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The implementation of stringent diesel engine emissions regulations is growing worldwide. The use of high cetane diesel fuels is a cost-effective option that can be used to reduce engine emissions. A direct comparison of heavy-duty diesel engine emissions for three different low sulfur diesel fuels treated with di-t-butyl peroxide and 2-ethylhexyl nitrate, at the same cetane level, were evaluated. Both the peroxide and the nitrate cetane improvement additive significantly reduced all regulated and unregulated emissions including the oxides of nitrogen (NOx) emission. Di-t-butyl peroxide shows a small advantage over ethylhexyl nitrate in reducing NOx in all the three fuels. Compatibility of the peroxide and the nitrate additives, when mixed in a fuel blend, has been demonstrated by cetane response and engine emissions for the fuel blend.

The implementation of stringent diesel engine emissions regulations is growing worldwide. The use of high cetane diesel fuels is one of the more cost effective options that can be used to reduce engine emissions. Both organic nitrates and peroxides are effective chemical cetane improvers. While, nitrate-based ignition improvers have enjoyed longstanding commercial use, peroxides have only found limited use. Peroxides are typically perceived as having detrimental effects on fuel stability. For most, but not all peroxides, this perception is correct. The poor fuel stability observed in fuels containing peroxides results from the formation of radical species via peroxide decomposition. A peroxide with sufficient stability to prevent radical formation will avoid fuel compatibility issues. A di-alkyl peroxide has been identified that has minimal impact on fuel quality. The thermal stability of this peroxide will be compared to that of ethylhexyl nitrate.

The effects on engine emissions resulting from the addition of oxygenated additives to the fuel, have been investigated using a low emissions, Detroit Diesel Corporation (DDC) Series 60 engine. The oxygenates evaluated were selected on a combined basis of their fuel blending properties and potential costs. Oxygenates of varying molecular structures were selected for evaluation. The test results show that particulate emissions are directly related to the concentration of oxygen in the fuel. The particulate reductions are accompanied by small increases in NO, emissions. In general, the addition of an oxygenate to the fuel reduces carbon monoxide and hydrocarbon emissions. Non-regulated aldehyde and ketone emissions are also reduced with the addition of an oxygenate. When a peroxide-based cetane improvement additive was added to the oxygenated fuel, an emission profile similar to that from a low aromatic fuel was obtained.

A direct comparison is made between a peroxide based cetane improvement additive and the conventional cetane improvement additive, 2-ethylhexyl nitrate. The relative cetane performance of the two additives in two low sulfur fuels has been determined. The engine emissions from fuels containing each two of the additives have been investigated using a low emissions, Detroit Diesel Corporation (DDC) Series 60 engine. The oxides of nitrogen emissions for the peroxide containing fuel were found to be lower than those from the nitrate containing fuel. Peroxides are typically associated with having a detrimental effect on fuel quality. This issue has been addressed in terms of how this peroxide effects the carbon residue, oxidative stability, and elastomer compatibility of the fuel. The temperatures to which fuel is exposed in the injectors is increasing with the new low emissions engine designs.