Abstract:
Biodiesel was prepared using base catalyzed methanolysis of sunflower oil. The oxidative stability of the neat biodiesel, as well as samples spiked with 0.15 wt% antioxidant was quantified by induction periods (IP) obtained with the Rancimat method according to the tangent method. The neat stabilizers, binary blends and a ternary mixture of poly(1,2-dihydro-2,2,4-trimethylquinoline) (Orox PK), tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane (Anox 20), and tris(nonylphenyl)phoshite (Naugard P) were tested. Of these, Anox 20 was the most effective stabilizer while Naugard P proved ineffective for the sunflower biodiesel. Synergistic improvement of oxidative stability was observed on partial substitution of this phenolic-based compound with the Orox PK. Combinations of the latter amine-based stabilizer with other phenolic antioxidants did not show any synergy, with perhaps the exception of DTBHQ. At a dosage of 0.15 wt%, only TBHQ, propyl gallate and pyrogallol, as well as their 2:1 blends with Orox PK, provided IP values that exceeded 8 h as required by the European Standard EN 14,214 for biodiesel.
