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This thesis has studied the low-temperature atmospheric pressure plasma as a potential technological application for the degradation of waste oils. The study has been approached initially by investigating the degradation of oil in gas phase only, in order to understand the gas chemistry and elucidate the plasma-chemical degradation mechanism. Gaseous odourless kerosene and dodecane have been used as simulants to waste oil and their plasma-chemical degradation has been studied using a BaTiO3 packed bed plasma reactor and a gliding arc discharge reactor. Kerosene showed similar degradation behaviour to dodecane and the latter one was chosen as a surrogate to allow quantitative analysis. The dodecane plasma degradation efficiency and the distribution of end-gaseous products have been studied under these two reactors in different gas compositions. Optical emission spectroscopy was used to identify intermediate excited species and calculate the rotational and vibrational temperature profiles. Differences in the dodecane degradation gas chemistry between the packed bed and the gliding arc plasma are discussed and postulated mechanisms are presented for each condition. Gliding arc discharge demonstrates higher degradation efficiency and it will be used mainly for the plasma-liquid treatment. The plasma-liquid dodecane treatment is firstly studied using argon dielectric barrier discharge. The effect of different reactor configuration, humidity and temperature to the discharge characteristics and degradation efficiency will be discussed. The study of the liquid dodecane degradation is extended by using the gliding arc discharge. Using N2 and Ar in both dry and humid conditions for the batch treatment of dodecane, the degradation efficiency, gas chemistry and liquid chemistry are discussed and correlated to the gas chemistry observed during the plasma treatment of gaseous dodecane under the same conditions, in order to gain an overall understanding of the plasma-liquid clean-up process. Finally, the gliding arc plasma treatment of liquid dodecane is studied using the recycling method and shows a significant improvement to the degradation efficiency.

Thermal oil oxidation is an important reason for the engine oil degradation in trucks. Having a comprehensive model that includes all the influential factors while it is feasible for being implemented in the ECUs, was aimed for this work. Therefore, the chemical investigating of the problem leaded to propose a first kinetic model and its thermal analysis caused modelling the oil thermal behaviour. The latter was developed for four compartments: Bearings, turbocharger, piston cooling and oil sump in the oil path through the lubrication system, because the highest oil temperature happens due to friction, combustion of fuels and exhaust gas transportation. Independency from the design parameters of the compartments and simplicity of models for the ECU implementation caused to investigate two various modelling hybrid approach: physical modelling and control theory approach. The first one was done for the bearings and piston cooling, and showed a high level of complexity leading to switch to the second approach. The latter was applied for all compartments while it satisfied requested requirements. To adjust and evaluate the models, an experimental campaign was devoted to acquiring the needed parameters with consideration of the project budget. Also using the previous simulation and experimental efforts at the company provided a possibility to develop flow rate sub-models used in the thermal modelling. The proposed model for all compartments, well predicted the oil thermal behaviour for both stationary and dynamic operating conditions. A comparison between the experimental data for the oil in the oil sump and turbo charger was done to show the reliability of the related models in both stationary and transient statuses. For the bearings, the simulation data for stationary condition were applied as a reference. The modelled oil temperature after piston cooling was compared to a set of experimental data that presented the probable temperature in some conditions close to stationary operating points.

Superfícies anisotrópicas lisas e rugosas foram usadas para avaliar o efeito da rugosidade e da direção de acabamento na formação de MoS2 a partir de MoDTC em ensaios tribologicos lubrificados com óleos de motor completamente formulados. Igualmente foi avaliada a resposta de atrito de lubrificantes de motor usados em carros de passageiros e em testes de dinamômetro abastecidos com etanol (E100) e gasolina (E22). Encontrou-se que tanto a direção de acabamento quanto a rugosidade foram fundamentais na reação MoDTC - MoS2. A direção de acabamento influenciou na medida que carregamentos tangenciais geram respostas diferentes nos ensaios quando são realizados paralelos e perpendiculares às linhas de acabamento, dado que para os últimos apresenta-se maior deformação plástica das asperezas, o qual favorece a obtenção de superfícies livres de óxidos, que tem sido indicada como uma condição necessário para que aconteça a reação MoDTC - MoS2. Por esta razão os valores de coeficiente de atrito próprios da formação de MoS2 foram obtidos somente nas superfícies rugosas ensaiadas perpendiculares às marcas de acabamento. Para superfícies com valores de índice de plasticidade superiores a 1 e nos quais não são formados filmes com boas capacidades redutoras de atrito, como é o caso de ensaios realizados com óleos base (livres de aditivos), o coeficiente de atrito não depende da rugosidade e da direção de acabamento. Nos ensaios lubrificados com óleos usado, encontraram-se valores de coeficiente de atrito similares aos obtidos nas condições de lubrificação com óleo livres de aditivos, devido provavelmente à redução do MoDTC no lubrificante como tem sido identificado