Stabilization of diesel–biodiesel–ethanol (DBE) blends: formulation of an additive from renewable sources

Sustainable policies led to partially replace fossil diesel fuel by biodiesel. However, other technologies, such as diesel–biodiesel–ethanol (DBE) blends, are being investigated. The major challenge related to these mixtures is the improvement in the miscibility and the stability of alcohol in diesel fuel. The stabilization effect of ternary additives, composed of biodiesel and vegetal oil from two renewable sources (soybean and castor oil) and n -butanol obtained through Doehlert designs of experiments, was assessed. This article initially investigated blends with commercial Brazilian diesel S10 fuel with 7 vol% of biodiesel, B7, and hydrous ethanol. However, adequacy to potential future fuels was investigated for Brazilian diesel S10 fuel with up to 30 vol% of biodiesel and anhydrous ethanol. The best additive was defined as a mixture of 72.5 vol% of castor oil, 17.5 vol% of soybean biodiesel and 10 vol% of n -butanol in diesel B15 fuel. Diversity on the carbon chain length and moieties in the additive was required to improve the miscibility of ethanol in diesel fuel. Nevertheless, high content of n -butanol did not contribute to stabilization since it acted as an extraction solvent. The results also showed that a minimum addition of 1.0 vol% was required to have a sufficient short-term and long-term stability in diesel B15 blends at temperatures higher than 10 °C and anhydrous ethanol content up to 20 vol%. Using such blends, the displacement of fossil fuel demand by biofuels can be increased from 7 to 33 vol%.