Orientador: Roy Edward Bruns / Dissertação (mestrado profissional) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-18T15:22:35Z (GMT). No. of bitstreams: 1 Araujo_JorgePauloDantasde_M.pdf: 2024692 bytes, checksum: d5669168a2ce24885a57c2fa7cf830b8 (MD5) Previous issue date: 2011 / Resumo: O processo de desenvolvimento de motores Diesel vem sendo cada vez mais estudado e aprimorado dentro da Indústria. A busca por ferramentas que possam reduzir o tempo de desenvolvimento e também otimizar o trabalho para atingir requisitos de desempenho, redução de consumo de combustível e limites de emissões cada vez mais restritivos é muito importante. Por esse motivo, o presente trabalho pretende contribuir com informações que podem conduzir ao conhecimento necessário para aplicação de planejamento multivariado, no processo de desenvolvimento de um motor Diesel, buscando uma diminuição no tempo para realizar esta atividade. Em uma primeira fase do trabalho, foram identificados quais os componentes (fatores) que deveriam ser estudados e também as variáveis de resposta, que no caso são consumo de óleo lubrificante e pressão de recirculação dos gases de combustão (pressão de carter). Após a definição dos componentes, foram selecionados quais os níveis dos fatores a serem estudados (no caso, mudanças geométricas dos componentes). Em seguida foi aplicada a metodologia de planejamento multivariado de experimentos (fatorial completo) para identificar qual o melhor compromisso entre as configurações estudadas visando os melhores resultados das variáveis de resposta. Ao final desta fase foi possível identificar a melhor configuração entre os componentes estudados e também um ganho substancial no tempo necessário para executar esta atividade. Já em uma segunda fase do trabalho, foi realizado um estudo verificando a influência das tolerâncias de especificação de projeto de alguns componentes considerados críticos para as mesmas respostas estudadas na fase 01 (consumo de óleo e pressão de carter). Através de um estudo fatorial fracionado foi possível identificar quais são as especificações críticas a serem controladas no processo produtivo para manter os valores de consumo de óleo e pressão de carter dentro dos padrões especificados para o motor em questão / Abstract: The Diesel engine development process has been increasingly studied and improved by industry. The search for tools that can reduce development time and also optimize the work to achieve performance requirements, fuel consumption targets and restrictive emission limits is very important. For this reason, this work aims to contribute with information that may lead to knowledge necessary for the application of multivariate planning in the development process of a Diesel engine, seeking a reduction in time to perform this activity. In the first phase of this work components (factors) that should be studied and also the response variables, which are lubricating oil consumption and pressure of combustion gas recirculation (carter pressure) have been identified. After the component definitions were made the factor levels were selected for study (geometrical changes in the components). Then multivariate statistical designs were applied (full factorial) to identify the best compromise among the levels studied in order to obtain the best results for the response variables. At the end of this phase it was possible to identify the best configurations for the components studied, which also resulted in a substantial gain in the time necessary to perform this activity. In a second phase of this work, a tolerance study was carried out on the influences of the geometrical design specifications of some components considered critical for the same responses studied in phase 1 (oil consumption and carter pressure). Through a fractional factorial study it was possible to identify the critical specifications to be controlled in the productive process to maintain the values of oil consumption and carter pressure within the defaults specified for the engine in question / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Automobilistica

