This study investigated the adsorptive and desorption capacity of HgCl2 onto powdered activated carbon derived from carbon black of pyrolyzed waste tires (CPBAC) via thermogravimetric analysis (TGA). Due to incomplete classification and recycling of municipal solid wastes (MSW), they still mix with a lot of hazardous materials, which unfortunately can not be removed by incinerators and air pollution control devices(APCDs). Among them, mercury and its pollutants attract more attention by people. Mercury and its pollutants emitted from the incineration of municipal solid wastes could cause severely adverse effects on human health and ecosystem since they exist mainly in vapor phase due to high vapor pressure. If they can not be remove by the air pollution control devices, they will be emitted to the atmosphere and cause serious effects on environmental ecology via various routes. Activated carbon has been widely applied to the treatment of organic compounds and heavy metals in wastewater and waste gas stream. However, the adsorptive capacity of activated carbon decreases with adsorption temperature. The low adsorptive capacity of activated carbon at high temperature (>150 oC) can be overcome by impregnated activated carbons. Previous study reported that sulfur impregnated powdered activated carbons could effectively remove the vapor-phase elemental mercury (Hgo) emitted from MSW incinerators and utility power plants. However, the impregnated typically used is sulfur (S) which is solely applied for the adsorption of elemental mercury (Hgo). Besides, these studies seldom investigate the distribution of impregnated sulfur in the inner pores of activated carbon and its effects on the specific surface area and pore size distribution. Thus, this study was to investigate the fundamental mechanisms for the adsorption/desorption of HgCl2 by/from sulfur impregnated PAC. Experimental results indicated that the sulfur content of sulfur impregnated CBPAC decreased with increasing impregnation temperatures form 400 to 650 oC; while the surface area of sulfur impregnated CBPAC increased with impregnation temperatures. In this study, TGA was applied to obtain the adsorptive capacity of HgCl2 onto CBPAC with adsorption temperature (150oC) and influent HgCl2 concentration (100~500 £gg/m3). Experimental results indicated that the adsorptive capacity of CBPAC increased with the increase of influent HgCl2 concentration and surface area of the activated carbon. This study revealed that the impregnation of sulfur on CBPAC could increase its adsorption capacity at high temperatures. Desorption experimental parameters included desorption temperature (400, 500, and 600 oC), heating rate (10, 15, and 20 oC /min) and regeneration cycle (1~7 cycles). In probing into the regeneration efficiency of CBPAC, experiments were conducted at the desorption times of 60 and 30 min. The results suggested the regeneration efficiency of carbon under 30 min was generally highter than that under 60 min. Because the desorption time was more longer and the sulfur content was lesser. Therefore, the regeneration times was reduce. Experimental results indicated that the mechanism of HgCl2 desorption from the spent CPBAC was strongly affected by desorption temperature. Both the desorption efficiency and the desorption rate of HgCl2 increased dramatically with desorption temperature. The desorption heat of HgCl2 (823 KJ/mole) was much higher than the vaporization heat of HgCl2 (59.2 KJ/mole), indicating that the adsorption of HgCl2 on sulfur impregnated CBPAC was chemical adsorption. Consequently, raising desorption temperature could enhance the desorption of HgCl2 and shorten the duration for HgCl2 desorption. Moreover, the formation of HgS during the desorption of HgCl2 from activated carbons can be proved by the surface characteristics of sulfur impregnated activated carbons. Results obtained from the regeneration of sulfur impregnated activated carbons indicated that the regeneration cycles decreased as the desorption duration increased. It was attributed to the potential desorption of sulfur from actived carbons, which thus decreased the adsorptive capacity and the regeneration cycles.

No description available.

