Thermal and oxidative stability of ethyl soybean biodiesel with cagaite (Eugenia dysenterica DC.) leaves extract as additive

This work aimed to evaluate the thermal and oxidative stability of samples of ethyl soybean biodiesel (BES) added with the ethanol extract of Eugenia dysenterica DC. leaves (EFC), popularly known in Brazil as cagaite. The BES samples were added with EFC in quantities of 500, 1000 and 2000 ppm. For comparison sake, a sample of BES was added with 2000 ppm TBHQ. All samples were stored at room temperature and protected from light for thirty days. Thermal stability was evaluated using thermogravimetry/derived thermogravimetry (TGA/DTG) in which the initial temperature and final decomposition temperature were measured, in Celsius degrees. Thermal stability was analyzed through the induction period, in hours (h), using the Rancimat (R) method. As the mass of EFC added in BES increased, there was an increase in the induction period of the stored samples, and the AB3 and AB4 samples showed induction periods longer than that stipulated by the ANP (8h) during the storage period. In addition, sample AB3 had the highest initial decomposition temperature, inferior only to the sample added with TBHQ (AB4). All the additives with EFC also showed an increase in decomposition temperatures and in the induction period and this shows the action of antioxidants present in the EFC in delaying the decomposition of BES, showing that it is an important additive to improve the quality of this biofuel.

Automated summary

This study aimed to evaluate the thermal and oxidative stability of ethyl soybean biodiesel (BES) samples added with Eugenia dysenterica DC. leaves extract (EFC), a plant known as cagaite in Brazil. The results showed that as the amount of EFC added to BES increased, the induction period of the stored samples also increased, exceeding the specified limit in some cases. Additionally, all the samples added with EFC exhibited increased decomposition temperatures and induction periods, indicating the role of EFC antioxidants in delaying the decomposition of BES and improving the quality of this biofuel.