Diesel fuel is composed of a complex mixture of hundreds of hydrocarbons that vary globally depending on crude oil sources, refining processes, legislative requirements and other factors. In order to simplify the study of this fuel, researchers create surrogate fuels with a much simpler composition, in an attempt to mimic and control the physical and chemical properties of Diesel fuel. The first surrogates were single-component fuels such as n-heptane and n-dodecane. Recent advancements have provided researchers the ability to develop multi-component surrogate fuels and apply them to both analytical and experimental studies. The systematic application of precisely controlled surrogate fuels promises to further enhance our understanding of Diesel combustion, efficiency, emissions and particulates and provide tools for investigating new and alternative engine combustion systems. This thesis employed analytical and experimental methods to develop, validate and study a library of multi-component surrogate Diesel fuels. The first step was to design a surrogate fuel to precisely match the physical and chemical properties of a full-range petroleum Diesel fuel with 50 cetane number and a typical threshold soot index value of 31. The next step was to create a Surrogate Fuel Library with 18 fuels that independently varied two key fuel properties: cetane number and threshold soot index. Within the fuel library cetane number ranged from 35 to 60 at three threshold soot index levels of 17, 31 and 48 (low, mid-range and high). Extensive ASTM fuel property tests showed that good agreement with important physical and chemical properties of petroleum Diesel fuel such as density, viscosity, heating value and distillation curve. An experimental investigation was conducted to evaluate the combustion, emissions, soot and exhaust particles from the petroleum Diesel fuel and the matching surrogate fuel. A fully-instrumented single-cylinder Diesel engine was operated with combustion strategies including Premixed Charge Compression Ignition (PCCI), Low-Temperature Combustion (LTC) and Conventional Diesel Combustion (CDC). For combustion, the ignition delay, low-temperature (first stage) and high temperature (second stage) heat-release matched very well. Gaseous emissions, soot and exhaust particles maintained good agreement as exhaust gas recirculation and combustion phasing were varied. This thesis demonstrated that fully representative Diesel surrogate fuels could be tailored with the proper blending of the following hydrocarbon components: n-hexadecane, 2,2,4,4,6,8,8-heptamethylnonane, decahydronaphthalene and 1-methylnaphthalene. It was also established that the volumetric blending fractions of these four components could be varied to independently control the fuel cetane number and threshold soot index while retaining the combustion, physical and chemical properties of full-range petroleum Diesel fuel. The Surrogate Fuel Library provided by this thesis supplies Diesel engine researchers and designers the ability to analytically and experimentally vary fuel cetane number and threshold soot index. This new capability to independently vary two key fuel properties provides a means to further enhance the understanding of Diesel combustion and design future combustion systems that improve efficiency and emissions. / El combustible diésel está compuesto por cientos de hidrocarburos cuya presencia y proporción varía dependiendo del origen del crudo, del proceso de refinado, de los requerimientos legislativos, y de muchos otros factores. Para evitar las dificultades que produce esta variabilidad y complejidad en su composición, en los estudios sistemáticos, los investigadores suelen trabajar con combustibles de sustitución, mucho más sencillos, pero que reproducen las propiedades químicas y físicas del gasóleo. Los primeros combustibles de sustitución estuvieron formados por un solo componente, como el n-heptano y el n-dodecano. Recientemente se han desarrollado combustibles de sustitución multi-componentes, que se aplican tanto a estudios experimentales como de modelado. La aplicación sistemática de combustibles de sustitución controlados con precisión es una vía prometedora para mejorar la comprensión de la combustión Diesel, su eficiencia, y sus emisiones y proporciona herramientas para la investigación de sistemas de combustión nuevos y alternativos. En esta tesis se han empleado métodos experimentales y de cálculo para desarrollar, estudiar y validar una librería de combustibles de sustitución multi-componentes. El