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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Bio-oils Research » Research » Publications at this Location » Publication #304612

Title: A comprehensive evaluation of the density of neat fatty acids and esters

Author
item Knothe, Gerhard
item Steidley, Kevin

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/22/2014
Publication Date: 8/14/2014
Citation: Knothe, G.H., Steidley, K.R. 2014. A comprehensive evaluation of the density of neat fatty acids and esters. Journal of the American Oil Chemists' Society. 91(10):1711-1722.

Interpretive Summary: The knowledge of properties of materials is important for developing applications of these materials, as well as designing processes and facilities that use these materials. One such property is density, which is related to the relative weight of a material. In this work, the density of materials known as fatty acid alkyl esters, which are derived from vegetable oils, is comprehensively evaluated. Fatty acid alkyl esters include fatty acid methyl esters, which are commonly used as biodiesel, a biogenic alternative to petroleum-based diesel fuel, as well as other purposes. For fuel purposes, density is also of significance for combustion modeling. Thus, the results presented here will lead to improved understanding of biodiesel performance, but also for the use of biodiesel and fatty acid alkyl esters for other purposes such as engineering of reactors. Consequently, the results are of direct interest to researchers and producers working with biodiesel and other fatty acid alkyl esters as well as other parties interested in these materials.

Technical Abstract: Density is one of the most important physical properties of a chemical compound, affecting numerous applications. An application in the case of fatty acid esters (biodiesel) is that density is specified in some biodiesel standards. In the present work, the density of fatty acid methyl, ethyl, propyl, and butyl esters, as well as triacylglycerols in the C8-C24 range, was determined in the 15-40 deg. C range with a densitometer utilizing the oscillating U-tube technique. Literature data on density are compiled and compared, showing that data for these compounds are incomplete with discrepancies existing in some cases. Besides known effects such as density decreasing with increasing chain length and increasing saturation, it is shown that trans fatty compounds exhibit lower density than cis fatty compounds. Density data for several saturated odd-numbered, C18, as well as C20 and C22, polyunsaturated fatty esters are reported for the first time. The density contribution of compounds with high melting points is predicted. An equation is given for the calculation of the density of mixtures.