Polystyrene (PS) is one of the most important polymers in the plastic sector due to its inexpensive cost as well as many preferred properties. Its international market is expected to achieve $28.2 billion by 2019. Although PS has a high calorific value of 87 GJ tonne-1, there is no a practical method to manage its waste but landfill. As a result, the PS debris in the oceans has reached 70% of the total plastic debris. This issue is considered as the main economical and environmental drivers of converting polystyrene waste into renewable chemical feedstocks. The aim of this work is to develop a catalyst for converting PS into renewable chemicals under mild conditions. We introduce FeCu/Alumina with excellent catalytic activity to fully degrade polystyrene with 66% liquid yield at 250 °C. The GC/MS confirmed that the primary products are in the gasoline range. Next, we present the bimetallic FeCo/Alumina and successfully we have obtained 100% PS conversion and 90% liquid yield with maintaining the products selectivity. Later, the tri-metallic FeCuCo/Alumina was synthesized and showed 100% PS conversion and 91% liquid yield. Surprisingly, ethylbenzene was the major product in which 80 wt. % was achieved with excellent reproducibility. Furthermore, the real waste Styrofoam was thermally and catalytically degraded at 250 °C. Interestingly, a high styrene content of 78 wt. % was recovered after 30 minutes of the reaction under mild conditions. Keeping in mind that a good balance between acidity and basicity is required to convert PS into aromatic under mild reaction conditions catalytically. Finally, the performance of the catalysts was compared to literature reports and showed novel liquid yields. In conclusion, we have synthesized cheap, easy to scale up, and efficient catalysts to fully degrade PS into high liquid yields of aromatics with excellent selectivity.

Hidrocarbonetos aromáticos conhecidos como BTEX (benzeno, tolueno, etilbenzeno e xilenos) estão entre os maiores problemas de poluição ambiental. Estes compostos são reconhecidos por sua recalcitrância em ambientes anóxicos, e a remoção destes hidrocarbonetos, de sítios anaeróbios contaminados é dependente da atividade de uma população de microrganismos adaptados capazes de promover a biodegradação destes compostos, nestas condições. Neste sentido, o presente trabalho buscou purificar, caracterizar e utilizar cultura desnitrificante, como inóculo para desenvolvimento de biofilme, em reator anaeróbio de leito fixo preenchido com espumas de poliuretano, além de avaliar o potencial deste biofilme em promover a biodegradação dos compostos de BTEX. Células da cultura apresentaram coloração Gram negativa, com morfologia de cocos (diplococos e cocobacilos). A cultura foi capaz de crescer, sob condições desnitrificantes, utilizando diferentes substratos. A cultura não apresentou capacidade de crescer sob condições sulfetogênicas. Velocidades de crescimento ('mü') de 0,046/h e 0,050/h e tempos de geração (Tg) de 15,1 horas e 13,9 horas foram obtidos para as células crescidas em benzeno e etilbenzeno, respectivamente. A cultura purificada foi utilizada para formar biofilme em RAHLF. Em todas as condições de alimentação as quais os reatores foram submetidos houve remoção da matéria orgânica, nitrato e dos hidrocarbonetos. A menor eficiência de remoção de hidrocarbonetos foi de 89,4%, obtida durante a alimentação dos reatores com benzeno. A matéria orgânica (DQO) foi removida com eficiência média de 87,1%. A eficiência média de remoção de nitrato foi de 94%. O sequenciamento das amostras revelou que o biofilme do RAHLF1 foi formado, principalmente, por espécies de Paracoccus, Pseudomonas e Bacteroides, enquanto que no RAHLF2, alimentado com etilbenzeno, observou-se espécies dos gêneros: Paracoccus, Pseudomonas, Xanthomonas e Variovorax / The monoaromatic hydrocarbons known as BTEX (benzene, toluene, ethylbenzene, and xylene) are among the greatest environmental pollution problems. These compounds are known by their recalcitrance in anoxic environments, and the removal of these toxics from anaerobic contaminated sites depends on the presence of an adapted microbial population capable of to promote the biodegradation of these compounds under such condition. Thus, in the current study a denitrifying culture was