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Orientador: Massao Ionashiro / Banca: João Oimpio Tognolli / Banca: Eder Tadeu Gomes Cavalheiro / Banca: Lázaro Moscardini D'Assunção / Banca: Maria Inês Gonçalves Leles / Resumo: Foram sintetizados no estado sólido os compostos Ln-2-MeO-Bz, sendo que Ln representa os lantanídeos trivalentes e Y (III) e 2-MeO-Bz representa o 2-methoxibenzoato. Os compostos foram sintetizados por adição estequiométrica, sob agitação, do ligante nas respectivas soluções de cloretos ou nitratos de lantanídeos. A precipitação dos compostos só ocorreram quando as soluções foram parcialmente evaporadas em banho maria. A caracterização dos compostos foi realizada utilizando-se de métodos convencionais: difratometria de raios X pelo método do pó, espectroscopia de absorção na região do infravermelho, análise elementar e as técnicas termoanalíticas TG/DTG (termogravimetria / termogravimetria derivada simultânea) e TG - DTA (termogravimetria - análise térmica diferencial simultânea) e DSC (Calorimetria exploratória diferencial). Estas técnicas puderam dar informações sobre desidratação, modos de coordenação, comportamento térmico, estequiometria e estrutura dos compostos sintetizados. Com os resultados das curvas TG e da complexometria, pôde-se estabelecer a fórmula geral de cada composto sintetizado. Pela análise dos difratogramas de raios X foi observado que todos os compostos sintetizados são cristalinos e que os compostos de lutécio e itérbio são isomorfos. A observação dos espectros de infravermelho teórico e experimental sugerem uma coordenação bidentada sem equalização de cargas entre o 2-metoxibenzoato e os seus respectivos centros metálicos. As curvas TG-DTA e DSC forneceram informações inéditas e importantes sobre o comportamento e a decomposição térmica dos compostos sintetizados. / Abstract: Solid state Ln 2-MeO-Bz compounds, where Ln stands for trivalent La to Lu and Y (III) and 2-MeO-Bz is 2-methoxybenzoate, have been synthesized. The solid state compounds were prepared by stoichiometric relation adding slowly, with continuous stirring the ligand solution to the respective metal chloride or nitrate solutions. No precipitate was observed during the addition of sodium 2-methoxybenzoate; however the precipitate was obtained when the solution was evaporated in a water bath. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffraction, infrared spectroscopy, elemental analysis and complexometry, were used to characterize and to study the thermal behaviour of these compounds. The results led to information about composition, dehydration, coordination mode, structure, thermal behaviour and thermal decomposition of the isolated compounds. From TG curves and complexometry results, a general formula could be established for these compounds in the solid state. The X-ray powder patterns pointed out that the synthesized compounds have a crystalline structure without evidence concerning to the formation of isomorphous series, except the ytterbium and lutetium compounds. The experimental and theoretical infrared spectroscopy data suggest that 2-metoxibenzoate acts as a bidentate bond with an incomplete equalization of bond lenghts in the carboxylate anion. The TG-DTA and DSC curves provided previously unrerported information concerning the thermal behaviour and thermal decomposition of these compounds. / Doutor

The pyrolysis of sec-butyllithium in solution was studied in an attempt to understand the loss of stereo-specificity and the atypical kinetics that have been reported. Additionally, the effect of added lithium alkoxides was studied to determine their effects on the highly reactive sec-butyllithium substrate.

The MixAlco process uses an anaerobic, mixed-culture fermentation to convert lignocellulosic biomass to carboxylate salts. The fermentation broth must be clarified so that only carboxylate salts, water, and minimal impurities remain. Carboxylate salts are concentrated by evaporation and thermally decomposed into ketones. The ketones can then be chemically converted to a wide variety of chemicals and fuels. The presence of excess lime in the thermal decomposition step reduced product yield. Mixtures of calcium carboxylate salts were thermally decomposed at 450 degrees C. Low lime-to-salt ratios (g Ca(OH)2/g salt) of 0.00134 and less had a negligible effect on ketone yield. In contrast, salts with higher lime-to-salt ratios of 0.00461, 0.0190, and 0.272 showed 3.5, 4.6, and 9.4% loss in ketone yield, respectively. These losses were caused primarily by increases in tars and heavy oils; however, a three-fold increase in hydrocarbon production occurred as well. To predict ketone product distribution, a random-pairing and a Gibbs free energy minimization model were applied to thermal decompositions of mixed calcium and sodium carboxylate salts. Random pairing appears to better predict ketone product composition. For sodium and calcium acetate, two types of mixed sodium carboxylate salts, and two types of mixed calcium carboxylate salts, activation energy (EA) was determined using three isoconversional methods. For each salt type, EA varied significantly with conversion. The average EA for sodium and calcium acetate was 226.65 and 556.75 kJ/mol, respectively. The average EA for the two mixed sodium carboxylate salts were 195.61, and 218.18 kJ/mol. The average EA for the two mixed calcium carboxylate salts were 232.78, and 176.55 kJ/mol. In addition, three functions of conversion were employed to see which one best modeled the experimental data. The Sestak-Berggren model was the best overall. Possible reactor designs and configurations that address the challenges associated with the continuous thermal decomposition of carboxylate salts are also presented and discussed. Methods of fermentation broth clarification were tested. Flocculation showed little improvement in broth purity. Coagulation yielded broth of 93.23% purity. Filtration using pore sizes from 1 micrometer to 240 Daltons increased broth purity (90.79 to 98.33%) with decreasing pore size.

