Produção de biodiesel por transesterificação em banho ultrassônico utilizando biodiesel como cossolvente

Abstract

Biodiesel is a renewable fuel that can be used as an alternative to other non-renewable fuels. The simplest process used to produce this biofuel is transesterification, which is a reaction between an oil and an alcohol in the presence of a catalyst. Due to the difficulty of miscibility of the reagents in the reaction, the use of methods that employ agitation and heating are necessary during the transesterification process. Among the various methods available ultrasound is an alternative technology that is able to improve the miscibility of the reagents, accelerate the reaction, and increase the conversion. In order to further facilitate the homogenization of the reaction and thereby obtaining biodiesel, a cosolvent can be used. In light of this, as presented in the current study, biodiesel was synthesized by means of transesterification in an ultrasonic bath with and without the use of biodiesel as a cosolvent. Ethanol and soybean oil were used as reagents in conjunction with potassium hydroxide as the catalyst. The biodiesels were produced at variable reaction times (15, 30, 60, 90 and 120 minutes). All samples were evaluated for conversion and acid value, and samples with cosolvent were also evaluated for aspect and density. The best conversion values at all reaction times were obtained using cosolvent. The highest conversion was 78% obtained at 60 minutes of reaction with the cosolvent. The samples of biodiesel without cosolvent had an acid value at the level as specified by law, while the samples produced with cosolvent at 15 and 60 minutes had a value in excess of the limit. The biodiesels with cosolvent resulted in a cloudy appearance at 15 and 30 minutes of reaction time whilst the other samples were transparent. The density values were around 871 Kg/m3 for all samples in accordance to the standard. Thus, it can therefore be concluded that the presence of the cosolvent combined with the energy produced by the ultrasound improves the miscibility of the reagents and increase the conversion of the transesterification reaction.