Storage stability and ageing effect of biodiesel blends treated with different antioxidants

This study investigates the impact of various synthetic phenolic antioxidants on the oxidation stability of biodiesel blends with the employment of the modified Rancimat method. The experimental results revealed that an improvement in oxidation stability could be achieved with all antioxidants tested. Butylated hydroxytoluene (BHT) and butylated hydroxyanisol (BHA) displayed the lowest effectiveness in neat biodiesel, whereas their use in biodiesel blends showed a greater stabilizing potential. Propyl gallate (PG) and pyrogallol (PA) additives showed the strongest effectiveness in both the neat biodiesel and the biodiesel blends. During a naturally ageing process of the biodiesel blends which was conducted for a period of 10 weeks, samples were taken every 2 weeks to measure the oxidation stability, kinematic viscosity and acid value. This process was designed in such manner to simulate the ageing of an automotive biofuel stored in the fuel tank of a vehicle. The results showed a sharp decrease in fuel stability over time. Although limited effects were observed in viscosity, the acid value was significantly increased over time. The addition of antioxidants resulted in some increases in viscosity and acid value of the biodiesel blends.