Estudo da estabilidade oxidativa de amostras de biodiesel obtidas a partir de diferentes fontes de oleaginosas

• Ano de defesa: 2010
• Autor(a) principal: Machado, Yguatyara de Luna
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Engenharia química; Biodiesel; Antioxidantes; Indução
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/15878

Biodiesel is defined as a mixture of alkyl esters obtained by the transesterification reaction of triglycerides such as vegetable oil or animal fat with a short-chained alcohol, usually methanol or ethanol in presence of basic catalysts. However, biodiesel obtained from raw materials which have unsaturated fatty acids in their composition may show less oxidative stability. This fact may jeopardize its storage and use as fuel, but its low stability may be increased by the addition of additives. In this work, a kinetic study of the oxidation reaction of biodiesel samples from castor oil and soybean oil was carried out at different temperatures and pure oxygen pressure of 700 kPa. Kinetic studies were carried out at temperatures of 100, 120 and 140°C with preset stops, as well as the efficiencies of some synthetic antioxidant additives (BHA, PG, TBHQ, DBPC) were evaluated. This study was made according to method ASTM 7545. This method is consisted by submitting samples with and without additives to an oxidation test at 140°C and pure oxygen pressure of 700 kPa. The oxidation degree was monitored by Total Acid Number, Kinematic Viscosity at 40°C and Density at 20°C as parameters. The results showed that temperature increase has a significant effect on oxidation degree of the samples. The results also showed that synthetic antioxidants increased significantly the oxidative stability of the evaluated biodiesel samples. The antioxidant DBPC increased oxidative stability of biodiesel from castor oil by around 6 times. Samples with additive TBHQ showed similar behavior, but samples with higher concentration of DBPC (5000 ppm) showed smaller induction periods. BHA’s antioxidant maximum activity was obtained at concentration of 2000 ppm. The best performance of antioxidant PG was at concentration of 3000 ppm. Antioxidant TBHQ increased oxidative stability of biodiesel from soybean oil by 2 times, while PG showed best activity for the concentration of 1000 ppm and the same level of activity was reached for BHA for concentrations above 2000 ppm.