Made available in DSpace on 2014-06-11T19:35:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-07-18Bitstream added on 2014-06-13T20:06:29Z : No. of bitstreams: 1 siqueira_ab_dr_araiq.pdf: 1539576 bytes, checksum: 6e539e939ace621bbe4c448e761c8893 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Foram sintetizados no estado sólido os compostos Ln-2-MeO-Bz, sendo que Ln representa os lantanídeos trivalentes e Y (III) e 2-MeO-Bz representa o 2-methoxibenzoato. Os compostos foram sintetizados por adição estequiométrica, sob agitação, do ligante nas respectivas soluções de cloretos ou nitratos de lantanídeos. A precipitação dos compostos só ocorreram quando as soluções foram parcialmente evaporadas em banho maria. A caracterização dos compostos foi realizada utilizando-se de métodos convencionais: difratometria de raios X pelo método do pó, espectroscopia de absorção na região do infravermelho, análise elementar e as técnicas termoanalíticas TG/DTG (termogravimetria / termogravimetria derivada simultânea) e TG – DTA (termogravimetria - análise térmica diferencial simultânea) e DSC (Calorimetria exploratória diferencial). Estas técnicas puderam dar informações sobre desidratação, modos de coordenação, comportamento térmico, estequiometria e estrutura dos compostos sintetizados. Com os resultados das curvas TG e da complexometria, pôde-se estabelecer a fórmula geral de cada composto sintetizado. Pela análise dos difratogramas de raios X foi observado que todos os compostos sintetizados são cristalinos e que os compostos de lutécio e itérbio são isomorfos. A observação dos espectros de infravermelho teórico e experimental sugerem uma coordenação bidentada sem equalização de cargas entre o 2-metoxibenzoato e os seus respectivos centros metálicos. As curvas TG-DTA e DSC forneceram informações inéditas e importantes sobre o comportamento e a decomposição térmica dos compostos sintetizados. / Solid state Ln 2-MeO-Bz compounds, where Ln stands for trivalent La to Lu and Y (III) and 2-MeO-Bz is 2-methoxybenzoate, have been synthesized. The solid state compounds were prepared by stoichiometric relation adding slowly, with continuous stirring the ligand solution to the respective metal chloride or nitrate solutions. No precipitate was observed during the addition of sodium 2-methoxybenzoate; however the precipitate was obtained when the solution was evaporated in a water bath. Simultaneous thermogravimetry and differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffraction, infrared spectroscopy, elemental analysis and complexometry, were used to characterize and to study the thermal behaviour of these compounds. The results led to information about composition, dehydration, coordination mode, structure, thermal behaviour and thermal decomposition of the isolated compounds. From TG curves and complexometry results, a general formula could be established for these compounds in the solid state. The X-ray powder patterns pointed out that the synthesized compounds have a crystalline structure without evidence concerning to the formation of isomorphous series, except the ytterbium and lutetium compounds. The experimental and theoretical infrared spectroscopy data suggest that 2-metoxibenzoate acts as a bidentate bond with an incomplete equalization of bond lenghts in the carboxylate anion. The TG-DTA and DSC curves provided previously unrerported information concerning the thermal behaviour and thermal decomposition of these compounds.

