Optimization of the microwave-enhanced transesterification for coconut biodiesel production

• Main Author: Conejos, Joy Rochelle V.
• Format: text
• Language: English
• Published: Animo Repository 2011
• Subjects: Coconut oil as fuel; Transesterification; Biodiesel fuels; Renewable energy sources; Biomass energy; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/etd_masteral/6995
• Institution: De La Salle University

Extensive work has been done on the transesterification of non-edible and edible vegetable oils including coconut oil; however, no significant work has been done on the transesterification of coconut oil using microwave process intensification in order to accelerate the rate of reaction thereby increasing the efficiency of production. The microwave-enhanced process is expected to bring about considerable time saving as well as cost in production. Thus, an optimization study on biodiesel production from refined, bleached, and deodorized (RBD) coconut oil was conducted using alkali-catalyzed transesterification process via microwave-enhanced heating. The optimum conversion of the coco-biodiesel produced using two-level fraction factorial experimental design consisting of these test parameters, i.e., catalyst dosage (as OH-) per unit oil, methanol-to-oil mole ratio, reaction temperature, reaction time, type of catalyst (i.e., KOH and NaOH), and presence of agitation, were evaluated. Using the analysis of variance (ANOVA) at 5% level of significance, the significant parameters in conversion are the catalyst dosage (as OH-) per unit oil and presence of agitation. These parameters which proved to be significant in conversion within the experimental range investigated were further optimized using the central composite rotatable design. The optimum percent conversion is predicted to be at 94.48% using 0.44% catalyst dosage per unit oil and with the application of agitation (at ~120 rpm) in the process. The results were compared to the biodiesel produced via conventional heating. Based on comparison done within the experimental range conducted, conversion levels of coconut oil to methyl esters using conventional heating were in the range of 82.85 to 96.34% as compared to the levels of conversion achieved by employing microwave-enhanced transesterification which was in the range of 83.79 to 93.33%. Results showed that microwave process intensification results in drastic reductions in reaction time needed to achieve conversion levels that are comparable to those achieved via conventional processing. The results also showed that almost all of the most important properties of the biodiesel are very close and in range with those of the biodiesel specifications set by the Philippine National Standards and the internationally-accepted standards for biodiesel quality.