STUDIES OF THE ROLE OF HETEROATOMIC SPECIES IN JET FUEL THERMAL STABILITY: MODEL FUEL MIXTURES AND REAL FUELS

摘要

In this study we utilize oxygen consumption and deposition measurements of model fuel mixtures and real fuels to explore the role that heteroatomic fuel species, and their interactions, play during fuel autoxidation. A range of temperatures, oxygen consumption regimes, and flow environments are employed to provide results applicable over a wide range of fuel autoxidative conditions. The quartz crystal microbalance (QCM) provides a low temperature (140°C) static reactor environment for long reaction times (minutes to hours) with oxygen consumption and sensitive, in-situ deposition measurements. The JFTOT system provides a flowing environment at higher temperatures (260 to 300°C) and short residence times (seconds) which is modified with an outlet oxygen sensor measurement and quantitative deposition measurements via ellipsometry. These techniques are used to study model systems (Exxsol D80 with added heteroatom species) and real jet fuels to determine the role of heteroatomic species in jet fuel autoxidation and deposition. The QCM results demonstrate that nitrogen and sulfur species (e.g., indoles/anilines and sulfides) interact during jet fuel autoxidation to encourage deposit formation. The further addition of phenol species, which occur naturally in most petroleum-derived jet fuels, enables even greater deposit production. This behavior is confirmed in the JFTOT via addition of nitrogen and sulfur-containing species to medium and low sulfur jet fuels. Sample collection during autoxidation in the QCM with subsequent gas chromatographic (GC) analysis shows rapid sulfur autoxidation followed by a slow reaction of the nitrogen species to form deposit precursors, implying a step-wise reaction of sulfur oxidation products with nitrogen species to form deposit precursors. These results have important implications for production and mitigation of thermal stability degradation during fuel pipeline transport.