Antioxidants for biodiesel: Additives prepared from extracted fractions of bio-oil

•Lignocellulosic bio-oil as an antioxidant additive for biodiesel•Acetate esters improved extraction and solubility of bio-oil compounds in biodiesel•Less than 4 wt.% of bio-oil in biodiesel increased oxidation stability up to 475%•Good antioxidant performance of the additives over time

Unlike petroleum diesel, the chemical structure of biodiesel makes it prone to oxidation during long-term storage, thus involving fuel quality deterioration. Therefore, the addition of antioxidants is usually required to meet the quality standards for biodiesel commercialization. Synthetic sterically-hindered phenols have been usually employed for this purpose as free radical scavenging antioxidants. However, naturally occurring phenolics are also available, for example, in the bio-oil produced in the pyrolysis of lignocellulosic biomass. In this work, the antioxidant potential of extracted fractions of lignocellulosic bio-oil has been evaluated. Different organic solvents were tested as extraction agents, acetate esters being the best ones for incorporating bio-oil antioxidant compounds into biodiesel. In the best case, the incorporation of a small concentration of bio-oil compounds (< 4 wt.%) led to an improvement of the biodiesel oxidation stability of 475% which, in our case, was enough to meet the European standard requirement.