Conversion of corn oil to alkyl esters

Abstract

Biodiesel is an alternative fuel for diesel engine. It is made from non-toxic, biodegradable, renewable resources, such as vegetable oils, animal fats or triglycerides. The most common process used to produce biodiesel is the transesterification reaction, also known as alcoholysis. In the transesterification reaction, triglycerides reacted with an alcohol to produce chemical compounds known as fatty acid alkyl esters (biodiesel). Glycerol is produced as the by-product in the transesterification reaction. The high cost of raw material and the process costs make the production of biodiesel more expensive than the petroleum diesel fuel. Transesterification reactions of pure corn oil and corn oil from Distiller’s Dry Grain and Solubles were done in a pressurized batch reactor using methanol and ethanol as the alcohol reactants. Two different homogeneous catalysts (sodium methoxide and sodium hydroxide) and one heterogeneous catalyst (zinc aluminate) were tested to find the one that leads to the higher conversion of triglycerides to alkyl esters. The higher conversion achieved was with pure corn oil and the homogeneous catalyst sodium methoxide. A kinetic study was conducted to compare the initial reaction rates of methanol versus ethanol. The study demonstrated that there is no significance difference of using ethanol instead of methanol as the transesterification alcohol. Kinetic constants of triglycerides are smaller than kinetic constants of diglycerides and kinetic constants of diglycerides are smaller than kinetic constants of monoglycerides for both alcohols tested.