Study of kinetics and thermodynamic parameters of the degradation process of biodiesel produced from fish viscera oil

•Biodiesel production from oil viscera of Nile tilapia•Kinetic study showed that biodiesel degradation process has a low activation energy.•Thermodynamic parameters showed that the biodiesel degradation process is not spontaneous (ΔG≠ > 0) and endothermic (∆ H≠ < 0).

The present study determines the kinetic and thermodynamic parameters of the degradation process of the biodiesel produced from fish viscera oil. The analyses were performed through the accelerated trials of oxidation of biodiesel (EN 14112) at different temperatures (100, 105, 110, 115, 120 e 125 °C). Through the analyses of the results of the induction period, the reaction was considered to be of the first order. It was determined by the rate constants (K) varying from 0.0868 to 0.42271 h− 1, activation energy (Ea) of 81.99 kJ·mol− 1, the pre-exponential factor (A) of 2.61 × 1010 h− 1, enthalpy of activation (ΔH≠) of 78.79 kJ·mol− 1, entropy of activation (ΔS≠) - 55.94 J·k− 1·mol− 1 and Gibb's free energy of activation (ΔG≠) average of 100.25 kJ·mol− 1. The results showed that biodiesel oxidation reaction is non-spontaneous (ΔG≠ > 0), endothermic (ΔH≠ > 0), and that the temperature and the oxidation concentration influences significantly the degradation process of methyl esters.

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