June 22, 2008
June 22, 2008
June 25, 2008
Division Experimentation & Lab-Oriented Studies
13.252.1 - 13.252.11
Biofuels in the Classroom: Using the Biodiesel Process to Demonstrate Chemical and Physical Principles
Global environmental, economic, and political factors are generating worldwide interest in biofuel production. However, because biofuel production is still an emerging industry, the study of biofuels is not yet a mainstream topic in most academic programs. Considerable misinformation and confusion exist which impacts acceptance of some biofuels. On the other hand student and community interest in biofuels is extensive, providing a significant opportunity to present accurate information and data.
This paper presents a process demonstration that serves as an excellent starting point to describe the conversion of vegetable oil into biodiesel (or Fatty Acid Methyl Ester, FAME). The conversion of vegetable oil into biodiesel is a spontaneous and relatively robust catalyzed chemical process that can be easily adapted into an in-class demonstration or lab experiment using inexpensive equipment and supplies. The basic chemistry of the biodiesel conversion process is outlined to allow calculation of reactant and catalyst amounts, and an acid test procedure is shown which allows for more precise calculation of the catalyst amount. This demonstration addresses the most common biodiesel production problem, that of incomplete reaction equilibrium, and describes a two-step process that produces a more complete reaction. It can also be demonstrated how to use the same ingredients to convert the catalyst into a reactant to block the transesterification reaction and produce undesirable outcomes.
Though the basic demonstration can be easily performed, many levels of complexity can be incorporated into a lesson to demonstrate chemical principles, physical properties, and process constraints. Used as a lecture or lab experiment, this process demonstration may lead to lessons on topics such as balancing chemical reaction equations, converting molar relations into scalable volume measurements, reaction equilibrium and completion concepts, side reactions, and polar vs. nonpolar molecules. Fluid properties of specific gravity and viscosity change during the reaction, and temperature affects the rate at which these changes occur. The effect of these properties on process equipment design can be discussed and calculated, along with material compatibility issues.
Using the biodiesel process as a lecture demonstration or lab activity helps students better understand basic process chemistry and physical properties of fluids, gain experience with process design issues, and gain a better understanding of this biofuel.
Biodiesel is defined as "a fuel comprised of mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, designated B100" 1. The most common biodiesel molecule is a fatty acid methyl ester (FAME) derived from the transesterification of triglycerides in soybean oil or canola (rapeseed) oil. Biodiesel is formed by chemically splitting a triglyceride molecule in the presence of an alcohol. In splitting the fatty acids off of the triglyceride molecule, the high viscosity of the feedstock oil is reduced to nearly that of petroleum based #2 Diesel fuel. The
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