Då ett eventuellt förbud av nya kreosotimpregnerade stolpar kan bli en verklighet inom EU år 2018 letar Vattenfall efter andra alternativ. Stål, betong, limträ och komposit anses idag vara de mest konkurrenskraftiga alternativen och kommer att undersökas i denna rapport. Grundläggande tekniska egenskaper, miljöutsläpp och kostnader för de olika stolptyperna kommer att analyseras i rapporten och jämföras mot den kreosotimpregnerade furustolpen. Rapporten beskriver hur de olika stolpalternativen lämpar sig i Vattenfalls elnät i Sverige. P.g.a. sekretesskäl kommer exakta prisuppgifter inte att redovisas. Prisuppgifterna för inköp och återvinning kommer istället att redovisas som en kvot mellan den alternativa stolpen dividerat kreosotstolpen. Inte heller kommer slipers och andra fundament att behandlas i rapporten. Metoden som används bygger på att först presentera relevant teori kring vardera stolptyp. Även impregneringsprocessen, besiktningsmetoder och nedbrytning/återvinning av stolpar redogörs i rapporten. Den miljömässiga analysen bygger på IVL Svenska Miljöinstitutets LCA-analys där kreosotstolpen jämförs med andra stolptyper. Det visar sig dock att kreosotstolpen är den stolptyp som bidrar till minst miljöutsläpp om man ser till hela dess livscykel. Slutsatsen är att kompositstolpen visar sig vara ett av de mest konkurrenskraftiga alternativen då den ses som ett miljövänligt alternativ och dess vikt gör den lätt att hantera. Den är heller inte impregnerad och kan därför monteras överallt utan några rättsliga restriktioner. Denna stolptyp är också väldigt aktuell då den i dagsläget är väl etablerad på marknaden. / Because of a possible ban of creosote impregnated poles can become a real scenario within the EU the year 2018 Vattenfall are searching for other alternatives. Steel, concrete, laminated wood and composite are considered the most competitive alternatives today and are being investigated in this report. Basic technical specifications, impacts on the environment and costs of the different pole types are being analyzed in the report and compared to the creosote impregnated pine pole. This report will describe how well the alternative pole types are suited in Vattenfalls electrical grid in Sweden. Due to confidentiality reasons the exact amount of costs and expenses will not be included in the report. The price of purchase and recycling will instead be presented as a quota between the alternative pole divided by the creosote pole. Neither will sleepers nor other pole foundations be included in this report. The method that is being used is to first present relevant theory about the mentioned pole types. Also the impregnation process, survey and disintegration/recycling of poles will be explained. The environmental analysis are based on IVL Svenska Miljöinstitutet's LCA where the creosote pole are compared to its alternatives. They conclude that it is the creosote pole that has the least impact on the environment if you look at the whole life-cycle. The conclusion is that the composite pole are shown to be one of the most competitive alternatives because it is considered to be environmental-friendly and its low weight makes it easy to work with. Also, it's not impregnated and can therefore be used everywhere without any legal restrictions. This pole type is also very relevant as it is already released on the market.

This experimental study focuses on the links that exist between the mechanical pull-out behaviour of multi-filament yarns embedded in concrete and the impregnation of the yarn by the concrete. To this aim, 5 glass yarns have been embedded in concrete (AR and E glass yarns from assembled or direct roving). A pre-treatment was applied to the yarn before the casting, and was chosen in the following three: wetting, drying or pre-impregnation with a cement slurry. By this way, 15 yarn / pre-treatment combinations were obtained that generate 15 conditions of impregnation of the yarn by the cementitious matrix. In each case, the mechanical properties were determined from a classical pull-out test and the yarns impregnation properties were characterized by two dedicated tests: yarns porosity measurements and along yarn water flow measurements. By studying the relationship between the mechanical behaviour and the physical properties of the impregnated yarns, it is shown that the pre- and post-peak behaviour are mainly connected to the flow rate measured during the water flow measurements, which suggest a specific influence of the connected pores parallel to the filaments and of the penetration depth of the matrix into the yarn. The postpeak and the residual behaviour are moreover linked to the yarn pore volume associated to the disorder induced in the filaments assembly by the penetration of the matrix. The overall result of this work is a contribution to the understanding of the relationship between the impregnation of the yarns and the pull-out behaviour.

