Multiple response optimization of vegetable oils fatty acid composition to improve biodiesel physical properties

► Prediction models of five biodiesel properties have been proposed. ► There is a lineal trend for LCV, CN and CFPP models. ► μ and FP models follow a quadratic tendency. ► A combination of LC and UD to simultaneously optimize fuel properties has been found. ► A reduction of LC increases UD, keeping biodiesel under European standard limits. The effect of fatty acids chain length (LC) and its interaction with unsaturation degree (UD) on important biodiesel quality parameters was studied. Low calorific value, kinematic viscosity, flash point, cetane number and cold filter plugging point of biodiesel blends covering a wide range of fatty acids were analyzed. Analytical results were processed with statistical regression to obtain a prediction model for each property, combining LC and UD. Due to the antagonistic effects of the chemical composition over quality properties, the Derringer desirability function was proposed to allow the most suitable fatty acid composition. This target was achieved considering an average of 1.26 double bounds and 17 carbon atoms. A set of combinations of LC and UD values that provides a biodiesel that fits the European standard EN 14214 was proposed. It was found that a reduction of FAME LC allows a lower UD while keeping biodiesel specifications under the standard limits.