Characterization of Biodiesel Produced from the Transesterification of RPO (Refined Palm Oil) and Recycled Methanol Using an NaOH Catalyst

The transesterification reaction used in biodiesel production is reversible; thus, several approaches are required to achieve a high product yield. The use of excess methanol as a reactant is one method to shift the reaction equilibrium toward the product side. Unreacted methanol can be reused in subsequent transesterification reactions, helping to reduce material consumption. The objective of this study is to determine the optimum conditions for the transesterification reaction using recycled methanol and varying reaction times. The research consists of three stages: recycled methanol preparation, transesterification using recycled methanol, and product characterization. The preparation stage involves conducting a transesterification reaction of RPO to obtain recycled methanol. This is followed by the second stage, namely the transesterification reaction using recycled methanol. The transesterification of palm oil is carried out at a reaction temperature of 65 °C with an oil-to-methanol molar ratio of 1:6, 1% NaOH catalyst, stirring speed of 150 rpm, reaction times of 15, 30, 45, 60, and 75 minutes, and recycled methanol concentrations of 5%, 10%, and 15% of the fresh methanol feed mass. The reaction mixture is then neutralized and placed in a separation funnel. The upper layer, consisting of methyl ester, is subjected to characterization. The characterization includes density measurement, acid value determination, and methyl ester concentration analysis using GC. The optimum conditions are obtained in the transesterification of palm oil with the addition of 5% recycled methanol for 60 minutes, producing methyl ester with a density of 0.85 g/mL, an acid value of 0.42 mg KOH/g, and a concentration of 97.69%, meeting the SNI 7182:2015 standard. The results of this study are expected to provide useful information for future biodiesel research and for the biodiesel industry, indicating that the use of 5% recycled methanol can produce biodiesel that meets the required standards.