In this study, decant oil and a blend of Pittsburgh seam bituminous coal with decant oil were subjected to coking and co-coking in a laboratory-scale delayed coker. Higher yields of coke and gas were obtained from co-coking than from coking. Coal addition into the feedstock resulted in lighter overhead liquid. GC/MS analyses of gasoline, jet fuel, and diesel show that co-coking of coal/decant oil gave higher quantity aromatic components than that of coking of decant oil alone. Simulated distillation gas chromatography analyses of overhead liquids and GC/MS analyses of vacuum fractions show that when coal was reacted with a decant oil, the coal constituents contributed to the distillable liquids. To address the reproducibility of the liquid products, overhead liquid samples collected at the first, third, and fifth hours of experiments of 6 h duration were evaluated using simulated distillation gas chromatography and 1 H and 13 C NMR. NMR analyses of the liquid products showed that, even though there were slight changes in the 1 H and 13 C spectra, the standard deviation was low for the time-dependent samples. Simulated distillation gas chromatography showed that the yields of refinery boiling range materials (i.e., gasoline, jet fuel, diesel, and fuel oil cuts) were reproducible between runs. Fractionation of the overhead liquids into refinery boiling range materials (gasoline, jet fuel, diesel, fuel oil fractions) showed that the boiling range materials and chemical compositions of fractions were found to be reproducible.

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We present data that suggest that jet fuel smoke point and the formation of thermal oxidative deposit are linked by formation of a common intermediate, high molecular weight soluble macromolecular oxidatively reactive species (SMORS). Hardy and Wechter (Energy Fuels 1994, 8, 782-787) have previously observed that with diesel fuels containing unhydrotreated light cycle oil (LCO), the highest molecular weight fraction of SMORS can be conveniently quantified as an extraction-induced precipitate (EIP). These authors have also shown that for fresh diesel fuel, oxidatively stressed fuel EIP mass correlates well with results of accelerated storage stability determined by ASTM 5304. Consistent with this, data are presented that suggest EIP mass, from jet fuels oxidatively stressed in tubing bombs, correlates with mean thermal oxidative deposition in a flowing reactor. In addition, data are presented that suggest that for a polar compound doped oxidatively stressed jet fuel, EIP mass correlates with the total concentration of polar compounds doped into the fuel. Thus, for the first time the concentration of select polar aromatics has been directly linked with the formation of a deposit precursor (Energy Fuels 1994, 8, 782-787) and smoke point.

The formation of carbonaceous deposits on metal surfaces in fuel systems is a major concern for the development of advanced aircraft. This study examines the thermal stability behavior and carbon deposition and morphology of carbon deposits of thermally stressed coal-based jet fuels. These materials consisted of hydrotreated 1:1, 2:1, and 3:1 blends of refined chemical oil (RCO) with light cycle oil (LCO). Reactions were carried out in a thermal stressing reactor on an Inconel 718 surface at a 470 °C fuel temperature. Chemical compositions of jet fuel samples were determined using gas chromatography−mass spectrometry. In this work, it was found that jet fuels containing low amounts of sulfur and nitrogen and higher amounts of decalins and saturated cyclics gave lower carbon depositions at 470 °C. The quantity of carbon deposits formed was found to be independent of the RCO/LCO ratio. The morphology of carbon deposits and chemical composition were also examined. The RCO/LCO ratio in the blend changed the deposit nature and deposit surface coverage. It was also observed that, if two fuels have very similar chemical compositions but different sulfur and nitrogen concentrations, the carbon deposit surface coverage or deposit growth was different.