primer combustible de sustitución se diseñó para reproducir con precisión las propiedades físicas y químicas de un gasóleo con número de cetano 50 y un índice de hollín umbral (TSI) de 31.El siguiente paso fue crear una biblioteca de combustibles de sustitución con 18 combustibles que pueden modificar independientemente dos propiedades clave del combustible: índice de cetano y TSI. En la biblioteca de combustibles el número de cetano osciló entre 35 y 60 con tres niveles de TSI iguales a 17, 31 y 48 (bajo, medio y alto rango). Los ensayos según la normativa ASTM demostraron una buena coincidencia con las propiedades del gasóleo como densidad, viscosidad, poder calorífico y curvas de destilación. Para comprobar la validez de la librería, se realizó un estudio experimental comparativo sobre el proceso de combustión, las emisiones gaseosas, hollín y partículas de un gasóleo y de su combustible de sustitución ajustado. El estudio se realizó con un motor monocilíndrico Diesel completamente instrumentado y operando con estrategias de combustión en premezcla parcial (PPCI) y de baja temperatura (LTC), además de la combustión Diesel convencional (CDC). Los parámetros de la combustión como el retraso al encendido y la liberación de calor tanto de baja como de alta temperatura se aproximaron muy bien. Las emisiones de gases, hollín y partículas también fueron similares al variar el nivel de EGR y la fase de la combustión. La tesis demuestra que se pueden encontrar combustibles de sustitución perfectamente representativos de un gasóleo corriente, en base a mezclas apropiadas de n-hexadecano, 2,2,4,4,6,8,8-heptamethylnonano, decahidronaftaleno y 1-metilnaftaleno. Asimismo, se concluye que variando la proporción de estos cuatro componentes se puede controlar independientemente el número de cetano y el índice de hollín umbral, a la vez que se mantienen las propiedades físico-químicas y de combustión del gasóleo. La librería de combustibles de sustitución definida en esta tesis es una herramienta a disposición de los investigadores para profundizar en el conocimiento de la combustión diésel y avanzar en el diseño de sistemas futuros de combustión con mejor rendimiento y menores emisiones. / El combustible Diesel està compost per centenars d'hidrocarburs, la presència i proporció dels quals varia depenent de l'origen del cru, del procés de refinat, dels requeriments legislatius, i de molts altres factors. Per a evitar les dificultats que produeix aquesta variabilitat i complexitat en la seua composició, en els estudis sistemàtics, els investigadors solen treballar amb combustibles de substitució, molt més senzills, però que reprodueixen les propietats químiques i físiques del gasoil. Els primers combustibles de substitució van estar formats per un sol component, com el n-heptà i el n-dodecà. Recentment s'han desenvolupat combustibles de substitució multi-components, que s'apliquen tant a estudis experimentals com de modelatge. L'aplicació sistemàtica de combustibles de substitució controlats amb precisió és una via prometedora per a millorar la comprensió de la combustió Dièsel, la seua eficiència, i les seues emissions i proporciona eines per a la recerca de sistemes de combustió nous i alternatius. En aquesta tesi s'han emprat mètodes experimentals i de càlcul per a desenvolupar, estudiar i validar una llibreria de combustibles de substitució multi-components. El primer combustible de substitució es va dissenyar per a reproduir amb precisió les propietats físiques i químiques d'un gasoil amb índex de cetà 50 i un índex de sutge límit (TSI) de 31. El següent pas va ser crear una biblioteca de combustibles de substitució amb 18 combustibles que poden modificar independentment dues propietats clau del combustible: índex de cetà i TSI. En la biblioteca de combustibles l'índex de cetá va oscil·lar entre 35 i 60 amb tres nivells de TSI iguals a 17, 31 i 48 (baix, mitjà i alt rang). Els assajos segons la normativa ASTM van demostrar una bona coincidència amb les propietats del gasoil com a densitat, viscositat, poder calorífic i corbes de destil·lació. Per a comprovar la validesa de la llibreria, es va realitzar un estudi experimental comparatiu sobre el procés de combustió, les emissions gasoses, sutge i partícules d'un gasoil i del seu combustible de substitució ajustat. L'estudi