# Synthesis of Biodiesel by Interestricification of Triglycerides with Methyl Formate
## 2 Intereesterification of Triglycerides with Methyl Formate
### Influence of Catalyst on the Product Yield  
The rate of triglyceride transesterification process is increased using homogeneous and heterogeneous catalysts, which can be alkaline and acidic, depending on the quality of the oil. The most commonly used homogeneous catalysts are sodium and potassium hydroxides and methoxides [4; 37; 44; 45]. If a higher acidity oil is used for the synthesis of biodiesel, acid catalysts (sulfuric, sulfidic, and chloric acids) are used as homogeneous catalysts [46; 47; 48]. Heterogeneous catalysts are both basic [49] and acidic [50], with the advantage of multiple uses [51]. Metal oxides [52], silicates [53], ion exchange resins [54], zeolites [55], and natural rocks [56] are used as heterogeneous catalysts, raw materials, or wastes containing calcium and magnesium (eggshells, crab, mussels, and snail shells) [57; 58; 59]. Biocatalysts are also used for oil transesterification [60; 61]. Similar to the transesterification process, the process of intereesterification is catalytic, and catalysts are used to increase its rate. Only a few studies have been performed on the intereesterification of oil using methyl formate, most of which were performed using chemical homogeneous catalysts. [PERSON] et al. used 28.6% sodium monoxide in methanol. A FAME content of 74.2% was obtained using 0.12% of catalyst (molar ratio of methyl formate-to-oil of 18:1, temperature 27 \({}^{\circ}\)C, and duration 60 min) [37]. [PERSON] et al. [41] \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Catalyst** & \begin{tabular}{c} **Molar Ratio of** \\ **Mehyl** \\ **Formate-To-Oil** \\ \end{tabular} & \begin{tabular}{c} **Ammount of** \\ **Catalyst** \\ \end{tabular} & \begin{tabular}{c} **Temperature,** \\ **’C** \\ \end{tabular} & \begin{tabular}{c} **Duration,** \\ **min** \\ \end{tabular} & \begin{tabular}{c} **Ester Content,** \\ **w\%** \\ \end{tabular} & \
\begin{tabular}{c} **Ester Yield, \%** \\ \end{tabular} &
\begin{tabular}{c} **Reference** \\ **Reference** \\ \end{tabular} \\ \hline
28.6\% sodium methoxide in methanol & 18:1 & 0.12 w\% & 27 & 60 & 74.2 & 88.3 & [37] \\ \hline potassium tert-butoxide & 18:1 &
\begin{tabular}{c} catalyst-to-oil \\ molar ratio of 0.08 \\ \end{tabular} & 25 & 60 & 71 & 71 & [41] \\ \hline
1 M potassium tert-butoxide in tetrahydrofuran & 18:1 (cosolvent tetrahydrofuran) & \begin{tabular}{c} catalyst-to-oil \\ molar ratio of 0.08 \\ \end{tabular} & 25 & 60 & 71.7 & 71.7 & [41] \\ \hline t-BuOK/t-BuOH catalyst & 36:1 & \begin{tabular}{c} catalyst-to-oil \\ molar ratio 0.1 \\ \end{tabular} & 28 & 60 & \begin{tabular}{c} 78.3 \\ about 90 \\ 93 \\ 94.8 \\ \end{tabular} & \
\begin{tabular}{c} [42] \\ [43] \\ [44] \\ [45] \\ \end{tabular} \\ \hline Lipozyme RM IM & 32:1 &
\begin{tabular}{c} 13\% (from oil mass) \\ \end{tabular} & 20 & 2520 (42 h) & 54.6 \(\pm\) 0.14 & 60.68 \(\pm\) 0.95 & [43] \\ \hline \end{tabular}
\end{table} 
Table 1: Summary of studies on using methyl formate for intereesterification of rapeseed oil. used potassium tert-butoxide and 1 M potassium tert-butoxide in tetrahydrofuran for intereesterification of rapeseed oil with methyl formate. The process was carried out under the same conditions: catalyst-to-oil molar ratio of 0.08, molar ratio of methyl formate-to-oil of 18:1, temperature 27 \({}^{\circ}\)C, and duration 60 min. The amount and yield of the esters were practically the same, both with and without co-solvent tetrahydrofuran. The yield of methyl esters were 71% without co-solvent and 71.7% with co-solvent tetrahydrofuran [41]. [PERSON] et al. [42] found that the optimal catalyst-to-oil molar ratio is 0.1, when catalyst tert-butoxide in tert-butanol is used for the intereesterification of rapeseed oil. The rapeseed oil methyl ester (RME) yield of 94.8% was obtained at a methyl formate-to-oil molar ratio of 80:1, temperature of 28 \({}^{\circ}\)C, and duration of 60 min [42]. [PERSON] et al.