CHARACTERIZATION OF SOLUBLE MACROMOLECULAR OXIDATIVELY REACTIVE SPECIES (SMORS) FROM MIDDLE DISTILLATE DIELEL FUELS - THEIR ORIGIN AND ROLEIN INSTABILITY

Compositional characterization of a solid-phase material isolated by e xtraction from filtered liquid-phase diesel fuels is reported. This so lid-phase material (SMORS) is shown to be the product of reactive fuel constituents and intermediate to the formation of fuel insoluble slud ge. The composition of this material changes during blending processes and tends to become more oxygen-rich and thus more polar. Elemental a nalysis, average molecular weight, and pyrolysis mass spectral data ar e presented for SMORS from a number of representative blended fuels an d their blending stocks. SMORS has been shown to be made up of oxidize d trimers, tetramers and possibly higher n-mers of nitrogen-containing precursors originally present in the fuel. It is not possible to dete rmine the SMORS precursors in field aged fuel (such as those in this s tudy) since these precursors are essentially depleted from the fuel by the time very small amounts of SMORS have been formed.