Made available in DSpace on 2015-05-08T15:00:04Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2562395 bytes, checksum: f0b5df1ebe5874b77596b4881477b494 (MD5) Previous issue date: 2010-09-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The interest of the use of Bamboo in the field of construction is growing around the world. This can be attributable to its good engineering properties as well as the fact that it comes from a renewable source. In the North-eastern, Bambusa vulgaris is the most common type. The aim of the research is to evaluate the parameters of impregnation of the bamboo with diverse fluids aiming at to the improvement of the mechanical properties and durability. In this way, it was necessary to evaluate the microstructure of the bamboo, so that the possibility of impregnation of these fluids can be observed. Some treatments of sample preparation had been tested for one better characterization of the porous structure of the bamboo through optic microscopy, having been chosen the attack for a FAA solution (4% of formaldehyde, 5% of acetic acid ascetic, 50% of ethylic alcohol). The constituents of the bamboo (parenchyma, fibers and vases) has been quantified and analyzed through a tool of recognition of images of optic microscopy. Of general form the mature bamboo presented 51.45% of parenchyma, 38.75% of fibres and 9.73% of vases. Already the young presented 57.64% of parenchyma, 33.55% of fibres and 8.81% of vases. The absorption of the culms was also evaluated by means of change in mass with time. The bamboo absorption capacity was assessed for different fluids along the time. The order of magnitude of the absorption is of 5 the 10%, independently of the used fluid. The absorption of the bamboo varied with the specific mass and viscosity of fluids. The pH of the young and a mature bamboo was determined, varying enters 5,72 the 6,61. Two machine of fluid impregnation was projected based in the Boucherie method, one for resin and to another one for the other fluid. Some parameters in the process of fluid impregnation had been studied in the bamboo, that is the following ones: viscosity and density of the fluid (distilled water, oil 20W and oil 40W), pressure of impregnation, time of harvesting of the bamboo (immediatly after harvesting and 7 days after harvesting), type of drying (greenhouse 50oC and to the outdoors) and geometric properties of the bamboo (initial and final mass, initial and final specific mass, volum, external, internal diameter and thickness of the wall). The variable of reply of the impregnation assay had been: time of fist drop, outflow and time to cross 20 g of fluid. An analysis was made statistics, where if it observed which independent variable had influenced significantly in the reply variable. It was observed that it is possible to impregnate fluid of diverse viscosities, mainly had the porous structure of the bamboo that is around 10%. The use of the machine if showed beneficial for this the process, therefore the pressure introduction also provoked a fast impregnation and a good development of flow. After the evaluation of the microstructural parameters and impregnation, the bamboos had been impregnated with a resin and evaluated some mechanical properties. The bamboos impregnated with resin had a bigger compressive strength, modulus of elasticity and a bigger durability of what the bamboos without treatment. / O interesse pela utilização de bambu na área da construção está crescendo em todo o mundo. Isto pode ser atribuído às suas boas propriedades de engenharia, bem como o fato de se tratar de uma fonte renovável. Na região Nordeste, o Bambusa vulgaris é a espécie mais comum. O objetivo da pesquisa é avaliar os parâmetros de impregnação do bambu com diversos fluidos visando à melhoria das propriedades mecânicas e durabilidade. Desta forma, foi necessário avaliar a microestrutura do bambu, para que pudesse ser observada a possibilidade de impregnação desses fluidos.Vários tratamentos de preparação das amostras foram testados para uma melhor caracterização da estrutura porosa do bambu através de microscopia ótica, tendo sido escolhido o ataque por uma solução de FAA (4 % de formaldeído, 5 % de ácido acético, 50 % de álcool etílico). Os tecidos do bambu (parênquima, fibras e vasos) foram quantificados e analisados através de uma ferramenta de reconhecimento de imagens de microscopia ótica. De forma geral o bambu maduro apresentou 51,45 % de parênquima, 38,75 % de fibras e 9,73 % de vasos. Já o verde apresentou 57,64 % de parênquima, 33,55 % de fibras e 8,81 % de vasos. A absorção dos colmos também foi avaliada por meio da variação da massa com o tempo. A capacidade de absorção de bambu foi avaliada para diferentes fluidos, ao longo do tempo. A ordem de grandeza da absorção é de 5 % a 10 %, independentemente do fluido utilizado. A absorção do bambu variou com a massa específica e viscosidade dos fluidos. O pH dos colmos verdes e maduros foi determinado, variando entre 5,72 a 6,61. Foram projetadas duas máquinas de impregnação de fluidos baseadas no método Boucherie, uma para resina e a outra para os demais fluidos. Foram estudados vários parâmetros no processo de impregnação de fluidos no bambu, que são os seguintes: viscosidade e massa específica do fluido (água destilada, óleo 20 W e óleo 40 W), pressão de impregnação, tempo de corte do bambu (recém-cortado e após 7 dias de corte), tipo de secagem (estufa a 50oC e ao ar livre) e as propriedades geométricas do bambu (massa inicial e final, massa específica inicial e final, volume, diâmetro externo, interno e espessura da parede). As variáveis de resposta do ensaio de impregnação foram: tempo da 1ª gota e tempo para atravessar 20 g de fluido. Foi feita uma análise estatística, em que se observaram quais variáveis independentes influenciaram significativamente nas variáveis de resposta. Observou-se que é possível impregnar fluidos de diversas viscosidades, devido principalmente a estrutura porosa do bambu que é em torno de 10%. A utilização da máquina se mostrou benéfica para este processo, pois a introdução de pressão provocou uma rápida impregnação e também um bom desenvolvimento de fluxo. Após a avaliação dos parâmetros microestruturais e de impregnação, os bambus foram impregnados com uma resina e foram avaliadas algumas propriedades mecânicas. Os bambus impregnados com resina tiveram uma maior resistência à compressão, módulo de elasticidade e uma maior durabilidade do que os bambus in natura.