es va realitzar amb un motor monocilíndric Dièsel completament instrumentat i operant amb estratègies de combustió en premescla parcial (PPCI) i de baixa temperatura (LTC), a més de la combustió Dièsel convencional (CDC). Els paràmetres de la combustió com el retard a l'encès i l'alliberament de calor tant de baixa com d'alta temperatura es van aproximar molt bé. Les emissions de gasos, sutge i partícules també van ser similars en variar el nivell d'EGR i la fase de la combustió. La tesi demostra que es poden trobar combustibles de substitució perfectament representatius d'un gasoil corrent, sobre la base de mescles apropiades de n-hexadecà, 2,2,4,4,6,8,8-heptamethylnonà, decahidronaftalé i 1-metilnaftaleno. Així mateix, es conclou que variant la proporció d'aquests quatre components es pot controlar independentment l'índex de cetà i l'índex de sutge límit, alhora que es mantenen les propietats físic-químiques i de combustió del gasoil. La llibreria de combustibles de substitució definida en aquesta tesi és una eina a la disposició dels investigadors per a aprofundir en el coneixement de la combustió Diesel i avançar en el disseny de sistemes futurs de combustió amb millor rendiment i menors emissions. / Szymkowicz, P. (2017). ANALYTICAL AND EXPERIMENTAL INVESTIGATION OF MULTI-COMPONENT SURROGATE DIESEL FUELS [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/90406

Six ã-Al2O3 supported metallic nitride and carbide catalysts were chosen for a scouting test for the production of a diesel fuel cetane enhancer from canola oil. The six catalysts chosen for study were ã-Al2O3 supported molybdenum (Mo) carbide and nitride, tungsten (W) carbide and nitride, and vanadium (V) nitride and carbide. All six catalysts were prepared by the impregnation method and characterized using various techniques. The six catalysts were screened for their affinity for oxygen removal, fatty acid conversion, alkane/olefin selectivity, hydrogen consumption, and gas-by product production from oleic acid. The scouting test was carried out at a reaction temperature of 390°C, a LHSV of 0.46 hr-1, and elevated hydrogen partial pressures of greater than 7000 kPa, in a laboratory microreactor in an upflow configuration. The scouting test revealed that the two molybdenum catalysts performed the best with oxygen removal near 100% and alkane/olefin content of greater than 30%. <p>Next, the supported molybdenum carbide and nitride catalysts were compared against one another over a wider range of operating conditions. A temperature range of 380 390°C, a LHSV range of 0.64 1.28 hr-1, and a hydrogen partial pressure of 7100 kPa were used. Both catalysts had the same metal loading of 7.4 wt% molybdenum. The two catalysts were compared on the basis of oxygen removal, alkane/olefin selectivity, diesel fuel selectivity, and hydrogen consumption, while using both triolein and canola oil as the feed. It was found that the supported molybdenum nitride was the superior choice for this process, specifically when using the more complex canola oil feed. The supported molybdenum nitride catalyst delivered oxygen removal of greater than 85%, alkane/olefin selectivity of greater than 20%, and diesel fuel selectivity of greater than 40%, for all conditions studied. <p>Finally, a preliminary catalyst and process optimization was carried out on the chosen ã-Al2O3 supported molybdenum nitride catalyst. The catalyst optimization consisted of varying the metal loading of the catalyst from 7.4 wt% to 22.7 wt%. The catalysts were examined over a temperature range of 390 410°C, a LHSV range of 0.9 1.2 hr-1, and a hydrogen partial pressure of 8300 kPa, with canola oil as the chosen feed. It was found that the increase in molybdenum loading on the catalyst delivered an average increase in the alkane/olefin selectivity of 43.2% and an average increase in the diesel fuel selectivity of 5.3 %. The process optimization studied a temperature range of 390 410°C, a LHSV range of 0.6 1.2 hr-1, and a hydrogen partial pressure range of 7800 - 8900 kPa, with canola oil as the chosen feed. Within the limits of the design, it was found that the optimum operating conditions were 395°C, 1.05 hr-1, and 8270 kPa. At these conditions the predicted yields of alkane/olefin products and diesel fuel are 47.3 and 50.5 g/100g liquid fed, respectively.