por diferentes autores. Quando foram comparados os óleos usados contaminados com etanol com os óleos usados contaminados com gasolina, encontrou-se maior oxidação nestes últimos. Mesmo que estas diferenças de oxidação dos óleos não significaram diferenças em termos de atrito, estas podem ser importantes na medida em que óleos mais oxidados podem favorecer o desgaste oxidativo. / Smooth and rough anisotropic surfaces were used to evaluate the influence of surface roughnesss and lay direction on the in-situ formation of MoS2 from MoDTC in tribological tests. Also, this work evaluated the friction response of engine lubricants which were used in passenger cars and dynamometer tests fueled both with ethanol (E100) and gasoline (E22). It was found that both the lay direction as the surface roughness were critical for the MoDTC -MoS2 reaction. The lay direction influence due to tangential loads generate different responses when tests were conducted along and across the lay, since the latter showed higher asperities plastic deformation , which favors free oxides surfaces, which has been indicated as a condition for the sequence by MoDTC formed MoS2. For this reason the friction coefficient values related to MoS2 were obtained only for tests conducted on rough surfaces and across the lay. For surfaces with plasticity index values greater than 1 and which are not formed films with good friction-reducing capabilities, such as the tests lubricated with base oil (free aditives), the friction coefficient does not depends on the surface roughness and lay direction. For the tests conducted with used engine oils, the friction coefficient values were similar to those obtained on tests lubricated with free additives oils, this could be related by MoDTC depletion in the lubricants as have been identified by different authors. Comparing the used oils contaminated with ethanol with the used oils contaminated with gasoline, higher oxidation was founded in the latter. Even if these differences in oil oxidation not meant differences friction, these may be important as more oxidesed oils can promote oxidative wear.

Superfícies anisotrópicas lisas e rugosas foram usadas para avaliar o efeito da rugosidade e da direção de acabamento na formação de MoS2 a partir de MoDTC em ensaios tribologicos lubrificados com óleos de motor completamente formulados. Igualmente foi avaliada a resposta de atrito de lubrificantes de motor usados em carros de passageiros e em testes de dinamômetro abastecidos com etanol (E100) e gasolina (E22). Encontrou-se que tanto a direção de acabamento quanto a rugosidade foram fundamentais na reação MoDTC - MoS2. A direção de acabamento influenciou na medida que carregamentos tangenciais geram respostas diferentes nos ensaios quando são realizados paralelos e perpendiculares às linhas de acabamento, dado que para os últimos apresenta-se maior deformação plástica das asperezas, o qual favorece a obtenção de superfícies livres de óxidos, que tem sido indicada como uma condição necessário para que aconteça a reação MoDTC - MoS2. Por esta razão os valores de coeficiente de atrito próprios da formação de MoS2 foram obtidos somente nas superfícies rugosas ensaiadas perpendiculares às marcas de acabamento. Para superfícies com valores de índice de plasticidade superiores a 1 e nos quais não são formados filmes com boas capacidades redutoras de atrito, como é o caso de ensaios realizados com óleos base (livres de aditivos), o coeficiente de atrito não depende da rugosidade e da direção de acabamento. Nos ensaios lubrificados com óleos usado, encontraram-se valores de coeficiente de atrito similares aos obtidos nas condições de lubrificação com óleo livres de aditivos, devido provavelmente à redução do MoDTC no lubrificante como tem sido identificado por diferentes autores. Quando foram comparados os óleos usados contaminados com etanol com os óleos usados contaminados com gasolina, encontrou-se maior oxidação nestes últimos. Mesmo que estas diferenças de oxidação dos óleos não significaram diferenças em termos de atrito, estas podem ser importantes na medida em que óleos mais oxidados podem favorecer o desgaste oxidativo. / Smooth and rough anisotropic surfaces were used to evaluate the influence of surface roughnesss and lay direction on the in-situ formation of MoS2 from MoDTC in tribological tests. Also, this work evaluated the friction response of engine lubricants which were used in passenger cars and dynamometer tests fueled both with ethanol (E100) and gasoline (E22). It was found that both the lay direction as the surface roughness were critical for the MoDTC -MoS2 reaction. The lay direction influence due to tangential loads generate different responses when tests were conducted along and across the lay, since the latter showed higher asperities plastic deformation , which favors free oxides surfaces, which has been indicated as a condition for the sequence by MoDTC formed MoS2. For this reason the friction coefficient values related to MoS2 were obtained only for tests conducted on rough surfaces and across the lay. For surfaces with plasticity index values greater than 1 and which are not formed films with good friction-reducing capabilities, such as the tests lubricated with base oil (free aditives), the friction coefficient does not depends on the surface roughness and lay direction. For the tests conducted with used engine oils, the friction coefficient values were similar to those obtained on tests lubricated with free additives oils, this could be related by MoDTC depletion in the lubricants as have been identified by different authors. Comparing the used oils contaminated with ethanol with the used oils contaminated with gasoline, higher oxidation was founded in the latter. Even if these differences in oil oxidation not meant differences friction, these may be important as more oxidesed oils can promote oxidative wear.

FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico / O presente trabalho descreve os resultados da avaliaÃÃo de duas cepas de bactÃrias isoladas a partir de um efluente contaminado com Ãleo, para degradar derivados do petrÃleo e produzir biossurfactantes. AtravÃs de estudos de suas caracterÃsticas morfolÃgicas, culturais, bioquÃmicas e fisiolÃgicas, as bactÃrias selecionadas, nomeadas preliminarmente cepa 03 e cepa 04, foram identificadas como Acinetobacter spp. e Bacillus spp., respectivamente. A capacidade biodegradativa dessas bactÃrias foi avaliada cultivando-as em meio mineral mÃnimo, contendo, sempre, um dos hidrocarbonetos a serem testados, como Ãnica fonte de carbono e energia. As duas bactÃrias degradaram o glicerol, a gasolina, o querosene e o diesel e, produziram biossurfactantes. De maneira geral, as bactÃrias mostraram melhor desempenho na presenÃa de glicerol, como confirmado pelas medidas de densidade celular e atividade emulsificante, enquanto o diesel foi o pior substrato para ambas as bactÃrias. A produÃÃo de biossurfactante foi avaliada medindo-se a sua capacidade para emulsificar o querosene. AtravÃs dessa tÃcnica, encontrou-se um porcentual de 50% de emulsificaÃÃo para os biossurfactantes produzidos pelas duas bactÃrias a partir de glicerol. O Bacillus spp., praticamente, nÃo cresceu e nÃo produziu biossurfactante quando cultivado em meio com diesel, sobrevivendo, contudo, na forma de esporos. A suplementaÃÃo dessa cultura com extrato de levedura 0,04%, entretanto, promoveu a estimulaÃÃo do crescimento e da produÃÃo de biossurfactantes, atingindo um percentual de 95% de emulsificaÃÃo. Os resultados das anÃlises dos biossurfactantes extraÃdos a partir das culturas com glicerol, por espectroscopia infravermelha e anÃlises de carboidratos e proteÃnas, sugerem as classes dos lipossacarÃdios e polipeptÃdios, para os biossurfactantes produzidos pelas bactÃrias Acinetobacter spp. e Bacillus spp., respectivamente. As duas bactÃrias se mostraram suscetÃveis ao calor, sendo destruÃdas à temperatura de 46 ÂC, 1 ppm de hipoclorito de sÃdio e pH abaixo de 5,0. Por outro lado, resistiram a 5% de NaCl, uma caracterÃstica desejÃvel para utilizaÃÃo dessas cepas em situaÃÃes de biorremediaÃÃo de ambientes marinhos contaminados com Ãleo. / The present work describes the results of the evaluation of two bacteria strains isolated from the oil polluted effluent, to degrade petroleum derivatives and to produce biosurfactants. Morphologic, cultural, biochemical and physiologic studies showed that these bacteria, previously denominated strain 03 and strain 04, could be identified as Acinetobacter spp. and Bacillus spp., respectively. The biodegradation potential of these bacteria was evaluated by cultivating them in mineral broth, containing, glycerol, gasoline, kerosene or diesel as the only source of carbon and energy. Both bacteria degraded glycerol, gasoline, kerosene and diesel and produced biosurfactants. In general, the bacteria showed better performances at glycerol presence, as confirmed by the measures of cellular density and emulsificant activity, while the diesel was the worst substrate to both bacteria. The biosurfactant production was evaluated by measuring bacteria capacity for emulsificating kerosene. The results showed an emulsification of 50% for the biosurfactants produced from glycerol by the bacteria. Bacillus spp., practically, did not grow and did not produce biosurfactant when cultivated in medium with diesel, surviving, however, in the spore form. The supplementation of that culture with 0.04 % of yeast extract, however, stimulated the growth and biosurfactants production, reaching 95% of emulsification. The results of the analyses of the biosurfactants extracted from the cultures with glycerol, by infrared spectroscopy and carbohydrate and protein analyses, suggest the classes of the liposaccharides and polypeptides for the biosurfactants produced by the bacteria Acinetobacter spp. and Bacillus spp., respectively. These bacteria were shown to be susceptible to heat, being destroyed at the temperature of 46 ÂC, at 1,0 mg/L of sodium hypochloride and pH below 5.0. On the other hand, they resisted to 5% NaCl, a desirable characteristic for use in marine bioremediation programs.