# Synthesis of Biodiesel by Interestricification of Triglycerides with Methyl Formate
## 2 Intereesterification of Triglycerides with Methyl Formate
### Influence of Process Duration on the Product Yield  
Duration is one of the most important factors influencing the yield of products obtained during the intereesterification process. [PERSON] et al. investigated the process of intereesterification of rapeseed oil with methyl formate using catalyst tert-butoxide in tert-butanol, varying the reaction time from 0 to 90 min [41]. The optimal reaction time was found to be 60 min, and the reaction yield depended mainly on the molar ratio of methyl formate-to-rapeseed oil.  
[PERSON] et al. [37] stated that two layers are formed during the intereesterification process of rapeseed oil; the upper one contains more fatty acid methyl esters (FAME), the lower one contains mono- (MFG), di (DFG), and triformylglycerides (TFG) and glycerol (G). The yield of FAME (yield of FAME (%) shows how much oil is converted to FAME) obtained was 88.3 wt.%, and the amount of FAME (FAME amount in the mixture of FAME and formyl glycerides) was 74.2 wt.% (Table 2).  
Scientists have conducted studies of intereesterification with other types of carboxylate esters, with reaction times of 20 min to 40 h, depending on the process conditions, using chemical catalysts [20, 34, 35, 36, 37]. It was found that 20 min is enough to obtain a 77% yield of ethyl esters during alkaline intereesterification with ethyl acetate [48]. Meanwhile, [PERSON] et al., using ethyl acetate, obtained a 90% yield of ethyl esters in 20 h. It can be stated that the intereesterification process is greatly influenced by all four factors (molar ratio, amount of catalyst, temperature, and duration), and a change in one of them can lead to changes in other factors, in order to obtain a higher yield of products [20].  
A greater influence of duration on the efficiency of the process is observed in the application of the biotechnological synthesis method, the optimal duration of which allows for obtaining a higher yield of esters, compared to the method of chemical catalysis, to be higher. [PERSON] et al. investigated the dependence of the effectiveness of intereesterification reaction on the reaction time. The reaction duration was varied from 6 to 48 h, at a molar ratio of methyl formate-to-oil of 32:1, an enzyme content of 13%, and temperature of 20 \({}^{\circ}\)C. It has been found that the yield of methyl esters increases with  
\begin{table}
\begin{tabular}{l l l l l l l l} \hline \hline \multirow{2}{*}{**FAME Yield, \%**} & \multicolumn{2}{c}{**wt.\%**} & \multicolumn{3}{c}{**Reference**} \\ \cline{2-7}  & **DFMG** & **MFDG** & **TG** & **DG** & **TFG** & **FAME** & \\ \hline
88.3 & 5.3 \({}^{\ast}\) & 1.3 \({}^{\ast}\) & 0 \({}^{\ast}\) & 0.2 \({}^{\ast}\) & 2 \({}^{\ast}\) & 74.2 \({}^{\ast}\) & [37] \\
71.7 \({}^{\ast\ast}\) & 8.3 & 5.5 & 3.3 & & & 71.7 & [41] \\  & & & & & 6 & 78.3 & [42] \\
60.68 \(\pm\) 0.95 & 7.63 \(\pm\) 0.18 & 14.85 \(\pm\) 0.21 & 10.52 \(\pm\) 0.09 & 13.56 \(\pm\) 0.17 & 54.6 \(\pm\) 0.14 & [43] \\ \hline \hline \end{tabular} \({}^{\ast}\) Calculated using mass of layers; \({}^{\ast\ast}\) The FAME yield was calculated as the percentage of experimentally obtained mass contents from the theoretically predicted values.  
\end{table}
Table 2: Percentage composition of reaction mixtures.  
increasing process time. During the 24 h, a yield of 60.68 \(\pm\) 0.95% of methyl esters was obtained. As the process time was extended, the ester yield increased insignificantly: for a process time of 30 h, the ester yield was 61.47 \(\pm\) 1.10%. During 42 and 48 h of enzymatic intereesterification, RME yields of 65.4 \(\pm\) 1.11% and 65.3 \(\pm\) 1.14% were obtained, respectively. It was concluded that the optimal reaction time is 42 h [43]. The results of the majority of studies using other types of carboxylate esters showed that the optimal reaction time is 12-48 h, in order to achieve the maximum yield of the product and using the enzymatic intereesterification process [21; 28; 29].