Fuel aromaticity

Heavy residue conversion is linked to the demand for high quality diesel motor fuel (aromatics content 10%, cetane number 55) as well as to the demand for production of light fuel-oil having very low sulfur, nitrogen and metal contents. 

A Fuel Aromatics + NO B Filter Extract New Engine c Dilution Tunnel Sediment Extract... 

Conversion of heterocyclic aromatic compounds or other aromatic fuel components to paraffins by hydroprocessing can help increase the cetane number of diesel fuel. Fuel paraffins have significantly higher cetane number values than fuel aromatics. For this reason, the cetane number of ultra-low sulfur diesel fuel will typically be one to five numbers greater than higher-sulfur grade fuels. 

Low smoke and soot Fuel paraffins bum with less smoke than aromatic compounds and can provide a higher flame height without smoking. High fuel density indicates the presence of greater concentrations of fuel aromatics. Also, certain sulfur-containing compounds can bum to form lamp deposits. 

A widely accepted relationship exists between the cetane index of a distillate fuel and the total aromatic content. Typically, as fuel aromatic content increases, the fuel cetane index decreases. It is generally believed that distillate fuel containing >35% aromatics will have a cetane index <40. Likewise, fuel having <35% aromatics will have a cetane index >40. 

Heterocyclic aromatics in fuel such as pyridine, indole and condensed thiophene compounds are known to darken fuel color. They have also been shown to lead to an increase in the deposit forming tendencies of fuel. Aromatic peroxides can also react to form higher-molecular-weight, sludgelike material in fuel. 

Hydroprocess to reduce fuel aromatic and/or naphthenic-aromatic compounds. 

The cetane index of distillate fuel can be related to the aromatic content of the blend. As fuel aromatic content increases, the cetane index will typically decrease. A general relationship exists which relates a cetane index of 40 with a diesel fuel aromatic content of about 35%. 

Aromatic compounds are the products of incomplete combustion of fuels. Aromatics are the usual pollutants of the chemical, petroleum, and coal-pyrogenic industries. These compounds are permanently present in air. As for N02 in air, its presence is always sufficient. Air-sols of HC1 and H2S04 are also present. In addition to sulfuric acid, nitric acid (the second component of the nitrating mixture) is formed as a result of the following reaction ... 

It has been ascertained that the quantity of aromatics in fuels is an important factor affecting PAH emission. Many results however, indicate the inadequacy of total fuel aromaticity as a general predictor of PAH emission, especially for gasoline. In fact it has been shown that the kind of aromatics exert a great influence, and particularly that PAH emission increase with the increase of the molecular complexity of aromatics in fuels. Aromatics with 9, 10 or more carbon atoms increase PAH emission much more... 

Apart from the more simple emissions of aromatic compounds such as benzene, previous work has shown that the fuel aromatic content itself strongly influences the emissions of PAH (Candelli et al., 1974 and Gross, 1973). Fuel aromatic contents influence particle associated PAH emissions almost linearly and a 10% increase in aromatics has been shown to increase emissions of benzo(a)anthracene, benzo(a)pyrene and benzo(ghi)perylene by approximately 20% (Pedersen et al., 1980). As typical increases... 

Other factors like age of engine, fuel aromaticity, driving mode,... 

Note I—This test method is temporarily retained because the proposal to the U.S. EPA to control diesel fuel aromatics concentrations via a 40 Calculated Cetane Index minimum is based on the correlation between Test Method D 976 and aromatics concentration. Test Method D 4737 is the preferred method as estimator of cetane number. Test method D 976 is intended to be letter balloted for withdrawal from the book of standards in 1993. 

Chou, C.C. Riviere, J.E. Monteiro-Riviere, N.A. 2003. The cytotoxicity of jet fuel aromatic hydrocarbons and dose-related interleukin-8 release from human epidermal keratinocytes. 

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