ASTM D3241 (Standard Test Method for Thermal Oxidation Stability of Aviation Turbine Fuels) measures the thermal oxidative stability of jet fuels under elevated temperature and pressure conditions. When jet fuels fail ASTM D3241, either at the refinery or in the distribution system, there can be supply disruptions and financial losses. Understanding the causes of poor thermal oxidative stability in jet fuels could help prevent or mitigate issues. In order to develop a deeper understanding of the molecular precursors that lead to ASTM D3241 failures, a number of analytical methodologies and data treatment techniques have been developed, applied, and reported here. Statistical analysis of LC/MS ESI data from jet fuels with varying thermal oxidative stabilities allows for the identification of molecules that are significant to ASTM D3241 failures. Differential statistical analysis of LC/MS ESI data from jet fuels before and after thermal oxidative stressing in a QCM reactor elucidates which significant molecules are being consumed during oxidation and which molecules are increasing in abundance. The analysis of thermal oxidative deposits that form during thermal oxidative stressing in the QCM reactor allows for the insight into the molecular components of the deposits. Attapulgus clay removes the polar molecules that lead to thermal oxidative stability issues in the refinery. Extraction of Attapulgus clay that has been used in a refinery to filter jet fuel with a series of solvents removes the polar molecules into a series of fractions. The subsequent analysis of the fractions by comprehensive GCxGC/MS leads to the identification of the different homologous series of molecules that are removed by the clay. The analyses developed and employed here are shown to be particularly useful for the analysis of trace polar nitrogen and oxygen containing molecules. Similar homologous series of molecules are identified across all of the different analyses. It is also clear from some of the analyses, along with previously reported data in the literature, that reactive sulfur-containing molecules are significant to poor thermal oxidative stability as measured by ASTM D3241 and to the formation of thermal oxidative deposits. There is still an opportunity to find methodologies to better characterize the sulfur species present and correlate them to the data that is reported here.

Made available in DSpace on 2015-04-17T14:49:13Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2457089 bytes, checksum: f62a3f2f2f07c35cf1267329a959219b (MD5) Previous issue date: 2009-09-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Overestimating nutritional tendency of the golden flaxseed instead of the brown one and considering that the roasting of seeds to deactivate antinutritional factors as an aggravating factor to the thermo-oxidation of fatty acid constituents, we aimed to characterize the seeds and oils of golden and brown varieties of flaxseed regarding nutrition, physical-chemical and thermo-oxidative stability. The influence of roasting on stability properties was evaluated by using chemical composition methods (humidity, ash, lipids, proteins, carbohydrates and soluble fibers), physical-chemical methods (iodine, acidity, saponification, peroxide, refractive index, percentage of free fatty acids, density and viscosity), spectroscopic methods (UV-visible and infrared), chromatographic (GC/ MS) and thermal analysis (TG and DSC). The seeds of both varieties were divided into two lots, the first was composed of raw seeds and the second was composed of roasted seeds at 160 ˚ C/ 15 minutes. The lots were equally divided and half was crushed and half was pressed to extraction of the oil. The raw flaxseeds showed similar chemical composition, however the golden seeds presented a higher content of protein, soluble sugars, lipid and polyunsaturated fatty acid contents. On the other hand, the brown seeds were higher on the ash, dietary fiber and monounsaturated fatty acid contents. The raw seeds of both varieties showed thermal and oxidative stability higher than 2 hours under 160 ˚C isotherm, indicating that the roasting does not cause thermo-oxidative changes in the seeds due to the presence of natural antioxidants. The applications of new thermic treatments, however, convert the organic compounds contained in roasted seeds, especially the fatty acid, susceptible to oxidation. Physical-chemical, spectroscopic and thermal data corroborate the results, which showed the highest thermal and oxidative stability of the degradation products of roasted seeds and toasted seed oils (OITi = 23 and 33 minutes for golden roasted seed oil and brown roasted seed oil, respectively) compared to the raw seeds and their oils (OITi = 20 minutes, for both varieties). / Diante da tendência de supervalorização nutricional da linhaça dourada em detrimento da marrom e considerando-se que a torrefação das sementes para inativação de fatores antinutricionais seja um fator agravante para a termo-oxidação dos ácidos graxos constituintes, buscou-se caracterizar as sementes e os óleos das variedades marrom e dourada de linhaça quanto aos aspectos nutricionais, físico-químicos e de estabilidade termo-oxidativa, e avaliou-se a influência da torrefação sobre tal estabilidade, utilizando-se métodos de composição química (determinação de umidade, cinzas, lipídios, proteínas, carboidratos solúveis totais e fibras), métodos físico-químicos (índices de iodo, acidez, saponificação, peróxido, refração, percentual de ácidos graxos livres, densidade e viscosidade), espectroscópicos (UV-visível e infravermelho), cromatográficos (GC/MS) e de análise térmica (TG e DSC). As sementes de ambas as variedades foram divididas em dois lotes, sendo o primeiro constituído pelas sementes cruas e o segundo pelas sementes torradas a 160 ˚C/ 15 minutos. Em ambos os lotes, parte das sementes foram submetidas à trituração e outra parte à extração do óleo por prensagem a frio, com proporção de sementes de 1:1. As sementes cruas de linhaça apresentaram semelhanças quanto à composição química e ao perfil lipídico, apesar do maior teor de proteínas, açúcares solúveis totais, lipídios totais e AG poli-insaturados das sementes douradas. Por outro lado, as sementes marrons foram superiores quanto ao teor de cinzas, fibras totais e AG monoinsaturados. As sementes cruas de ambas as variedades apresentaram estabilidade térmica e oxidativa superior a 2 horas, sob isoterma de 160 ˚C, indicando que a torrefação não provoca alterações termo-oxidativas nas sementes, devido à presença de antioxidantes naturais. A aplicação de novos tratamentos térmicos, porém, torna os compostos orgânicos contidos nas sementes torradas, em especial os AG, sensibilizados e susceptíveis à oxidação. Essa ideia foi corroborada pelas análises físico-químicas, espectroscópicas e térmica, por meio das quais demonstrou-se a maior estabilidade térmica e oxidativa dos produtos de degradação das sementes torradas e dos óleos degradados das sementes torradas (OITi = 23 e 33 minutos, para OLDT e OLMT, respectivamente) em relação às sementes cruas e seus óleos (OITi = 20 minutos, para ambas as variedades).