Orientador: Antonio José Gomez Cobo / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-25T04:45:50Z (GMT). No. of bitstreams: 1 Ganzaroli_DaianaRezende_M.pdf: 2594677 bytes, checksum: 083b3d18fb22abe80176433b885c8c2a (MD5) Previous issue date: 2014 / Resumo: A hidrogenação de compostos aromáticos tem sido muito estudada devido à sua ampla gama de aplicações industriais, bem como às restrições ambientais impostas por diversos países. Nesse contexto, o presente trabalho tem o objetivo estudar os efeitos do pH de impregnação e da natureza do agente redutor sobre o desempenho de catalisadores de Ni e Ru suportados em ?-Al2O3, empregados na hidrogenação de tolueno em fase líquida. Para tanto, catalisadores foram preparados a partir de soluções aquosas dos precursores de NiCl3.6H2O e RuCl3.xH2O, através de impregnação úmida conduzida a pH constante entre 4 e 8. Durante a impregnação, catalisadores foram reduzidos a 353 K (80 ºC) em fase líquida, empregando-se formaldeído (H2CO) ou boroidreto de sódio (NaBH4) como agentes redutores. Os catalisadores de Ni e Ru também foram reduzidos sob fluxo de H2 a 773 e 573 K (500 e 300 ºC) respectivamente, após a impregnação úmida. O suporte foi caracterizado utilizando as técnicas de análise granulométrica, adsorção de N2 (método de B.E.T.) e titulação potenciométrica. As técnicas de MEV+EDX e XPS foram empregadas para determinar a composição química dos sólidos empregados, e a formação da fase ativa dos catalisadores foi estudada através de TPR. O desempenho dos catalisadores foi avaliado na reação de hidrogenação do tolueno em fase líquida, conduzida num reator Parr do tipo "slurry" à temperatura de 373 K (100 ºC) e sob pressão de H2 de 5 MPa (50 atm). Os resultados obtidos mostram que os catalisadores de Ru/Al2O3 são muito mais ativos que os catalisadores de Ni/Al2O3, sendo ainda seletivos para a obtenção do produto da hidrogenação parcial do tolueno (metilcicloexeno). A maior atividade dentre os catalisadores de Ni/Al2O3 é obtida para um pH de impregnação acima do ponto isoelétrico (pI) do suporte, igual a 6,2, utilizando-se o agente redutor H2CO. No caso dos catalisadores de Ru/Al2O3, o agente H2CO também leva às maiores atividades catalíticas, tendo-se o valor máximo para o pH igual ao pI do suporte. Já o maior rendimento de metilcicloexeno é obtido para o pH igual a 4. Os comportamentos catalíticos observados são analisados e discutidos à luz dos resultados da caracterização dos sólidos e da literatura técnica especializada / Abstract: The hydrogenation of aromatic compounds has been studied due to the wide range of industrial applications, as well as to environmental restrictions imposed by several countries. In this context, the present work aims to study the effects of the impregnation pH and the nature of the reducing agent on the performance of Ni and Ru catalysts supported on ?-Al2O3, employed for toluene hydrogenation in liquid phase. For this, catalysts were prepared from aqueous solution of NiCl3.6H2O and RuCl3.xH2O precursors by wet impregnation, conduced at constant pH between 4 and 8. During impregnation, catalysts were reduced at 353 K (80 ºC) in liquid phase, using formaldehyde (H2CO) or sodium borohydride (NaBH4) as reducing agents. The Ni and Ru catalysts were also reduced under H2 flow at 773 and 573 K (500 and 300 °C) respectively, after the wet impregnation. The support was characterized using the techniques of particle size, N2 adsorption (B.E.T. method) and potentiometric titration. The techniques of SEM+EDX and XPS were used to determine the chemical composition of the employed solids, and the formation of the catalysts active phase was studied by TPR. The catalysts performance were evaluated for toluene hydrogenation reaction in the liquid phase, carried out in a Parr reactor of the slurry type at the temperature of 373 K (100 ° C) and under H2 pressure of 5 MPa (50 atm). The results show that Ru/Al2O3 catalysts are much more active than the Ni/Al2O3 catalysts, and even selective for obtaining the product of the partial hydrogenation of toluene (methylcyclohexene). The highest activity among the Ni/Al2O3 catalysts is obtained by impregnation at pH above of the isoelectric point (pI) of the support, equal to 6.2, using the reducing agent H2CO. In the case of the Ru/Al2O3 catalysts, the H2CO agent also leads to higher catalytic activities, having a maximum value at pH equal to the support pI. However, the highest yield of methylcyclohexene is obtained at pH 4. The observed catalytic behaviors are analyzed and discussed in the light of the results of the characterization of solids and specialized technical literature / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestra em Engenharia Química

