The present study was performed to optimize a heterogeneous calcium methoxide (Ca(OCH 3 ) 2 ) catalyzed transesterification process assisted with tetrahydrofuran (THF) as a cosolvent for biodiesel production from waste cooking oil. Response surface methodology (RSM) with a 5-level-4-factor central composite design was applied to investigate the effect of experimental factors on the percentage of fatty acid methyl ester (FAME) conversion. A quadratic model with an analysis of variance obtained from the RSM is suggested for the prediction of FAME conversion and reveals that 99.43% of the observed variation is explained by the model. The optimum conditions obtained from the RSM were 2.83 wt% of catalyst concentration, 11.6 : 1 methanol-to-oil molar ratio, 100.14 min of reaction time, and 8.65% v/v of THF in methanol concentration. Under these conditions, the properties of the produced biodiesel satisfied the standard requirement. THF as cosolvent successfully decreased the catalyst concentration, methanol-to-oil molar ratio, and reaction time when compared with biodiesel production without cosolvent. The results are encouraging for the application of Ca(OCH 3 ) 2 assisted with THF as a cosolvent for environmentally friendly and sustainable biodiesel production.

In this study, the biodiesel production of waste cooking oil using calcium methoxide as solid base catalyst was investigated. The calcium methoxide catalyst was synthesized from calcined quick lime reacted with methanol. The XRD result showed that the catalyst was successfully synthesized with sufficient purity. The strength of catalyst was examined on the transesterification reaction of waste cooking oil and methanol. Parameters affecting on transesterification such as the catalyst concentration, methanol-to-oil-molar ratio, reaction time and reaction temperature were investigated. The results showed that the percentage of fatty acid methyl ester conversion of 99.06%. The optimum conditions were achieved within 3 h using 3wt% catalyst concentration, 12:1 methanol-to-oil molar ratio and 65°C reaction temperature. In addition, the kinetic study of transesterification reaction was carried out at the temperature from 30°C to 65°C. The pseudo-first order was good agreement with the experiment results. The reaction rate constant (k) and activated energy (Ea) were determined as 0.023 min-1 and 55.77 kJ/mol, respectively.