Six ã-Al2O3 supported metallic nitride and carbide catalysts were chosen for a scouting test for the production of a diesel fuel cetane enhancer from canola oil. The six catalysts chosen for study were ã-Al2O3 supported molybdenum (Mo) carbide and nitride, tungsten (W) carbide and nitride, and vanadium (V) nitride and carbide. All six catalysts were prepared by the impregnation method and characterized using various techniques. The six catalysts were screened for their affinity for oxygen removal, fatty acid conversion, alkane/olefin selectivity, hydrogen consumption, and gas-by product production from oleic acid. The scouting test was carried out at a reaction temperature of 390°C, a LHSV of 0.46 hr-1, and elevated hydrogen partial pressures of greater than 7000 kPa, in a laboratory microreactor in an upflow configuration. The scouting test revealed that the two molybdenum catalysts performed the best with oxygen removal near 100% and alkane/olefin content of greater than 30%. <p>Next, the supported molybdenum carbide and nitride catalysts were compared against one another over a wider range of operating conditions. A temperature range of 380 390°C, a LHSV range of 0.64 1.28 hr-1, and a hydrogen partial pressure of 7100 kPa were used. Both catalysts had the same metal loading of 7.4 wt% molybdenum. The two catalysts were compared on the basis of oxygen removal, alkane/olefin selectivity, diesel fuel selectivity, and hydrogen consumption, while using both triolein and canola oil as the feed. It was found that the supported molybdenum nitride was the superior choice for this process, specifically when using the more complex canola oil feed. The supported molybdenum nitride catalyst delivered oxygen removal of greater than 85%, alkane/olefin selectivity of greater than 20%, and diesel fuel selectivity of greater than 40%, for all conditions studied. <p>Finally, a preliminary catalyst and process optimization was carried out on the chosen ã-Al2O3 supported molybdenum nitride catalyst. The catalyst optimization consisted of varying the metal loading of the catalyst from 7.4 wt% to 22.7 wt%. The catalysts were examined over a temperature range of 390 410°C, a LHSV range of 0.9 1.2 hr-1, and a hydrogen partial pressure of 8300 kPa, with canola oil as the chosen feed. It was found that the increase in molybdenum loading on the catalyst delivered an average increase in the alkane/olefin selectivity of 43.2% and an average increase in the diesel fuel selectivity of 5.3 %. The process optimization studied a temperature range of 390 410°C, a LHSV range of 0.6 1.2 hr-1, and a hydrogen partial pressure range of 7800 - 8900 kPa, with canola oil as the chosen feed. Within the limits of the design, it was found that the optimum operating conditions were 395°C, 1.05 hr-1, and 8270 kPa. At these conditions the predicted yields of alkane/olefin products and diesel fuel are 47.3 and 50.5 g/100g liquid fed, respectively.

This research work characterises diesel engine soot physiochemical properties and engine performance and emissions for the combustion of two common mineral diesel fuels (low and medium sulphur) and a RME B100 biodiesel fuel at two geometric compression ratios (19.5:1 and 16.5:1) and a broad range of EGR (10 to 55%) for an otherwise unmodified VW 1.9TDI 130PS engine. The principal focus of the research is the physiochemical characterisation of soot sampled from the engine exhaust manifold and also a DPF in the exhaust and exploring how the fuel type, compression ratio and EGR influence the soot properties and how these properties then influence the evolution of the soot in the exhaust.

Orientadores: Antonio Carlos Bannwart, Edvaldo Sabadini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica e Instituto de Geociências / Made available in DSpace on 2018-08-18T05:50:39Z (GMT). No. of bitstreams: 1 Destefani_ThaisCristina_M.pdf: 2402197 bytes, checksum: 41c2a60d04751d025a08cd311d99302a (MD5) Previous issue date: 2011 / Resumo: A redução de atrito hidrodinâmico tem importantes aplicações em engenharia de petróleo, propiciando a produção e o transporte de petróleo ou seus derivados a vazões mais altas. As dimensões continentais do território brasileiro implicam na necessidade de uma eficiente rede de distribuição de derivados de petróleo, como por exemplo, o óleo diesel. O presente trabalho visa investigar o desempenho de dois agentes redutores de atrito (ARA's) comerciais que, injetado em ínfimas proporções (da ordem de ppm) em uma tubulação de escoamento de diesel, podem causar significativa diminuição em sua tensão de cisalhamento turbulenta, reduzindo a queda de pressão por atrito durante seu escoamento no interior de um tubo. Em uma primeira fase, as amostras com e sem ARA foram