Heptamethylnonane

The quality of diesel fuel is measured using the cetane number, a measure of the tendency of a diesel fuel to knock in a diesel engine, and the scale, from which the cetane number is derived, is based on the ignition characteristics of two hydrocarbons (1) n-hexadecane (cetane) and (2) 2,3,4,5,6,7,8-heptamethylnonane. 

Either primary or secondary reference fuels can be utilized in the cetane engine when determining the cetane number of distillate fuel. Primary reference fuels are n-cetane and heptamethylnonane. Secondary reference fuels are identified as T Fuel and U Fuel. The characteristics of each of these fuels are outlined in TABLE 4-7. 

This number is determined from the percentage of n-cetane which must be mixed with heptamethylnonane to give the same ignition performance as the fuel being tested. The cetane number can be obtained by using the following calculation ... 

Cetane Number—The ignition quality of a diesel fuel measured using an engine test specified in ASTM Method D 613. Cetane number is determined using two pure hydrocarbon reference fuels cetane, which has a cetane rating of 100 and heptamethylnonane (also called isocetane), which has a cetane rating of IS [2.2]. 

Ghoshal, S., Ramaswami, A., and Luthy, R. G. (1996 ) Biodegradation ofNapthalene from Coal Tar and Heptamethylnonane in Mixed Batch Systems, Environmental Science Technology, 30, 1282-1291. 

Triton X-100 completely prevented mineralization of hexadecane dissolved in heptamethylnonane Surfactant prevents bacterial adherence to solvent-water interface or affects cell membranes 26... 

The cetane number of a diesel fuel is defined as the whole number nearest to the value determined by calculation from the percentage by volume of normal cetane (cetane No. 100) in a blend with heptamethylnonane (cetane No. = 15) which matches the ignition quality of the test fuel when compared by this method. The matching blend percentages to the first decimal are inserted in the following equation to obtain the cetane number ... 

Additionally, significant variations of the standard deviation values were observed with respect to the individual compounds. The precision of S13C-values of n-alkanes, 2,2,4,4,6,8,8-heptamethylnonane, fatty acid methyl esters, phthalates and musk fragrances was generally acceptable down to amounts of approx. 5 ng with standard deviation values below 1.0 %o. On the contrary, already at the 25ng- and lOng-levels the stable carbon isotope ratios of the chlorinated compounds (CI5- and Cf,-benzene, Clfi-butadiene) as well as of tetrabutyl tin were measured with high standard deviations between 0.8 %o and 3.2 %o. 

In order to discern the discussed Elbe marker compounds from nonmarker substances several nonspecific contaminants were analysed additionally. These contaminants include galaxolide, tonalide, tri- -butylphosphate, 2,4,4-trimethylpentane-l, 3-dioldi-Ao-butyrate (TPDB) and 2,2,4,4,6,8,8-heptamethylnonane (HMN). No significant accumulation of these compounds was observed at sampling locations mainly influenced by either the Elbe river or the Ems and Weser rivers. 

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