Determination of the Kinetics and Thermodynamics Parameters of Biodiesel Oxidation Reaction Obtained from an Optimized Mixture of Vegetable Oil and Animal Fat

The temperature influence on the oxidation stability of biodiesel from ternary mixture of vegetable oil and animal fat (50% of soybean oil, 20% of beef tallow, and 30% of poultry fat) was evaluated at temperatures ranging from 110 to 130 °C applying the Arrhenius and Eyring equations. The kinetics and thermodynamics parameters determined, considering first-order reaction rate kinetics, were rate constant ( k ), varying from 0.5479 to 1.7110 h –1, activation energy ( E a ) of 72.01 kJ mol –1, pre-exponential factor ( A ) of 3.84 × 10 9 h –1, enthalpy of activation (Δ H ‡ ) of 68.75 kJ mol –1, entropy of activation (Δ S ‡ ) of −72.05 J K –1 mol –1, and Gibb’s free energy of activation (Δ G ‡ ) average of 97.08 kJ mol –1 . Based on the activation complex theory (ACT), the thermodynamic activation parameters indicated a nonspontaneous, endergonic, and endothermic process: Δ G ‡ > 0, Δ H ‡ > 0, and Δ S ‡ < 0, with estimated storage time of 149.82 d at 25 °C.