purified, characterized and used as inoculum to form a biofilm in a horizontal-flow anaerobic immobilized biomass reactor filled with polyurethane foam, and to assess the potential of this biofilm to promote BTEX compounds biodegradation. Culture cells were Gram negative, with coccus (diplococcus and cocobacilli) morphology. The culture was able to grow, under denitrifying conditions, using different substrates. No growth was seen in sulfate-reducing conditions. Growth velocity('mü') of 0.046/h and 0.050/h, and generation time of 15.1 and 13.9 hours were obtained for cultures isolated in the presence of benzene and ethylbenzene, respectively. The purified culture was used to form a biofilm inside RAHLF. At all feeding conditions the reactors were submitted the organic matter, nitrate and hydrocarbons were removed. The smallest hydrocarbons removal efficiency was 89.4%, obtained during benzene feeding. The organic matter (COD) was removed with mean efficiency of 87.1%. The mean efficiency of nitrate removal was 94.0%. Sequencing of samples showed that the RAHLF1 biofilm was composed specially for Paracoccus, Pseudomonas and Bacteroides species. Biofilm of RAHLF2 reactor, obtained from ethylbenzene feeding, was composed by Paracoccus, Pseudomonas, Xanthomonas and Variovorax species

Submitted by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T18:32:41Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-09-15T18:36:32Z (GMT) No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) / Made available in DSpace on 2014-09-15T18:36:32Z (GMT). No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Carolina Freire Barbosa.pdf: 4193333 bytes, checksum: 9a2fe081d090bafb5a1537643a197424 (MD5) Previous issue date: 2014-03-11 / In this work, activated carbon beads were prepared through carbonization of styrene-divinylbenzene (Sty-DVB) copolymers synthesized in the presence of soybean oil as diluent and cobalt ferrite nanoparticles dispersed in the organic phase. Firstly, a cobalt ferrite gel was prepared through co-precipitation technique with posterior surfactant action by oleic acid. The copolymer and the composites containing cobalt ferrite were obtained through suspension polymerization. Four matrixes were obtained, which have the following differences: the cobalt ferrite content (2 or 5 %), the amount of hydroxyethylcellulose used in the synthesis and the realization or not of a purification step before thermal treatments. Soybean oil was chosen as diluents in order to evaluate its effects on the synthesized materials considering the polymerization possibility due fat acid unsaturations and its low volatility. All synthesized materials were characterized by the following analysis: DRX, FTIR, TGA, nitrogen adsorption measurements (specific surface area, pore volume and pore size distribution), MEV and catalytic activity in the ethyl-benzene dehydrogenation reaction. Further, the composites had metal content evaluate by AAS. The soybean oil and the ferrite gel had a strong influence on the textural properties of copolymers and their respective activated carbons. All obtained activated carbons were active in relation to ethylbenzene dehydrogenation reaction. However, the activated carbon obtained from pure copolymer, i.e., without cobalt ferrite, presented the highest specific surface area, catalytic activity and selectivity. This catalyst also had the best stabilization of catalytic properties during evaluated reaction time. / Neste trabalho, esferas de carvão ativado foram preparadas através da carbonização de copolímeros estireno-divinilbenzeno (Sty-DVB) sintetizados na presença de óleo de soja como diluente e de nanopartículas de ferrita de cobalto dispersas na fase orgânica. Inicialmente, preparou-se um gel de ferrita de cobalto através da co-precipitação da ferrita de cobalto e posterior surfactação da mesma por ácido oleico. O copolímero e os compósitos poliméricos contendo gel de ferrita de cobalto foram obtidos através da técnica de polimerização em suspensão. Quatro matrizes foram sintetizadas, diferenciando-se apenas quanto ao conteúdo de gel de ferrita de cobalto (2 ou 5%), quantidade de hidroxietilcelulose usada na síntese e realização ou não de uma etapa de purificação antes dos tratamentos térmicos. O óleo de soja foi escolhido como diluente, a