Optimization of Biodiesel Production from Iranian Bitter Almond Oil Using Statistical Approach

Response surface methodology (RSM) was applied to optimize the process of biodiesel production from Iranian bitter almond oil. Design of experiments was performed by application of a 5-level-3-factor central composite design in order to study the effect of different factors on the product yield, biodiesel yield and biodiesel purity. These factors were reaction temperature (30–70 °C), catalyst concentration (0.3–1.7 % w/w) and methanol to oil molar ratio (4.4–13.6 mol/mol). A quadratic model was suggested for the prediction of the biodiesel yield. Analysis of variance revealed that the factors were significant on the production process of biodiesel. For each factor, the optimum value was determined as: reaction temperature of 35 °C, catalyst (NaOH) concentration of 1.4 wt% and methanol to oil molar ratio of 9.7 mol/mol. At the optimal condition, the actual values of the product yield, biodiesel yield and biodiesel purity were 96.7, 94.7 and 97.9 wt%, respectively. At these conditions, the predicted values of the product yield, biodiesel yield and biodiesel purity were 98.1, 96.3 and 98.2 wt%, respectively. The fuel properties of the biodiesel were measured and compared with those of petroleum diesel, ASTM 6751 and EN 14214 biodiesel standards and a reasonable compatibility was observed.