The Optimization of Bio-diesel Production from Waste Frying Oil Using Response Surface Methodology and the Investigation of Correlations for Changes in Basic Properties of Bio-petro-diesel Blends

Bio-diesel is derived from renewable sources and is steadily gaining attention and significance for use as an alternative or in blends with petro-diesel. In this study, bio-diesel was produced by alkaline-catalyzed transesterification process of waste frying oil at 60°C and 300 rpm. Response surface methodology, based on a central composite design, was employed to statistically evaluate and optimize the conditions for maximum conversion to bio-diesel and to study the significance and interaction of methanol to oil molar ratio, catalyst concentration, and reaction time on bio-diesel yield. A quadratic model equation was obtained for bio-diesel conversion by multiple regression analysis and the validity of the predicted model was confirmed. The optimum combinations for transesterification were determined to be methanol to oil, 9:1; catalyst amount, 0.6%; and reaction time, 1 h. The optimum and actual bio-diesel yields were 99.13 and 98.90%, respectively. The fuel properties of the produced bio-diesel and bio-petro-diesel blends were measured and compared with those of petro-diesel and the American Society for Testing and Materials standards for bio-diesel and bio-petro-diesel blends, and acceptable agreement was observed. Correlations were also established to describe the changes of basic properties of the produced fuel with the volumetric percentage of the bio-diesel for the bio-petro-diesel blends. © 2014 Copyright Taylor and Francis Group, LLC.