Evaluation of Ascorbic Acid and Acetic Acid As Catalysts in the Transesterfication of Virgin Soybean Oil

Biologically derived acids such as ascorbic acid and acetic acid may be used to catalyze the production of biodiesel in a supercritical fluid solvent.  The use of binary mixtures of supercritical carbon dioxide and methanol with the aid of an acid catalyst can facilitate the transesterfication reaction.  This may hold a potential advantage over non-catalytic supercritical methanol production of biodiesel due to methanol’s higher critical temperature than that of the critical temperature of binary mixtures of carbon dioxide and methanol.  The production of biodiesel using a ascorbic acid and acetic acid as a catalyst was evaluated in an agitated 500 mL Hastelloy C276 batch reactor.  Comparison experiments between sub-critical methanol , supercritical methanol , and supercritical methanol with a carbon dioxide cosolvent were performed between 175 °C and 250 °C.  Hold time was varied between 20 and 40 minutes and the methanol and soybean concentrations were varied.  The effect of temperature and concentration upon conversion will be discussed as well as a comparison between catalysts and use of binary mixtures of supercritical carbon dioxide.