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United States Department of Agriculture

Agricultural Research Service

Title: Cetane Numbers, Cetane Improvement and Precombustion of Fatty Compounds in Biodiesel

Author
item Knothe, Gerhard

Submitted to: Biomass for Energy and Industry European Conference and Technology Exhibit
Publication Type: Abstract Only
Publication Acceptance Date: June 11, 1998
Publication Date: N/A

Technical Abstract: Biodiesel fuels (vegetable oils and animal fats and their derivatives, especially methyl esters) still pose some technical problems when used as alternative fuels in a diesel engine. Among these problems is the reduction of exhaust emissions such as NOx in order to meet increasingly stringent environmental regulations. NOx emissions are of particular concern because they are a precursor of ozone, a major component of smog. To solve the emissions problems, several aspects are being evaluated. Certain diesel fuel additives termed cetane improvers are known to decrease NOx emissions in conventional diesel fuel. Cetane improvers having different effects on various fatty compounds have now been identified, thus opening the possibility of tailoring the cetane improver to the predominant fatty compound in a biodiesel fuel. These effects depend on the nature of the cetane improver and structural features of the fatty compounds such as number and position of double bonds. In some cases, cetane number trends, such as an increase with increasing number of CH2 groups in the ester moiety, were altered. The compounds formed in the initial phase of fuel injection into the combustion chamber before ignition begins (precombustion phase) were evaluated by gas chromatography - mass spectrometry. This evaluation has shown that low cetane numbers of intermediary species formed prior to fuel ignition may be a possible explanation for differing cetane numbers of fatty compounds.

Last Modified: 11/27/2014
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