fim de avaliar a interferência de suas propriedades nos materiais sintetizados considerando a possibilidade de polimerizar-se devido à insaturações dos ácidos graxos e a sua baixa volatilidade. Todos os materiais sintetizados foram submetidos à caracterização através de análises de DRX, FTIR, TGA, adsorção física de nitrogênio (medidas de área superficial específica, volume de poros e distribuição de tamanhos de poros), MEV e atividade catalítica na reação de desidrogenação do etilbenzeno. Além disso, os compósitos (copolímeros contendo gel de ferrita de cobalto) tiveram os teores de metais quantificados por AAS. Foi verificado que o óleo de soja e a presença do gel de ferrita durante a polimerização influenciam nas propriedades texturais dos copolímeros e dos carvões sintetizados. Todos os carvões ativados obtidos mostraram-se ativos na reação de desidrogenação do etilbenzeno. Entretanto, o carvão obtido do copolímero puro (sem ferrita de cobalto) foi o que apresentou maiores valores de área superficial específica, taxas de conversão e de seletividade, além de uma maior estabilização durante os testes catalíticos realizados.

Soil contamination with petroleum hydrocarbons is a common problem. Toxic compounds such as BTEXs are present in gasoline derivatives. They can move through the soil and contaminate the groundwater, especially if methanol is present. This problem is critical in permeable soil. Although leaching of BTEX compounds from soil to the water is almost temperature dependent, movement of methanol through the soil is not. Methanol can move through the porous soil and reach the groundwater in a short time. It can also dissolve and carry BTEX compounds through the porous soil. Therefore, fast cleanup of the permeable soil which is contaminated with BTEX and methanol is crucial. Chlorine dioxide is an oxidizer, which is easy to use and safe to transport; and may be considered as a treatment technique for soil cleanup. Keywords: Groundwater, soil contamination, BTEX compounds, methanol, chlorine dioxide, soil cleanup

Rapid development and growth of industrialization has brought immense enrichments in living standards of humans, however, improper planned development also brings along several environmental problems such as pollution of environment and excessive consumption of natural resources. Among all the others, uncontrolled utilization of water poses a severe threat to the coming generations. Past decades have witnessed water shortage in various countries of the world. Although about 80% of the earth’s surface is covered with water, around 97.2% of water is salty making it inappropriate for general usage. Among the rest of the 2.8%, which is present as fresh water on surface, a large proportion of it has been found to be severely polluted. The increasing demand of fresh water both for industrial and domestic usage adds great demand on the available groundwater. Moreover, the severe pollution of fresh water on the surface adds more stress on the available groundwater. In Australia, approximately 20% of water supply is from groundwater and in the case of Western Australia groundwater provides two thirds of its water supply needs. Thus, it is important to manage groundwater sources in Western Australia to achieve the optimum water utilization and maintain the water table and it is also essential to decide on an appropriate water budget. Groundwater flow modelling is an effective tool to get appropriate water distribution and, to examine effects from pumping on water levels and direction of groundwater flow paths, thereby helping in its proper management and utilization. Apart from monitoring the flow and utilization, groundwater flow modeling is also vital to keep the track of pollutant in the groundwater. Increasing surface pollution and landfill sites tend to pollute the groundwater due to leaching. / The above mentioned aspects formed the basis of the present research. A groundwater flow model was developed in Visual MODFLOW Premium to study the effect of three different types of soil in and around Perth region. This study also shows the hypothetical contaminated site model for benzene, toluene, ethylbenzene and xylene (BTEX) transport in Perth Superficial unconfined aquifer which includes three major aquifer sediments namely Bassendean