Production of Biodiesel Fuel by Transesterification of Triglycerides in the Presence of Sodium Pyrophosphate

The possibility of using anhydrous sodium pyrophosphate and its decahydrate in transesterification of triacyl glycerides (with sunflower and rapeseed oils as examples) with methanol to obtain biodiesel fuel was examined. As shown by gas-chromatographic analysis, at the vegetable oil to methanol ratio of 1: 12, temperature of 65°C, reaction time of 2 h, and catalyst concentration of no less than 6 wt %, the maximal yield of methyl esters of fatty acids (biodiesel) was 93 and 69% when using Na₄P₂O₇ and Na₄P₂O₇·10H₂O, respectively. The catalytic effect of sodium pyrophosphate in the transesterification of triacyl glycerides was attributed to its methanolysis with the formation of sodium methylate. Water present in sodium pyrophosphate decahydrate causes hydrolysis of the formed sodium methylate; therefore, the yield of methyl esters of fatty acids is lower than with anhydrous pyrophosphate. Anhydrous sodium pyrophosphate can be used repeatedly no less than five times without significant decrease in the yield of methyl esters of fatty acids. Sodium pyrophosphate can be recommended for use in transesterification with other esters and alcohols.