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United States Department of Agriculture

Agricultural Research Service

Title: Monitoring a Progressing Transesterification Reaction by Fiber-Optic Near Infrared Spectroscopy with Correlation to (1)h-Nuclear Magnetic Resonance Spectroscopy

item Knothe, Gerhard

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 11, 2000
Publication Date: N/A

Interpretive Summary: Biodiesel is an alternative diesel fuel derived from vegetable oils such as soybean oil. It is made from vegetable oils through a reaction called transesterification. Biodiesel producers carrying out a transesterification reaction need to know if the reaction is successful and if the product meets prescribed fuel quality standards. Recent research showed that a method called near-infrared (NIR) spectroscopy using a device termed a fiber-optic probe is a rapid, low-maintenance, and cost- efficient alternative to the presently used analytical method named gas chromatography (GC) for this purpose. In this work, NIR was applied to samples taken from a progressing transesterification reaction. Besides, another analytical method called nuclear magnetic resonance (NMR) spectroscopy was applied to the samples. Evaluation showed that NIR and NMR results are in good agreement. Therefore, both methods can be used for assessing biodiesel fuel quality or monitoring the transesterification reaction. NIR will likely remain more attractive because of low cost and ease and rapidity of measurement.

Technical Abstract: Biodiesel is a promising alternative diesel fuel obtained from vegetable oils, animal fats, or waste oils by transesterifying the oil or fat with an alcohol such as methanol. In an extension of previous work, fiber-optic near infrared spectroscopy was used to quantitatively monitor the transesterification reaction (6 L scale) of a vegetable oil (soybean oil) to methyl soyate. The results were correlated with (1)H nuclear magnetic resonance spectroscopy. The method described here can be applied to the transesterification of other vegetable oils.

Last Modified: 4/22/2015
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