testadas em um reômetro, utilizando uma cela tipo Couette, avaliando a proporção do torque aplicado no diesel puro e no diesel com ARA, a uma mesma velocidade angular. Com uma concentração de 7 ppm foi observada uma redução de atrito da ordem de 13% e 18% para cada um dos aditivos. A avaliação da redução do atrito em tubulação consiste na comparação do diferencial de pressão obtido para escoamento de diesel com e sem ARA em um trecho de tubo. Estes experimentos mostram uma redução de atrito de 48% e 58% na injeção de 50 ppm de cada um dos aditivos estudados. Apesar dos experimentos em reômetro terem maior rapidez, controle de variáveis e menor consumo de materiais, o escoamento no interior da cela Couette é diferente em relação ao escoamento em tubulações. No entanto, os testes em tubulações são mais próximos das demandas reais, sendo assim importantes para o entendimento do fenômeno / Abstract: The drag reduction has important applications in petroleum engineering, allowing production and transportation of oil and derivatives at higher flow rates. The continental dimensions of Brazil implies the necessity for an efficient distribution network for oil products, such as diesel. This study aims to investigate the performance of two commercial drag reduction agents (DRA's), injected in very small proportions (the order of ppm) in a diesel fuel pipe flow. This injection may induce significant decrease in the turbulent shear stress, reducing the pressure drop by friction during the flow inside a tube. In a first step, samples with and without DRA were tested in a rheometer using a Couette cell type. The ratio of torque applied in pure diesel and diesel with DRA were analyzed at the same angular velocity. Using 7 ppm of concentration for both DRA, it was observed drag reduction of the order of 13% and 18% for each additives. The analysis of drag reduction in pipe flow involves the ratio of pressure differential by the flow of diesel with and without DRA in a section of tube. These tests show a drag reduction of 48% and 58% with 50 ppm for each DRA studied. Despite the rheometer experiments offer greater speed, control variables and lower consumption of materials, the flow inside the Couette cell is different compared with flow pipes. However, tests on pipes are closer to real demands therefore important for understanding the drag reduction phenomenon. With these experimental data, it is expected to determine correlations between tests in pipeline and rheometer, estimating the turbulence effect in these two systems / Mestrado / Explotação / Mestre em Ciências e Engenharia de Petróleo

Orientador: Celio Pasquini / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-06T15:50:13Z (GMT). No. of bitstreams: 1 Lauro_MauroJose_M.pdf: 608309 bytes, checksum: 2021b49ff67c5dac4eda1d87cf0490de (MD5) Previous issue date: 2006 / Resumo: O objetivo principal deste trabalho foi avaliar a incorporação de fibras curtas de sílica (FS) e da borracha etileno-propileno-dieno funcionalizada com anidrido maleico (EPDM-g-AM) em polimérica de poliamida 6 (PA 6). A fibra utilizada como carga é um produto natural constituído de sílica amorfa proveniente da fossilização de animais multicelulares. Com a finalidade de promover a melhor adesão interfacial entre a fibra e a matriz polimérica, as fibras foram modificadas com aminopropiltrietoxissilano (APTS), um agente de acoplamento. Os materiais foram preparados em extrusoras monorosca e duplarosca e, submetidos a ensaios mecânicos de tração, flexão e de impacto Izod. Foram também avaliadas as características térmicas e morfológicas desses materiais. As fibras de sílica não alteraram a estabilidade térmica da PA 6 e apresentaram eficiência de reforço, dentro do intervalo de composição estudado; entretanto, o alongamento na ruptura foi comprometido. A resistência ao impacto do polímero não variou significativamente com a incorporação de FS. Por outro lado, o tipo de extrusora utilizada para processamento alterou a cristalinidade da PA 6 e, conseqüentemente, as propriedades mecânicas nos compósitos binários de PA 6/FS. A modificação da superfície da fibra com APTS não foi adequada para melhorar as propriedades mecânicas, no entanto, a análise da microestrutura dos compósitos obtidos indicou adesão entre as fases. Em relação às blendas de PA 6/EPDM-g-AM, o tamanho médio de partícula da fase dispersa promoveu um efeito de tenacificação da PA 6. Os compósitos ternários de PA 6 contendo 20% de EPDM-g-AM e proporções diferentes de FS (5 a 20%) apresentaram redução na resistência ao impacto quando pequenas quantidades de FS foram adicionadas. Apesar da redução no valor desta propriedade, os compósitos obtidos exibiram boa tenacidade. Desta forma, a combinação de fibras curtas