A vehicle flying at hypersonic speeds, i.e. at speeds greater than Mach 4, needs to be able to withstand the heat arising from friction and shock waves, which can reach temperatures of up to 3000oC. The current project focuses on producing thermal protection systems based on ultra high temperature ceramic (UHTC) impregnated carbon-carbon composites. The carbon fibres offer low mass and excellent resistance to thermal shock; their vulnerability is to oxidation above 500oC. The aim of introducing HfB2, a UHTC, as a coating on the fibre tows or as particulate reinforcement into the carbon fibre preform, was to improve this property. The objectives of this project were to: i) identify a low temperature synthesis route for group IV diborides, ii) produce a powder fine enough to reduce the difficulties associated with sintering the refractory diborides, iii) develop sol-gel coating of HfB2 onto carbon fibre tows iv) improve the solid loading of the particulate reinforcement into the carbon fibre preform, which should, in turn, increase the oxidation protection. In order to achieve the above set objectives, fine HfB2 powder was synthesized through a low temperature sol gel and boro/carbothermal reduction process, using a range of different carbon sources. Study of the formation mechanism of HfB2 revealed an intermediate boron sub-oxide and/or active boron formation that yielded HfB2 formation at 1300oC. At higher temperatures the formation of HfB2 could be via intermediate HfC formation and/or B4C formation. Growth mechanism analysis showed that the nucleated particles possessed screw dislocations which indicated that the formation of HfB2 was not only through a substitution reaction, but there could have been an element of a precipitation nucleation mechanism that lead to anisotropic growth under certain conditions. The effect of carbon sources during the boro/carbothermal reduction reaction on the size of the final HfB2 powders was analysed and it was found that a direct relation existed between the size and level of agglomeration of the carbon sources and the resulting HfB2 powders. A powder phenolic resin source led to the finest powder, with particle sizes in the range 30 to 150 nm. SPS sintering of the powder revealed that 99% theoretical density could be achieved without the need for sintering aids at 2200oC. Sol-gel coatings and slurry impregnation of HfB2 on carbon fibres tows was performed using dip coating and a 'squeeze-tube' method respectively. Crack free coatings and non-porous matrix infiltration were successfully achieved. The solid loading of the fine HfB2 into the carbon fibre preform was carried out through impregnation of a HfB2 / phenolic resin/acetone slurry using vacuum impregnation. Although the sub-micron Loughborough (LU) powders were expected to improve the solid loading, compared to the commercially available micron sized powders, due to the slurry made from them having a higher viscosity because of the fine particle size, the solids loading achieved was consequently decreased. Optimisation of the rheology of the slurry with LU HfB2 still requires more work. A comparison of the oxidation and ablation resistance of the Cf-HfB2 composites prepared with both commercial micron sized HfB2 powder and Loughborough sub-micron sized HfB2 powder, each with similar level of solid loading, was carried out using oxyacetylene torch testing. It was found that the composite containing the finer, Loughborough powders suffered a larger erosion volume than the composite with the coarser commercial powders indicating that the former offered worse ablation and oxidation resistance than the latter. A full investigation of the effect of solids loading and particle size, including the option of using mixtures of fine and coarse powders, is still required.

