLC) was done in order to determine the oxidative stability of biodiesel from soybean (BSJ) and from the additive biodiesel with antioxidants, caffeic acid (BSC), ferulic acid (BSF) and tert-butylhydroquinone (BST) during the storage period. In determining the induction period (PI) by the rancimat method the three antioxidants were effective in delaying the oxidation process at the initial time of storage. Different from the BSF and BST samples, the BSC sample kept its PI value during the storage period above the value required by the EN 14112 standard. The oxidative stability assayed by the petroOXY method showed the same convergence in its results, ie, the caffeic acid was the most efficient antioxidant throughout the storage period. In comparison to the rancimat and petroOXY method, the technique of pressurized differential scanning calorimetry (P-DSC) showed the same susceptibility to oxidation for the evaluated samples. This method proved to be useful to apply in the oxidative stability of biodiesel evaluation with antioxidants, requiring less quantity of samples and less analysis time. In evaluating the thermal resistance of antioxidants was observed by thermogravimetry a lower decomposition temperature for the tert-butylhydroquinone compared to other antioxidants, confirmed this fact with the values of oxidation induction time and induction period obtained by the techniques accelerated. Monitoring the concentration of unsaturated esters by HPLC during storage showed a greater reduction in the concentration of ethyl oleate and linolenato BSJ for the sample. The action of antioxidants was evidenced by a smaller reduction in the concentration of esters for samples of BSC, BST and BSF. The oxidative stability of biodiesel samples evaluated by Rancimat, petroOXY, P-DSC showed the following trend: BSC > BSF > BST. Since the order of HPLC greater resistance to oxidation: BSC > BST > BSF. According to the results obtained showed that the antioxidant activity is correlated to its molecular structure and thermal stability.