A Continuous Process for the Conversion of Vegetable Oils into Methyl Esters of Fatty Acids

A continuous process for the transesterification of triglycerides to methyl esters was investigated in a pilot plant. The process was equipped with a motionlerr and a high-shear mixer. The experimental studies explored variations in the mixing intensity, stcichionetry, and catalyst concentration on the overall conversion. The combined as well as individual effect of mixers was examined. The developed process resulted i n high conversions of vegetable oils into methyl esters. Conversion oi triglycerides to methyl eslers i n excess of 98% was achieved. Larger excess amounts of alcohol favored higher conversions. The motionless and high-shear mixers each provided adequate mixing for the process. Higher catalyst concentrations resulted in higher conversions but increased the solublity of methyl esters in the glycerol layer. This reduced the amount of rrethyl esters separated by gravity settling. JAOCS 75, 1775-1 783 11998). Esters of fatty acids have shown the greatest potential as alternative diesel fuels, due to improved viscosity relative to the triplycerides. The viscosity of vegetable oils is reduced from about 10-15 times that of No. 2 diesel fuel to about twice that of No. 2 diesel for methyl esters. which is low enough to be used as diesel fuel. Other physical properties of fatty acid merhyl esters, such as cloud point and pour poiot, are considerably higher than No. 2 diesel fuel, which limits their use as an alternative to diesel fuel. However, up to 30 vol% of methyl esters in diesel fuel does not significantly changz the cold-flow properties of the fuel (6,7). Studies have also shown that engines running on methyl esters emit slightly lower amounts of hydrocarbons and CO and ligniiicantly lower particulates (8). The NO, emissions, however, are higher for methyl esters (8.9). Transesterification of vegetable oils and animal fats is the