de sílica e borracha de EPDM-g-AM em poliamida 6 permitiu recuperar parcialmente a rigidez e a resistência ao impacto, que são comprometidas quando esses aditivos são utilizados separadamente / Abstract: The main goal of this work was to evaluate the incorporation of short silica fibers (SF) and ethylene-propylene-diene rubber, functionalized with maleic anhydride (EPDM-g-MA), in a polyamide 6 (PA 6) matrix. The fiber used as filler is a natural product made up of amorphous silica from the fossilization of multicelular animals. In order to promote a better interfacial adhesion between the fiber and the polymeric matrix, fibers were modified with the aminopropyltriethoxysilane (APTS) coupling agent. The materials were prepared in single and twin-screw extruders for tensile, flexural and Izod impact mechanical tests. The mechanical, morphological and thermal properties of these materials were evaluated. Silica fibers did not change the thermal stability of the polymer and presented efficiency for reinforcement. However, the elongation at break was impaired. The impact strength of the polymer did not change significantly with the SF content. On the other hand, the type of extruder used for processing changed the mechanical properties and the crystallinity of PA 6 in the PA 6/SF binary composites. The fiber surface modification with APTS was not effective, as verified by the decrease of the mechanical properties. The morphology of composites showed adhesion between the phases. Taking into account the PA 6/EPDM-g-MA blends, the average size of dispersed phase, associated to impact strength in the 20% EPDM-g-MA composition promoted a toughening effect of the blends. Ternary PA 6 composites containing 20% EPDM-g-MA and different SF amounts (5-20%) presented tendency towards the reduction of the impact strength when small SF amounts were added. In spite of the reduction in the value of this mechanical property, the composites obtained exhibited good toughness. Thus, combining short silica fibers and EPDM-g-MA rubber with polyamide 6, the stiffness and the impact strength, that are impaired when these additives are separately used, were partially recovered. / Mestrado / Quimica Analitica / Mestre em Química

Energy carriers, such as coal, natural gas and biomass, can be converted by Fischer-Tropsch technology into synthetic crude (syncrude). Fischer-Tropsch derived syncrude can then be refined to transportation fuels, such as motor-gasoline, jet fuel and diesel fuel. These fuels meet the same specifications as crude oil derived transportation fuels. Conventional refining technologies have to be adapted to deal with Fischer-Tropsch syncrudes, because they differ significantly from crude oil with respect to composition. Some of the key differences are the high concentration of oxygenates and olefins and absence of sulphur in Fischer-Tropsch syncrude. Imposing a crude oil refining methodology on syncrude can lead to unwieldy and expensive refineries. Yet, despite an abundance of literature of Fischer-Tropsch synthesis, there is little literature that deals with the refining of Fischer-Tropsch syncrude. The present study investigated current refining practice for both crude oil and Fischer-Tropsch syncrude in order to identify fundamental differences in their refining focus and conversion behaviour. This was followed by a critical evaluation of the compatibility of syncrudes from high temperature Fischer-Tropsch (HTFT) and low temperature Fischer-Tropsch (LTFT) synthesis with the chemistry and catalysis of various conversion processes. The conversion processes that were evaluated include isomerisation, oligomerisation, etherification, alkylation, metathesis, hydrogenation, hydroisomerisation, hydrocracking, catalytic cracking, coking, thermal cracking, catalytic reforming and dehydration. The recommendations from the technology evaluation provided the foundation for the development of Fischer-Tropsch syncrude based refinery designs. Refinery designs were developed to determine configurations that would maximise the production of on-specification motor-gasoline, jet fuel and diesel fuel respectively. It could be shown that less complex refinery designs were required to refine Fischer-Tropsch syncrude to motor-gasoline and jet fuel, than were required for crude oil refining. It was also shown that on a molecular level Fischer-Tropsch syncrude is unsuited for maximising the production of Euro-4 type diesel fuel. The present study illustrates the advantage of considering fundamentals in developing refineries specifically for Fischer-Tropsch syncrude, rather than imposing crude oil design practises on Fischer-Tropsch syncrude refinery designs. / Thesis (PhD (Chemical Engineering))--University of Pretoria, 2008. / Chemical Engineering / unrestricted