Les incendies de tunnels sont des phénomènes violents, à l’évolution rapide qui engendrent la plupart du temps des dommages importants aux personnes et aux biens. La sécurité incendie dans les tunnels routiers est basée sur l’utilisation de modèles empiriques très simplifiés de description de l’évolution de la cinétique de développement de l’incendie. Ces modèles ne prennent cependant pas en compte le type de combustible impliqués dans le phénomène, tels que les polymères constitutifs des enveloppes des véhicules routiers, ni leurs réactivité en phase solide (décomposition thermique). Dans l’optique de faire évoluer la description de l’incendie en fonction des conditions ambiantes caractéristiques d’un tunnel, un modèle prédictif de la décomposition thermique des matériaux a été développé. Ce modèle mathématique a été construit sur la base d’une approche expérimentale à petite échelle faisant intervenir le dispositif du cône calorimètre à atmosphère contrôlée couplé à un spectromètre infrarouge à transformée de Fourrier. Trois matériaux ont fait l’objet d’une étude approfondie de leur décomposition thermique, en fonction de deux paramètres clés influençant la décomposition des solides lors d’un incendie de tunnel : la concentration d’oxygène ambiante et l’éclairement énergétique imposé aux matériaux. Les résultats obtenus pour les trois matériaux choisis (une mousse Polyisocyanurate, un Ethylène Propylène Diène Monomère et un Acrylonitrile Butadiène Styrène) ont été utilisés pour la construction de régressions polynomiales multifactorielles, méthode également connue sous le nom de méthodologie des surfaces de réponses.Le modèle permet de définir la réponse de la cinétique de décomposition (variable expliquée) et son évolution, en fonction de la concentration d’oxygène locale et de l’éclairement énergétique imposé à la surface d’un matériau (variables explicatives). La comparaison des résultats numériques et expérimentaux a alors montré la pertinence de ce type d’approche / Tunnel fires are severe phenomenon whose evolution, usually very fast, can lead to important damages to persons and properties. Tunnel fire safety is based on the use of empirical models, very simplified that describes the evolution of the fire kinetic. Nevertheless, these models does not take into account neither the type of material that are involved in the phenomenon, such as constitutive polymers of road vehicles nor their reactivity in solid phase (thermal decomposition). In order to provide an evolution of the fire description, function of the conditions usually encountered in a tunnel, a predictive model aiming to describe materials’ thermal decomposition has been developed. This mathematical model has been established on the basis of an experimental approach, at small scale, using the Controlled Atmosphere Cone Calorimeter coupled to a Fourier Transform Infrared Spectrometer. The thermal degradation of three different materials (Polyisocyanurate foam, Acrylonitrile Butadiene Styrene and Ethylene Propylene Diene Monomer) has been thoroughly assessed function of key parameters that drives the decomposition process during fire: oxygen concentration and heat flux imposed to the materials. Obtained results for the three materials have then been used to construct multifactorial polynomial regressions, using the methodology known as surface response methodology. The model allows defining the response of the decomposition kinetics (explained variable), function of both the oxygen concentration and the heat flux received at the surface of the material (explanatory variable). Comparisons between numerical and experimental obtained results show the relevance of this approach.

Dimethylsilene, generated from the thermal gas phase reaction of 1,1-dimethyl-1-silacyclobutane, reacts with alkynes to produce silacyclobutenes or acyclic silanes. The temperature dependence of the product ratios have been determined and the relative reactivities of three different alkynes toward the 1,1-dimethylsilene has been determined. 1-Hydrido-1-methylsilene has been generated by gas phase thermal decomposition from three different precursors. Trapping studies with butadiene and trimethylsilane lead to products expected from dimethylsilylene. The most plausible explanation for these observations is that hydridomethylsilenes undergo a facile isomerization to divalent dimethylsilylene. Cycloaddition of 1,1-dimethylsilene to allene at 600°C in a flow vacuum pyrolysis system affords the first synthesis of 2-methylene-1,1-dimethylsilacyclobutane and smaller amounts of six other products. For static pyrolysis at 421°C, the 2-methylene-1,1-dimethyIsilacyclobutane isomerizes to 1,1-dimethylsilacyclopentenes. The kinetics of gas phase thermal decomposition of cyclopropyltrimethylsilane has been studied over the temperature range, 689.6-751.1 K at pressures near 14 torr. The Arrhenius parameters for formation of allyltrimethylsilane are k_1(sec^-1)=10^14.3 ± 0.1 exp(-56.5 ± 0.2 kcal mol^-1/RT) and those for the formation of E- and Z-1-propenyltrimethyIsilane are k_2(sec^-1)=10^14.9 ± 0.3 exp(-61.9 ± 0.8 kcal mol^-1/RT). The difference between activation energies has been interpreted in terms of anchimeric assistance or the β effect of the silicon atom. The syntheses of 3-trimethylsilyl-1-pyrazoline and 1-trimethyl-2-pyrazoline are described. The thermal decomposition of either pyrazoline affords four different products along with elimination of a nitrogen molecule. It was suggested that the relative rates of methylene-hydrogen migration to radical centers α and γ to silicon are approximately equal. The thermal isomerization of 3-trimethylsilyl-1-pyrazoline to 1-trimethylsilyl-2-pyrazoline has been investigated kinetically at 65°C by proton NMR spectroscopy and the reverse reaction has been detected by gas phase pyrolysis.

