Fuel combustion additives: A study of their thermal stabilities and decomposition pathways

The purpose of this study was to evaluate whether a relationship exists bet ween thermal stabilities of selected fuel additives and their effectiveness as diesel fuel cetane improvers. The additives were 2-ethylhexyl nitrate, isopropyl nitrate, tetraethylene glycol dinitrate, di(tert-butyl) peroxide, and methylcyclopentadienyl manganese tricarbonyl. Rate constants and activ ation parameters were determined for the thermolysis of the neat additives as well as the additives dissolved in various solvents and fuels. In all ca ses, decomposition kinetics were first-order. Mass spectral analysis was us ed to identify products from the thermal decomposition of the additives in various solutions. Thermal stability, as measured by the kinetics of decomp osition, was not an accurate predictor of the effectiveness of the additive s as cetane improvers. The effectiveness of a given additive appeared to co rrelate to the degree of molecular fragmentation rather than to thermal sta bility.