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United States Department of Agriculture

Agricultural Research Service

Title: Monitoring of Biodiesel Oxidation

Author
item Knothe, Gerhard

Submitted to: Annual Meeting and Expo of the American Oil Chemists' Society
Publication Type: Abstract Only
Publication Acceptance Date: May 8, 2002
Publication Date: N/A

Technical Abstract: Biodiesel is defined as the mono-alkyl esters of a vegetable oil or animal fat. These esters are subject to the reactions the fatty acid chains can undergo. Among these reactions is oxidation and subsequent degradation, particularly of the more unsaturated components, upon exposure to air. Thus, oxidative stability is an important issue facing biodiesel as oxidation products may impair fuel quality and, subsequently, engine performance. Efficient analytical methods are therefore needed to analyze the oxidation status of biodiesel. Methods that have been used in the past include wet chemical procedures such as the peroxide value or physical property-based ones such as viscometry. Up to the present, spectroscopic methods have virtually never been applied to this problem. It is now shown that both nuclear magnetic resonance (NMR) and near- infrared (NIR) spectroscopic methods can be applied. In 1H- NMR, especially the signals of the protons attached to the unsaturated carbons are of interest as they decrease with increasing oxidation. The effect on the NIR spectra is of interest as NIR has previously been reported to be suitable for monitoring biodiesel production and fuel quality. Oxidation affects the NIR spectra found suitable for these purposes. The spectroscopic results can be related to other methods such as viscometry.

Last Modified: 12/21/2014
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