The influence of the reaction temperature
The transesterification reaction of WCO was performed at different durations ranging from 1 h to 6 h to study the effect of the reaction time on the FAME content. The other reaction parameters with BMK10 catalyst remained constant as follows: methanol: oil molar ratio of 12:1, 3.5 wt% catalyst loading, and 150 °C. Fig. 6 shows the effect of the reaction time. A sufficient reaction time was crucial to obtain a high FAME content in transesterification, because a rapid increase in FAME content was only observed after a certain time Calhex 231 required for the formation of a sufficient amount of these triglyceride derivatives. Therefore, the FAME content increased with time until a point where the changes in the FAME content were no longer significant. In the study of Karabas  on acorn kernel oil methyl ester, they confirmed that the reaction time has the strongest influence on production. Thus, an increase in the FAME content was observed from 1 h to 5 h, and the FAME content was unchanged after a reaction time of 5 h. A difference of only 0.52% in the FAME content was observed between the reaction times of 5 and 6 h. The FAME content was only 54.16% when the reaction time was only 1 h, and secondary xylem was considered quite low compared with the FAME content obtained from a longer reaction time. The transesterification reaction did not reach equilibrium within such a short time period. Mixing and dispersion between reactants might not be sufficient to produce a high FAME content. As the reaction time increased, more contact time between reactants and catalyst became available, which led to more frequent collision. The formation of FAME during the transesterification reaction was more favorable at such operating conditions. A slight decrease in the FAME content at 6 h might be due to reverse transesterification, in which FAME formation was no longer favorable. The increase in FAME yield with time was proven by Ngamcharussrivichai et al. , who reported a FAME yield of 27.2% at a reaction time of 2 h, and the highest yield of FAME (99.9%) from palm kernel oil using Ca(NO3)2-modified dolomite catalyst was 3 h at 10 wt% catalyst loading and methanol: oil molar ratio of 15:1.