Orientador: Antonio José Gomez Cobo / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T13:34:13Z (GMT). No. of bitstreams: 1 Suppino_RaphaelSoeiro_D.pdf: 5206972 bytes, checksum: 371cc5a8b519d6d7c42de22340b60b7f (MD5) Previous issue date: 2014 / Resumo: A hidrogenação de compostos aromáticos é uma reação química de grande interesse industrial. Diante das crescentes restrições à presença desses compostos em combustíveis, a hidrodesaromatização catalítica é um dos processos mais importantes nas refinarias. Nesse contexto, o presente trabalho tem por objetivo estudar a hidrogenação de compostos aromáticos em fase líquida, empregando catalisadores à base de metais básicos (Fe, Co, Ni) e nobres (Ru, Pd, Pt) suportados em Al2O3 via impregnação úmida. Especificamente, buscou-se avaliar a influência da composição química, da redução sob H2 e do reuso de tais catalisadores sobre o desempenho catalítico. Catalisadores mono e bimetálicos foram preparados a partir de precursores clorados, através de coimpregnação úmida conduzida a 353 K (80 oC) e pH igual a 10. Durante a impregnação úmida, os sólidos foram reduzidos em fase líquida com formaldeído, sendo posteriormente reduzidos ex situ ou in situ sob H2. Os sólidos preparados foram caracterizados através das técnicas de titulação potenciométrica, adsorção de N2, espectroscopia de fotoelétrons excitados por raios X, microscopia eletrônica (varredura e transmissão) e redução à temperatura programada. O desempenho dos catalisadores foi avaliado na hidrogenação do tolueno e de uma mistura de aromáticos. As reações foram realizadas num reator Parr do tipo slurry, sob pressão de H2 de 5 MPa (50 atm) e à temperatura de 373 K (100 oC), com a adição de água e de solventes ao meio reacional. Na hidrogenação do tolueno, os catalisadores à base de Ru são muito mais ativos e seletivos ao produto da hidrogenação parcial (metilcicloexeno). O efeito da redução sob H2 sobre a atividade catalítica se mostra dependente da natureza do metal básico, enquanto os catalisadores à base de metais nobres têm a atividade diminuída. A adição de metal básico ao catalisador de Ru/Al2O3 também leva a uma diminuição da atividade, mas um efeito sinergético é obtido com a associação Ru-Pt. Para a mistura de aromáticos, a taxa de hidrogenação com o catalisador de Ru-Pt/Al2O3 segue a ordem: benzeno > tolueno > o-xileno > p-xileno. Nesse caso, a adição de solventes ao meio reacional e o reuso do catalisador diminuem a taxa de hidrogenação do benzeno e do tolueno, favorecendo a hidrogenação dos xilenos / Abstract: The hydrogenation of aromatic compounds is a chemical reaction of major industrial interest. Given the increasing restrictions on the presence of these compounds in fuels, the catalytic hydrodearomatization is one of the most important processes in refineries. In this context, the present work aims to study the hydrogenation of aromatic compounds in liquid phase employing catalysts based on base metals (Fe, Co, Ni) and noble metals (Ru, Pd, Pt) supported on Al2O3 by wet impregnation. Specifically, one has sought to evaluate the influence of the chemical composition, H2 reduction and reuse of the solids on its catalytic performances. Mono and bimetallic catalysts were prepared from chlorinated precursors by wet co-impregnation conducted at 353 K (80 °C) and pH of 10. During the wet impregnation, the solids were reduced with formaldehyde in liquid phase and subsequently reduced in situ or ex situ under H2. The prepared solids were characterized by potentiometric titration, N2 adsorption, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy and temperature programmed reduction. Catalysts performances were evaluated for toluene and aromatics mixture hydrogenations. The reactions were performed in a "slurry" Parr reactor under H2 pressure of 5 MPa (50 atm) and at a temperature of 373 K (100 °C) with the addition of water and solvents to the multiphase reaction medium. For toluene hydrogenation, Ru-based catalysts are much more active and selective to the product of the partial hydrogenation (methylcyclohexene). The effect of H2 reduction on the catalytic activity is shown dependent on the nature of the base metal, while the noble metal catalysts have decreases its activities. The addition of base metal to the Ru/Al2O3 catalysts also leads to a decrease in activity, but a synergetic effect is obtained with the Pt-Ru association. For the aromatics mixture hydrogenation, the reaction rate to Ru-Pt/Al2O3 catalyst follows the order: benzene > toluene > o-xylene > p-xylene. In this case, the addition of solvents to the reaction medium, as well as the reuse of the catalyst decreases the benzene and toluene hydrogenation rates, favoring the xylenes hydrogenation / Doutorado / Sistemas de Processos Quimicos e Informatica / Doutor em Engenharia Química

