Abstract:
Biodiesel has been recognized as a ‘‘green fuel’’, being the most attractive substitute to the conventional
petro-diesel. The unsaturated fatty acids present in biodiesel are susceptible to oxidation. One of the
main criteria used for the quality assessment of biodiesel is ‘storage oxidation stability’. Oxidation of
the esters during the long-term storage can lead to problems for the utilization of biodiesel in the engine
directly. Therefore, the addition of additives is required to protect the oxidation of biodiesel. This study
investigates the effect of antioxidant additives on oxidation stability of neat biodiesel [Karanja oil methyl
ester (KOME)] and its diesel blends. KOME was prepared by methanolic KOH catalyzed transesterification
of Karanja oil, which was produced from a non-edible oil feedstock from Indian sub-continent. Various
diesel–biodiesel blends (B5, B10, B15, B20, B25 and B40) were prepared with conventional diesels sold
at retail outlets of Northern India. Butylated hydroxy anisole (BHA), Butylated hydroxy toluene (BHT),
tert-Butylhydroxyquinone (TBHQ), Propyl-gallate (PrG) and Pyrogallol (PY) antioxidant additives were
selected for this study. Significant improvement in oxidation stability as well as in density and kinematic
viscosity of diesel–biodiesel blends was observed with all antioxidants studied. PY, PrG and BHA were
found most effective among all antioxidants tested, and their use in diesel/biodiesel blends showed a
greater stabilizing potential. All the samples were stored at room temperature in air-tight bottles under
ambient conditions. The aim of this study is to find the minimum required concentration of most effective
antioxidant to meet the storage oxidation stability specifications.
