Kinetic and thermodynamic assessment of the oxidation of diesel fuels containing HVO and biodiesel

Diesel fuel formulations containing hydrotreated vegetable oil (HVO) and biodiesel (content given after “B”), B10, B10R5 (5% HVO), B15, and B20, were aged at 43 °C for 15 weeks and 80 °C for seven days to evaluate their degradation process. Rancimat and PetroOxy induction periods (IPs) and the hydroperoxide number were monitored during aging, and the oxidation rates were determined considering a first-order kinetic model. Biodiesel contributed to stability decreasing once oxidation stability was reduced from B10 to B15 and to B20, and the hydroperoxide number was raised. B10 and B10R5 formulations showed similar degradation patterns, with better oxidation stability than B15 fuels, indicating that the HVO addition did not ease degradation. Blends of Bio 2 achieved a higher IP than blends of Bio 3, which showed a higher IP than blends of Bio 1, according to the oxidation tendency of Bios 1, 2, and 3. Formulations with Bio 2 showed lower oxidation rates (0.012–0.026 week − 1 ), indicating higher oxidation stability. Rates for B10 blends were close to those for B10R5 fuels, confirming no side effects of HVO. Activation energy (E a ), ranging from 93.2 to 115.6 kJ/mol, was determined using the Arrhenius equation. Higher E a for biodiesel led to higher values for B15 blends rather than B10R5 ones. Activation enthalpy (90.4 to 112.8 kJ/mol), entropy (-6.4 to 63.6 J/(K*mol)) and Gibbs free energy (91.5 to 93.8 kJ/mol) and the kinetic parameters compared the performance of the fuels, confirming the viability of HVO in the diesel fuel matrix over time.