This work begins with an introduction to catalysis focusing on heterogeneous systems and surface science phenomena. A study on the partial oxidation reaction of n-butane to maleic anhydride (MA) is presented in the first part. MA supplies are barely adequate for market requirements due to continued strong demand. Only slight improvement in catalytic performance would be welcome in the industrial community. The vanadium phosphorus oxide (VPO) catalyst was used in this work. The reaction is highly exothermic and the need to properly support the catalyst, not only for good dispersion but adequate heat dissipation is of crucial importance. For this, alpha-SiC commercial powders were used in synthesizing the catalyst due to its high thermal conductivity. Up to 25% MA yields were obtained and the reaction temperature was lowered by up to 28% using SiC/VPO mixed catalysts. The second part of this work is focused on the Fischer-Tropsch synthesis (FTS) process using cobalt silica supported catalysts. The main objective is the production of synthetic ultra high purity jet fuel (JP5). This is a very timely topic given the energy issues our world is facing. Almost all aspects of the FTS process have been extensively studied, however the effects of calcination temperature and silica support structure on the catalyst performance are lacking in literature. The catalysts were prepared using various silica supports. The catalysts had different drying and calcination temperatures. It was found that lower support surface area and calcination temperature catalysts exhibited higher activity due to lower support cobalt phase interaction. Co/silica catalysts calcined at 573K showed the highest CO conversion and the lowest CH4 selectivity. Catalysts prepared with 300m²/g support surface area exhibited 79.5% C5+ selectivity due to higher reducibility and less metal support interaction. The properties and performance of various prepared catalysts in both VPO and Co/silica systems are characterized by FTIR, XRD, BET, GC and XPS techniques. Theoretical FTS deactivation by sintering calculations and SiC/VPO particle temperature gradient calculations are presented as well. Finally, conclusions and future work on improving the yield and selectivity and scaling up the bench top setups are also presented.

Abstract: Isobutylene is a high demand chemical that contributes to the production of fuel, plastic, and rubbers. It is produced industrially by different processes, as a byproduct of steam cracking of naphtha or a fluidized catalytic cracking or by isobutane dehydrogenation. Catalytic dehydrogenation of isobutane is in increasing importance because of the growing demand for isobutylene and the better economic advantage compared to other isobutylene production processes. Isobutane dehydrogenation is an endothermic reaction and to achieve good yields; it is preferred to work at higher temperatures. At these temperatures, carbon deposition leads to catalyst deactivation, which requires the catalyst to be regenerated on a frequent basis. Most of the current processes to produce isobutylene use either expensive platinum-based metal or toxic chromium-based catalysis. Hence, there is a demand to search for alternative catalysts that are a relatively cheap and non-toxic. To achieve this goal, Zirconia-supported Iron catalysts were prepared. To study the effect of active phase distribution, different iron loadings were tested for impregnation (3% to 10%) and co-precipitation (10%-20%). The catalysts show promising results that can achieve an isobutylene selectivity and yield of 91% and 31%, respectively, with isobutane conversion of 35%.