Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 5, 2009
Publication Date: June 26, 2009
Citation: Knothe, G.H., Dunn, R.O. 2009. A Comprehensive Evaluation of the Melting Points of Fatty Acids and Esters Determined by Differential Scanning Calorimetry. Journal of the American Oil Chemists' Society. 86(1):843-856. Interpretive Summary: In this research, we determined how knowledge of the melting points of biodiesel components contributes to making a better biodiesel fuel. This is valuable information for determining which combinations of the fatty acids and alcohols that produce fatty esters need to be selected to make such a better biodiesel fuel. Different alcohols, and different fatty acids in the oil or fat that can be used to make biodiesel, give different properties to the components of biodiesel. One of the important properties is the melting point. The melting point affects the behavior of biodiesel at low temperatures including whether the fuel flows from the tank to the engine. This paper describes how the melting point depends on the fatty acid and the alcohol from which they are made. This information is important for determining which fatty acids and alcohols make a better biodiesel fuel and it can be used in designing an improved fatty acid composition of vegetable oils and biodiesel.
Technical Abstract: The melting point is one of the most important physical properties of a chemical compound and plays a significant role in determining possible applications. For fatty acid esters the melting point is essential for a variety of food and non-food applications, the latter including biodiesel and its cold-flow properties. In this work, the melting points of fatty acids and esters (methyl, ethyl, propyl, butyl) in the C8-C24 range were determined by differential scanning calorimetry (DSC), numerous of which for the first time. For some compounds for which melting points have been previously reported, data discrepancies exist and a comprehensive determination by DSC has not been available. Variations of the present data up to several EC compared to data in prior literature were observed. The melting points of some methyl-branched iso- and anteiso-acids and esters were also determined. Previously unreported systematic effects of compound structure on melting point are presented, including for T-9 monounsaturated fatty acids and esters as well as for methyl-branched iso and anteiso fatty acids and esters. The melting point of a pure fatty acid or ester as determined by DSC can vary up to approximately 1EC. Other thermal data, including heat flow and melting onset temperatures are briefly discussed.