The fate of nanoparticulate cerium oxide from the diesel fuel catalyst Envirox was studied from its presence in the additive to its transformations during combustion through its exposure to plants and soils using a broad range of analytical techniques. Envirox is a fuel-borne catalyst comprised of nanoparticles of cerium oxide suspended in kerosene. The particles suspended in Envirox were confirmed by synchrotron X-ray diffraction, dynamic light scattering, and electron microscopy to be 5-7 nm crystals of CeO2 present as 15 nm aggregates. Significant changes to the particles were induced by the combustion process, resulting in 50-300 nm euhedral crystals of CeO2 in the exhaust as discovered using high resolution transmission electron microscopy. Single particle electron diffraction of the emitted cerium oxide particles showed evidence of ordered oxygen vacancies, indicative of a superstructure. Variations in the engine operating load resulted in no significant differences in the emitted cerium oxide particles. The mobility through soils and impacts on the plant Brassica napus (dwarf essex rape) of the emitted cerium oxide were compared to small and large CeO2 nanoparticles as well as diesel particulate matter emissions with very low cerium. The small CeO2 nanoparticles exhibited high mobility through soils and significant uptake and translocation in the plants. The large CeO2 nanoparticles showed extremely low mobility in soils and no significant increase in cerium anywhere in the plants. Cerium emissions from a diesel engine utilizing Envirox was found to have moderate mobility through the soils as well as an increased association with the roots of the plants, though translocation of the cerium into the aboveground biomass was not statistically significant. Despite uptake and translocation of some materials by B. napus, exposure to these cerium sources at 100 ppm Ce in the topsoil showed no significant impacts on the growth or overall health of the plants when compared to unexposed control samples. This dissertation shows that CeO2 nanoparticles employed as catalysts suspended in diesel fuel are altered during their use resulting in changes to their mobility and interaction upon entering the environment. This dissertation lays the groundwork for a new approach to nanotoxicology. / Ph. D. / Understanding the environmental impacts – and subsequently the impacts on mankind – of the use of nanomaterials is an enormously complex problem. The bottomup approach, whereby one can predict impacts from fundamental principals, is not practical because nanotechnology implementation into products is occurring far too rapidly and it is impossible for environmental toxicologists to keep pace. The properties of a nanomaterial are controlled by small changes to its physical/chemical properties that can be tuned to suit many different practical applications. During their use and subsequent release into the natural environment, nanomaterials are exposed to incredibly complex spaces that are capable of modifying the original nanomaterial still further. Thus, the originally produced nanomaterial will continue to evolve, and therefore change in its interaction with biotic and abiotic systems. In this dissertation, we examine the use of nanoparticulate cerium oxide in fuelborne catalysts as a case study. As a fuel-borne catalyst, nanoparticulate cerium oxide is employed to reduce carbon dioxide (a greenhouse gas and contributor to global climate change) and particulate matter (a known carcinogen) emissions from combustion in a diesel engine. Fuel-borne catalysts achieve this through the suspension of cerium oxide nanoparticles in the fuel, which go through the combustion process and exit the tailpipe with the rest of the diesel exhaust. Concerns over the emission of this emerging contaminant have resulted in its limited market penetration. Here we show that the nanoparticulate cerium oxide in fuel-borne catalysts is substantially altered by the combustion process and is emitted as significantly larger particles in the exhaust. We suspected that the emitted cerium oxide would have different behavior in the environment from previously studied, laboratory synthesized cerium oxide nanoparticles. The behavior of emitted cerium oxide was compared with that of laboratory synthesized cerium oxide nanoparticles by exposure to the plant Brassica napus. The exposure experiments showed that cerium oxide emitted from the combustion of a fuel-borne catalyst did indeed behave differently in the environment, though none of the exposures proved toxic to the plants at the realistic concentrations utilized in the study.

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