Avaliação da conversão do óleo de soja em biodiesel utilizando álcoois de cadeia curta

Abstract

Biodiesel is one of the alternatives in reducing environmental impacts as it is a fuel derived from renewable raw materials such as vegetable oils and animal fats. It can be obtained through the transesterification reaction between an alcohol and triglycerides in the presence or not of a catalyst, having as product an ester, which is biodiesel, and glycerin. The objective of this work was the evaluation of the use of short chain alcohols in the transesterification reaction of soybean oil, using a homogeneous base catalyst (potassium hydroxide), obtaining as a result the model for the conversion of the reaction and the reaction kinetics for the biodiesel made with butanol. The transesterification reactions were carried out in a jacketed glass reactor, with a coupled condenser and a heating bath. Initially, for the conversion study, reactions were carried out with different alcohols, varying the alcohol: oil to biodiesel molar ratio using methanol, ethanol, 2-propanol and butanol as alcohols, then to evaluate the other properties, a factorial design was carried out with butanol in the reaction and with the following conditions: alcohol: oil ratio of 4: 1 to 8: 1, 1 to 2%, 1 to 2 hours and 65 ° C. To obtain the kinetic model, samples were selected between times t0 and tf (60 minutes). For all samples, density and viscosity were analyzed and their conversions were measured using thermogravimetric analysis. In the density analysis, of the samples obtained by the factorial design, it varied between 889.41 kg/m3 and 850.18 kg/m3, whereas for the viscosity it varied between 11.10 cSt and 3.10 cSt. When increasing the conversion to ester, the density and viscosity decreased in their values. For the conversion analysis, the four types of alcohol with a 10:1 molar ratio were found: methanol 99.28%, ethanol 81.72%, 2-propanol 7.50% and butanol 49.74%. For planning with butanol, the optimum point occurred with an 8: 1 ratio, 2% by mass of catalyst, for two hours, where it obtained 76.24% conversion. With the model obtained by factorial design 23, it was found that the three factors analyzed were significant, with an average error between the predicted and experimental values of 2.3%. The reaction was shown to be of second order with a kinetic constant of 3x10-5 min-1. Thus, it can be concludedthat when comparing alcohols, methanol obtained better yield and the biodiesel produced with butanol obtained conversion values consistent with the works found in the literature making this alcohol an alternative in the production of biofuel from sources renewable and better fuel lubricity.