Diesel fuel nitrogen compounds

Nitrogen, sulfur, oxygen (NSO) compounds These organic non-hydrocarbon compounds are found in crude oils and in various refined products. The sulfur heteroatom compounds such as thiophene and dibenzothiophene are found in motor spirits and diesel fuels. Other compounds such as pyrrole (nitrogen) and benzofuran (oxygen) are also prevalent in crude oils and its products. 

Many GTL-derived fuels are being considered for blending with gasoline and diesel to achieve emission reductions of particulate matter (PM), carbon monoxide (CO), nitrogen compounds (NOx) and nonmethane hydrocarbons (NMHC). The most promising fuels converted from natural gas are methanol and ethers such as dimethyl ether (DME) and mcthyl-t-bntyl ether (MTBE). 

Diesel fuel is produced by distilling raw oil, which is extracted from bedrock. Diesel is a fossil fuel, consisting of hydrocarbons with between 9 and 27 carbon atoms in a chain, as well as a smaller amount of sulfur, nitrogen, oxygen and metal compounds. It is a general properly of hydrocarbons that the autoignition temperature is higher for more volatile hydrocaibons. The hydrocarbons present in the diesel fuels include alkanes, naphthenes, olefins and aromatics. 

Nitrogen compounds in diesel fuel and middle distillates can be selectively detected by chemiluminescence. Individual nitrogen compounds can be detected down to 100 ppb nitrogen. 

The next important parameter of diesel fuel is stability or storage stability. As fuel ages, it can become unstable and form insoluble particulates that accumulate and eventually end up on the fuel filter. For the most part, instability involves the chemical conversion of precursors to compounds of higher molecular weight with limited fuel solubility. The precursors are certain nitrogen and/or sulfur containing compounds, organic acids, and reactive olefins. The conversion process often involves oxidation of the precursors. Certain dissolved metals, especially... 

In all cases, the high sulfur content of the charges has been reduced to neghgible values in the naphthas and acceptable values for the diesel fuel. Furthermore, nitrogen compounds are almost completely eliminated from the products. Two very serious catalyst poisons, arsenic and lead, are shown to have been decreased to practical concentrations. Finally, the burning quality of the diesel fuel, as shown by the cetane number has been improved very considerably. 

Hsu et al. [68] and Mao et al. [69] examined the nitrogen-containing heterocyclic compounds in diesel fuel and other processed petroleum products. A combination of normal-phase HPLC and chemical ionization MS showed the presence of indole, carbazole, and benzocarbazole with varying degrees of methylation up to four. 

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