Studies of the Role of Heteroatomic Species in Jet Fuel Thermal Stability: Model Fuel Mixtures and Real Fuels

摘要

Oxygen consumption and deposition measurements of model fuel mixtures and real fuels are used to explore the roles 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 degrees C) batch 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 degrees C) and short residence times (seconds) which is modified with both an outlet oxygen sensor and with 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, facilitates 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. These results, along with gas chromatographic (GC) analysis of samples collected during autoxidation in the QCM, show rapid sulfur autoxidation followed by a slower reaction of the nitrogen species to form deposit precursors, implying a stepwise reaction of sulfur oxidation products with nitrogen species to form deposit precursors. These results have important implications for fuel production strategies and mitigation of thermal stability degradation during fuel pipeline transport, storage, and use.