PRODUÇÃO DE ANTIOXIDANTE PARA O BIODIESEL A PARTIR DA CASCA DE SEMENTE DE HB

Abstract

Research into biofuels as alternatives to fossil fuels has been expanding on the global energy scene, as they present environmental and economic advantages. Among biofuels, biodiesel is a viable alternative to petroleum diesel, since its use contributes to reducing the emission of greenhouse gas pollutants, in addition to being biodegradable and presenting commercial and economic advantages. However, biodiesel, as it is obtained from oils and fats that have unsaturated fatty acids in their composition, has low oxidation stability, which causes financial losses in the transport, storage and consumption stages of this biofuel. Therefore, it is mandatory to add antioxidants to biodiesel, aiming to increase its oxidation stability. The HB seed shell is a co-product of a raw material widely produced and sold in Brazil, but which does not yet have a profitable destination. Therefore, the objective of this work was to produce acidic, basic and neutral extracts from HB seed shells to be used as antioxidant additives to soybean biodiesel. To analyze the antioxidant activity of the extracts, the DPPH (2,2-diphenyl-1- picrylhydrazyl) free radical capture test was used. Furthermore, in the work the quantification of phenolic compounds was carried out in the extracts using the Folin Ciocalteau method, and their identification by liquid chromatography (UHPLC). The extracts were added to biodiesel in the biodiesel production or washing stages, by two different methods, mechanical agitation and ultrasound. To analyze the oxidation stability of control biodiesel and biodiesel with the addition of antioxidant extracts, the Rancimat 873 device was used to obtain and compare their induction time (IT). Based on the results, the acid extract produced with HB seed shell in its optimized conditions of 60 min extraction time and 106 g.L-1 concentration and incorporated by mechanical agitation was able to increase the induction time of soy biodiesel when used in combination with 100 ppm TBHQ from 3.65 + 0.12 hours (control biodiesel without added antioxidants) to 16.29 + 0.14 hours. This same extract reached 79.664% antioxidant activity by the DPPH free radical capture test, 761.15 + 116.23 mg EAG.100g-1 of phenolic compounds, with ellagic acid and caffeic acid as the main compounds found in the extract. Furthermore, soybean biodiesel plus acid extract in the washing stage by mechanical agitation presented physicochemical characterization results in accordance with ANP reference values, with the visual appearance of a transparent biodiesel free of impurities, with 882 + 0.2 kg.m³ specific mass at 20 °C, 123 + 1.0 °C flash point, and conductivity of 341 + 10.0 pS/m. Therefore, it is considered that the acid extract produced with HB seed hulls is viable for increasing the oxidation stability of soybean biodiesel.