Avaliação das concentrações dos ácidos e ésteres graxos na produção de biodiesel de óleo de soja por transesterificação alcalina

Abstract

Biodiesel, a biofuel alternative to petroleum diesel, consists of a mixture of monoalkyl esters of fatty acids. The most common method of obtaining biodiesel is through the reaction of alkaline transesterification of oleaginous or animal fat with alcohols of short chains, such as methanol and ethanol. Transesterification for biodiesel production is a process involving mass transfer and chemical reaction effects. In this sense, alcohols (methanol or ethanol) and refined soybean oil were mixed in the alcohol: oil: 6: 1 molar ratio and stirred at 60 ° C with a stirrer speed of 600 rpm in order to analyze the mass transfer of the individual fatty acids from soybean oil to alcohol phase. Samples of the alcohol phase were collected at determined times, then they were transesterified using an analytical method and analyzed by gas chromatography. In the reactive process, biodiesel was produce from refined soybean oil, using the alcohols methanol and ethanol. The experiments were run under the conditions specified above, using sodium hydroxide as the catalyst at the concentration of 0.5% (w / w) relative to the oil. The evolution of alkyl esters concentrations (biodiesel) over time were obtain by gas chromatographic analysis. Comparative analysis was made of the temporal evolution and yields of the individual fatty esters. The analysis of the results showed that the fatty acids in higher concentrations in the raw material (C16:0; C18:1; C18:2) reached higher levels of mass transfer in the alcohol phase (ethanol, methanol). It was observe in the reactive systems that the esters of palmitic and linoleic acids were favored in the process, whereas those of oleic acids presented lower reactivity.