Biodiesel Synthesis and Evaluation: An Organic Chemistry Experiment

摘要

Recent environmental regulations regarding diesel fuel standards and the role the Midwest may play in future fuel production provides an opportunity to relate principles of organic chemistry to everyday life. Biodiesel is the transesterification product of triglycerides of vegetable oils with methanol to form fatty acid methyl esters (FAMEs). The resultant FAME fuel has decreased viscosity compared to vegetable oil and fuel properties similar to petroleum-based diesel fuel. In this two week lab sequence students synthesize and evaluate fatty acid methyl esters from simulated waste vegetable oil. To maximize product, students determine weight percent of free fatty acid in the sample and convert the acids to FAMEs via acid-catalyzed Fischer esterification. After conversion of FFA, the remaining mono-, di-, and triglycerides in the waste vegetable oil are converted to FAMEs by base-catalyzed transesterification. Finally, the completeness of the conversion product is determined indirectly by analysis of total, free, and combined glycerol in the final product by stoichiometric oxidation of vicinal alcohols by periodic acid. By determining the weight of glycerol in a specific weight sample of product biodiesel, the student determines whether the glycerol concentration is low enough to meet the specifications for marketable biodiesel.