Produção de biodiesel em reator de atomização

Abstract

Biodiesel is an alternative fuel widely used for partial or total replacement of fossil fuels. Although biodiesel production is undoubtedly a mature technology, there are still ways to improve it, especially through the process intensification. So, the present study investigated the esterification of oleic acid with ethanol and the transesterification of sunflower oil with ethanol for biodiesel production in a non-conventional atomization reactor. The effects of the oleic acid and sunflower oil flow rates, atomization pressure, temperature and catalyst concentration were evaluated. A mathematical model was also developed to describe the conversion of oleic acid to ethyl ester as a function of molar concentration of components and operating conditions of the reactor. A hybrid estimation of parameters (activation energy, pre-exponential factor, equilibrium constants, and solubility) was performed. In the esterification, the Pareto analysis has shown that the increase of temperature in the reactor and the increase of atomization pressure have improved the conversion of oleic acid. Higher pressure values in the atomization vessel led to the generation of small oleic acid and sunflower oil droplets, which accelerated reagent consumption during the reaction. On the other hand, conversion values are reduced by increasing oleic acid flow rate. In the transesterification, it was observed that the flow rate had a negative effect and, the pressure had a positive effect on the conversion of sunflower oil. Droplet size distribution analysis showed that increasing pressure in the atomization chamber led to a reduction in droplet size, which explains the effects on ethyl ester conversion. The highest conversion of oleic acid was obtained under the following reaction conditions: 70 ◦C, 1.5 bar, oleic acid flow rate equal to 1.3 g/min using 0.6% catalyst, and 2 h of reaction time. In the transesterification, conversions of 98.3% were obtained with a flow rate of 3 g/min of sunflower oil at 50 ◦C, 1.5 bar and 1.0% of catalyst in 1 h. The mathematical model achieved good fit with independent experimental data and the parameters obtained from the hybrid estimation strategy were in accordance with the literature.