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United States Department of Agriculture

Agricultural Research Service

Title: Precombustion and Cetane Improvement of Fatty Compounds

Author
item Knothe, Gerhard

Submitted to: Commercialization of Biodiesel Producing a Quality Fuel
Publication Type: Abstract Only
Publication Acceptance Date: July 10, 1997
Publication Date: N/A

Technical Abstract: Biodiesel, defined as the mono-alkyl ester derivatives of vegetable oils and animal fats, consists of the esters of various fatty acids. These fatty esters have different cetane numbers, i.e ignition delay time when injected into the combustion chamber of a diesel engine. The cetane numbers depend on the structure of the fatty ester. Structural features influencing cetane numbers include the number of methylene (CH2) groups in the chain of the fatty compound as well as the ester moiety and number and position of double bonds in the chain of the fatty compound. Several compounds have been identified that raise the cetane numbers of various fatty compounds by different amounts depending on their structure. This finding may offer the possibility of tailoring the cetane improver to the predominant fatty compound in the biodiesel fuel being used. Precombustion studies show that a possible explanation for differing cetane numbers may be the intermediate species formed upon injection of a fuel into the combustion chamber but prior to ignition. These intermediates have low cetane numbers, thus lowering the cetane number of the fatty compound. The intermediates formed can depend on the structure of the fatty compound.

Last Modified: 9/21/2014
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