Additives for Improving the Octane Number

A second series of additives comprises those that improve the octane number (see Chapter 5). We will examine in succession the role played by these additives, substances currently used, and the future prospects concerning additives in this area. 

Chemical families typical of surfactants that are effective in engine admission systems. 

Diesel fuels, like gasoline, are formulated with additives that affect the process of combustion, in this case to improve the cetane number. Diesel fuels also contain detergents for irijection systems as well as compounds for improving the fuel s low tempierature rheology. Finally, decreasing particulate emissions is a problem of increasing concern, but the mechanism of action to promote this effect is not clearly understood. 

Unlike spark-induced combustion engines requiring fuel that resists autoignition, diesel engines require motor fuels, for vhich the reference compound is cetane, that are capable of auto-igniting easily. Additives improving the cetane number will promote the oxidation of paraffins. The only compound used is ethyl-2-hexyl nitrate. 

Moreover, the same surfactant structures that favor dispersion of fuel droplets in the combustion chamber most iikely play a role in reducing particulate emissions. ( 

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