Production of Biodiesel from Michigan Soybean Oil Using Supercritical Methanol with Acetic Acid

Biodiesel is an affordable and renewable transportation fuel. Within the United States it is commonly produced from soybean oil.  In conventional production of biodiesel, the transesterfication reaction is typically catalyzed in batch reactors with reaction times greater than 1 hour.  Supercritical methanol is an alternative to catalyzed biodiesel production resulting in significantly reduced reaction times at temperatures greater than 350 °C.  The addition of acetic acid enables the transesterfication reaction to proceed in supercritical methanol at lower temperatures, nearing methanol’s critical temperature of 240 °C. Lower temperatures could result in a decrease in the energy costs of supercritical methanol biodiesel production.  The effects of temperature, concentration of acetic acid, methanol concentration, and reaction time on the production of biodiesel from Michigan soybean oil were evaluated in an agitated 500 mL Hastelloy C276 batch reactor.  In addition, the effect of adding biodiesel as a recycle into the reactor to facilitate mixing was also evaluated.  The product composition was characterized using ASTM D6584.  The viscosity, acidity, and density of the biodiesel product were also evaluated.