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In this thesis, the thermal decomposition investigation of haloethanols namely 2-chloroethanol and 2-bromoethanol are reported both experimental and theoretical. Computational calculation of enthalpy of formation haloethanols using isodesmic and atomization reactions has also been reported. Finally, the chemistry of JP-10 ignition has also been investigated using shock tube. Chapter 1 gives a brief introduction to the experimental shock tube technique. Brief surveys of literature pertinent to haloethanols and JP-10 have also been discussed. The importance of thermal rate coefficient and detection techniques in shock tube chemistry is presented. Details of the theoretical methods used in the determination of thermal rate coefficients have been described at the end of the chapter. In Chapter 2, I have discussed experimental methods used in carrying out this work. The details of the experimental shock tube set-up employed in this work have been elaborated in this chapter. Kinetic simulations performed to understand the mechanism of chemical transformation of haloethanols at high temperature have also been presented. In chapter 3, thermal decomposition results obtained for 2-chloroethanol have been described. The kinetic data have been obtained in the temperature range of 930-1100 K behind the reflected shock wave in a shock tube. Analyses of pre and post shock mixture using FT-IR and gas chromatographic techniques are presented. Chemical kinetic simulation performed to simulate the product distribution is presented. The reduced kinetic model has also been presented which was obtained using the sensitivity analysis and was validated by comparison to the shock tube measurements. The details of the β-substitution effect have been shown. The kinetic parameters of the unimolecular elimination of HCl and H2O have been presented both experimentally and theoretically. Theoretical results were obtained by transition state theory using quantum chemistry calculations HF, MP2 (FULL) and B3LYP/6-311++G** level of theory. The details of intrinsic reaction coordinate calculation and potential energy surface calculations have also been described. These experimental and theoretical results suggest that the rate of HCl elimination is faster than that of H2O and HOCl elimination reaction. In chapter 4, I have reported thermal decomposition results obtained for 2-bromoethanol. The kinetic data have been obtained in the temperature range of 910-1102 K behind the reflected shock wave in a shock tube. Analyses of pre and post shock mixture using FT-IR and gas chromatographic techniques are discussed. Chemical kinetic simulation performed to simulate the product distribution is presented. The details of the β-substitution effect are explained. Both experimental and theoretical kinetic parameters of the unimolecular elimination of HBr and H2O have been presented. Theoretical results were obtained by transition state theory using quantum chemistry calculations at the HF, MP2 (FULL) and B3LYP/6-311++G** level of theory. The intrinsic reaction coordinate calculation and potential energy surface have been investigated in details. From this experimental and theoretical studies, it has been concluded that the rate of HBr elimination much faster than that of H2O. However, the experiments show that the rate of HOBr elimination is faster than that of the H2O. In chapter 5, I have reported the computational calculation of enthalpy of formation of haloethanols. The enthalpy of formation of haloethanols of the general formula XC2H4OH were calculated by the HF, MP2, B3LYP, G2, G3, G2MP2, G3B3, G3MP2B3, CBS-Q, CBS-QB3 and CCSD/cc-pVDZ level of theories applying isodesmic and atomization reactions. Results obtained using the Benson’s group and bond additivity methods have also been described at 298.15 K and at 1 atm in the gaseous state. In chapter 6, ignition delay measurement on neat jet propellent-10 (JP-10) and JP-10 + Triethyl amine (TEA) mixture have been reported. The JP-10 (Exo-tetrahydrodicyclopentadiene, C10H16) ignition delay times were measured behind a single pulse reflected shock wave in a shock tube. Experiments were performed over high temperature, high pressure, and three equivalence ratio and for different composition. It has been shown that the TEA can reduce the ignition delay of JP-10. A higher level quantum chemistry calculation has also been presented that were performed to obtain the bond dissociation energies of C-H bonds in JP-10. Chapter7 is the concluding chapter where the main work done in this thesis is summarized and future direction is presented.

Master of Science / Department of Mechanical and Nuclear Engineering / Mohammad H. Hosni / Byron W. Jones / Gas turbine engine oil is contaminating the bleed air of an aircraft with enough frequency and intensity that health concerns are of public interest. While previous work measured micro particles and used only a simulator, this work mainly consists of measurements in the nanoparticle and ultrafine range using both the simulator and two different gas turbine engines. No previous research has been conducted using working jet engines to simulate a bleed air system and characterize the oil particulate contamination. Oil was injected into a bleed air simulator and an Allison 250 CC18 turbine engine in order to observe the particle size distributions resulting from thermal degradation and was measured with three particle sizing counters and an FTIR. The aerosol size distributions are given for various temperature and pressure ranges consistent with the process conditions associated with the bleed air in a commercial aircraft. Particle sizes of approximately 80nm to 100nm were observed at temperatures over 200°C while particles similar to injection distributions and smaller than measureable size were observed at lower power settings. Temperature is thought to be the controlling factor affecting particle size above 200°C while blade shear is likely the dominant factor for lower temperatures. The bleed air simulator produced results similar to the gas turbine engine results at higher temperatures, but did not replicate the size characteristics at lower temperatures. The observed particles are ultrafine and situated in the size range that may impact health safety more than larger particles.