# Synthesis of Biodiesel by Interestricification of Triglycerides with Methyl Formate
## 2 Intereesterification of Triglycerides with Methyl Formate
### Influence of Methyl Formate-To-Oil Molar Ratio on the Product Yield  
The intereesterification reaction, similar to the reaction of the conventional transesterification used in the production of biodiesel, is reversible. The higher yield of the product is obtained by using a quantity of the transesterification or intereesterification agent higher than the equivalent, i.e., by increasing the molar ratio of transesterification or intereesterification agent and oil (Figure 1). In the conventional synthesis of biodiesel, the molar ratio of methanol-to-oil most often used is 6:1.  
The molar ratio of methyl formate-to-oil is very important for obtaining maximum levels of esters and triformylglycerol. The oil intereesterification reaction requires three moles of methyl formate per mole of triglycerides, i.e., a minimum molar ratio of 3:1 (Figure 1).  
However, an excess of methyl formate is necessary to obtain a higher product yield. In triglyceride intereesterification studies, the molar ratio of methyl formate-to-oil ranged from 18: 1 to 80: 1, depending on the used catalyst and process conditions. For intereesterification of rapeseed oil, taking a molar ratio of 18:1 methyl formate-to-oil and using chemical catalysts, 71-78.3 wt.% rapeseed oil methyl ester content was obtained [37; 41; 42]. [PERSON] et al. investigated the influence of various molar ratios of methyl formate and oil on the efficiency of the intereesterification process and found that increasing the molar ratio also increases the content of esters. At a molar ratio of 18:1, the ester content in reaction product was 78.3 wt.%; when the molar ratio was 42:1, the ester content of 93 wt.% was obtained. At an even higher molar ratio, a slightly higher content of rapeseed oil methyl esters was obtained; at a molar ratio of 80:1, the ester content of 94.8 wt.% was determined. Researchers stated that the optimal molar ratio of methyl formate-to-rapeseed oil is 42:1-51:1 [42]. The results of the studies showed that the high yield of products is obtained only by taking a high molar ratio of methyl formate-to-oil. Similar trends have also been observed in the study of the effectiveness of the chemical intereesterification process using other carboxylate esters. At a methyl acetate-to-oil molar ratio of 18:1, triglycerides are fully converted to intermediates, and only when a 50:1 molar ratio is used are the intermediates converted to a final product [63]. [PERSON] et al. refers to a slightly lower optimal molar ratio for intereesterification using ethyl acetate, which reaches 11:1 [48].  
Meanwhile, the biotechnological process of intereesterification resulted in high ester yields using a smaller excess of methyl formate. [PERSON] et al. applied a biocatalytic process for the intereesterification of rapeseed oil with methyl formate. The influence of the molar on the intereesterification efficiency was investigated by changing the molar ratio from 6:1 to 40:1. The optimum molar ratio of methyl formate-to-oil was found to be 32:1 using the enzyme catalyst Lipozyme RM IM to obtain an ester yield of 60.68 \(\pm\) 0.95%. Increasing the molar ratio by more than 32:1 was not appropriate because the product yield increased insignificantly [43].  
Similar trends have been observed in the application of the biotechnological method for oil intereesterification with other types of carboxylate esters. The results of numerous studies by scientists who analyzed the biotechnological process of intereesterification of oil using methyl acetate coincide that the optimal molar ratio is 12:1 [19; 21; 36]. The results obtained by [PERSON] et al. (2010) are somewhat different, which showed that a 20:1 molar ratio is required for the interetification of olive oil with methyl acetate [23]. Meanwhile, when using ethyl acetate for the intereesterification of triglycerides, a high yield of esters was obtained, at a molar ratio 6:1 to 12.6 [19; 26; 62].