(186d) Biodiesel Oxidative Stability Study: Factors and Improvement

Biodiesel, which is produced from animal and plant based-feedstocks, is more prone to oxidation than petroleum diesel. Fatty acid profile and natural antioxidant content are two of the inherent factors that affect the stability. Likewise, external factors such as exposure to air, heat, light and metals can initiate the onset of autoxidation and the subsequent degradation of fuel properties such as the kinematic viscosity and total acid number. This study examines the influence of the biodiesel composition, especially the minor components on the oxidative stability of biodiesel. Additionally, binary combinations of butylated hydroxyanisol (BHA), propyllgallate (PG), pyrogallol (PY) and t-butyl hydroxyquinone (TBHQ) were evaluated for their effect on oxidative stability under indoor and outdoor storage conditions as a function of time. Finally, the catalytic effect of metallic contaminants (Al, Cu, Fe and Zn) on biodiesel oxidation and possible antioxidant deactivation by the metals was investigated.

Results of this study provide a better understanding why biodiesel from different feedstocks has different degrees of oxidative stability and different responses to antioxidants. Additionally, permissible levels of metallic contaminants, with and without the presence of antioxidants, are described.