The Production of Biodiesel in Carbon Dioxide

Biodiesel is a renewable alternative to replace fossil fuels. As a liquid fuel source, biodiesel can replace petroleum based fuels without requiring major modifications to existing infrastructure. Nowadays, one of the main methods for biodiesel production involves the conversion of triglycerides (TG) to form fatty acid alkyl esters (biodiesel) via transesterification with alcohol. Currently, the major catalyst for this production is the homogeneous basic catalyst. Although these basic catalysts can convert TG to biodiesel efficiently, they would also react with free fatty acid, which naturally accompanies TG in biostocks and forms soap, which would inhibit the yield of biodiesel. To avoid the negative effects from the saponification reaction, in this project, Nafion®, a heterogeneous acidic catalyst is used for producing biodiesel from TG via the transesterification reaction and using supercritical carbon dioxide to increase reaction kinetics and to decrease mass transfer resistances for both TG and catalysts between phases. In this work, we have determined that FFA is more favored in this system than TG. The presences of both water and FFA will not bring detrimental effect to the overall yield of biodiesel from TG.