Ultrasonic Irradiation Assisted Synthesis of Biodiesel from Crude Palm Oil Using Response Surface Methodology

Abstract

Crude palm oil (CPO) has been considered as a potential feedstock for biodiesel production in several tropical countries. Production of biodiesel from crude palm oil with 6 wt% of free fatty acid (FFA) using a low-frequency ultrasonic irradiation (40 kHz) technique was investigated in the present work. The objective of this study was to determine the relationship between various important parameters of the alkaline catalyzed transesterification process to obtain a high conversion to biodiesel. Response surface methodology (RSM) was used to statistically analyze and to optimize the operating parameters of that process. A central composite design (CCD) was adopted to study the effects of the methanol to oil molar ratio, the catalyst concentration, reaction temperature, and irradiation time on the conversion to biodiesel. The result from the RSM analysis indicated that the methanol to oil molar ratio, catalyst concentration and irradiation time had the most significant effects on the conversion to biodiesel. Moreover, a coefficient of determination (R2) value of 0.93 shows the fitness of a second-order model for the present study. Based on this second order model, the optimum conditions for alkaline catalyzed transesterification of CPO were found to be a methanol to oil molar ratio of 6.44:1, catalyst concentration of 1.25 wt%, reaction temperature of 38.44 °C and irradiation time of 25.96 minutes. At the calculated optimum condition, the conversion to biodiesel reached to 97.85%. Under these same conditions, the experimental value was 98.02±0.6%. The developed mathematical model has been proven to adequately describe the range of the experimental parameters studied and to provide a statistically accurate prediction of the optimum conversion to biodiesel.