Biblioteca do Café
URI permanente desta seçãohttps://sbicafe.ufv.br/handle/123456789/1
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Item Investigation of the impact of natural antioxidants found in coffee leaves, yerba mate, and jambolan pulp on the induction period and rate constant of biodiesel oxidation reaction in the presence of metallic ions(Sociedade Brasileira de Química, 2025-01-27) Branco, Isadora G.; Campos, Julia W.; Sousa, Eduardo G. de; Silva, Nathan F.; Gonçales Filho, José; Pauli, Elis; Romagnoli, Érica S.; Mantovani, Ana C. G.; Borsato, DionisioThe present study describes the antioxidant potential of ethanolic extracts of yerba mate (Ilex paraguariensis), coffee leaves (Coffea arabica) and jambolan pulp (Syzygium cumini Lamarck) when added to biodiesel, with and without chromium (Cr3+), manganese (Mn2+) and cobalt (Co2+) metal ions, measuring the induction period (IP) and the rate constant (k) of the oxidation reaction at 110 °C. Antioxidant activity was observed in all extracts, as they reduced k and increased the IP compared to the control sample. The coffee leaves extract had the most pronounced positive effect, increasing the IP to 12.42 h and reducing k by 5.9 times. However, biodiesel containing metallic ions of chromium, manganese and cobalt, both with and without natural extracts, reduced the IP in all assays conducted in this study. The natural yerba mate extract was the most affected by the manganese ion (Mn2+), reducing the IP by 41.61%. The chromium ion (Cr3+) had the least impact on the biodiesel oxidation process in the presence of coffee leaves extract, increasing the rate constant by 3.55%. Furthermore, the alcoholic jambolan pulp extract was the one that presented the best antioxidant properties in the presence of metal ions.Item Oxidative stability of biodiesel in the presence of leaves and fruit extracts(Universidade Federal do Ceará, 2025-05-09) Branco, Isadora Guilherme; Romagnoli, Erica Signori; Gonçales Filho, José; Mantovani, Ana Carolina Gomes; Borsato, DionisioThis research evaluated the efficiency of ethanolic extracts from yerba mate leaves (Ilex paraguariensis), coffee leaves (coffea arabica), and jambolan pulp (Syzygium cumini Lamarck) through the application of the simplex-centroid mixture design, the super modified simplex optimization algorithm, and the functions of desirability, using the induction period (IP) and the rate constant (k) of the biodiesel oxidation reaction at 110 °C as responses. Antioxidant activity was observed in all extracts, manifesting either by reducing the rate constant or extending the biodiesel induction period in comparison to the control sample. The mathematical models derived from the simplex-centroid design exhibited adjusted determination coefficients of 0.990 for the IP model and 0.960 for the k model. Analysis of variance indicated the significance of both models at the 5% significance level for IP and k, with p1 = 7.382 × 10−4 and p2 = 1.177 × 10−3, respectively. The lack of fit was not significant at the same level with p1 = 0.132 and p2 = 0.653, showing that they can be used for predictive purposes. The analysis of the response surface and optimization using the super modified simplex method revealed that higher proportions of coffee leaves extract in the mixture yielded superior IP values and lower k values.