Sand, Safety Bay Sand and Tamala Limestone. Among the four different contaminants it was observed that benzene is able to migrate quickly as compared to the other contaminants due to its smaller distribution coefficient. / This study also explored the major soil parameters such as effect of sorption, effective porosity and hydraulic conductivity on contaminant plume configuration and contaminants concentration for the three types of aquifer sediments. A critical comparison of the behaviour of the three different types of soils was also conducted. / Simulation results of sensitivity analysis have shown that sorption and hydraulic conductivity greatly affected the contaminant plume length and concentration of contaminants with much lesser effect shown by the effective porosity. The simulated results also showed that the movement of contaminant in Tamala Limestone is most rapid by comparing these three types of aquifer sediments together. Thus, it can be said that contaminated sites found in Tamala Limestone needs immediate remediation of contaminants to bring down the contaminants concentration in groundwater. / In brief, the thesis explores the current groundwater scenario in and around Perth region. Based on the information a hypothetical scenario simulation has critically analyzed the various parameters affecting the water and contaminant flow for the various soil parameters. The study is considered as a building block for further research on developing a remediation technique for groundwater contaminant treatment.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-08-30T16:14:19Z No. of bitstreams: 1 Tese de Doutorado - Sérgio Botelho de Oliveira.pdf: 18232715 bytes, checksum: b87397cefa6c939563af6c9f1aeaa634 (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-02T15:22:42Z (GMT) No. of bitstreams: 1 Tese de Doutorado - Sérgio Botelho de Oliveira.pdf: 18232715 bytes, checksum: b87397cefa6c939563af6c9f1aeaa634 (MD5) / Made available in DSpace on 2016-09-02T15:22:42Z (GMT). No. of bitstreams: 1 Tese de Doutorado - Sérgio Botelho de Oliveira.pdf: 18232715 bytes, checksum: b87397cefa6c939563af6c9f1aeaa634 (MD5) / Resinas de estireno e divinilbenzeno são materiais atrativos para muitos propósitos por causa das suas propriedades, variedade de grupos funcionais na superfície e porosidade, que podem ser controlados na síntese. Essas características também favorecem a produção de suportes e catalisadores baseados em carvão, com elevada áreas superficiais específicas e com grupos funcionais na superfície, que podem agir como sítios ativos. Eles podem ser usados em muitas reações, entre elas, a desidrogenação do etilbenzeno para produzir estireno. Esse monômero é comercialmente produzido pela desidrogenação do etilbenzeno em presença de vapor de água, mas este processo possui um custo elevado e, portanto, há a necessidade de novas alternativas de produção. A substituição do vapor pelo dióxido de carbono é uma das opções mais atrativas para diminuir o custo energético e, dessa forma, muitos estudos têm sido conduzidos para obter novos catalisadores para essa reação. Com este objetivo, neste trabalho foi descrita a preparação de catalisadores de cobre suportado em carvão ativado polimérico, assim como sua avaliação na desidrogenação do etilbenzeno em presença de dióxido de carbono. O carvão ativado polimérico foi preparado a partir do copolímero estireno e divinilbenzeno sulfonado, seguido da calcinação (250 oC), carbonização (900 oC) e ativação (800 oC). Os íons cobre foram adsorvidos nesse sólido por diversos métodos. O efeito dos metais alcalinos (magnésio e sódio) nas propriedades texturais e catalíticas dos sólidos foi também estudado. As amostras foram caracterizadas por espectrofotometria de absorção atômica, espectroscopia de infravermelho com transformada de Fourier, medidas de área superficial específica e de porosidade, difração de raios X, microscopia eletrônica de varredura e espectroscopia de energia dispersiva. Os catalisadores foram avaliados na desidrogenação do etilbenzeno em presença de dióxido de carbono, a 1 atm e em diversas temperaturas (400, 500 e 600oC). Foram obtidos sólidos com diferentes propriedades texturais e catalíticas, dependendo do método de preparação, assim como da presença de metais. O uso de uma razão de estireno/divinilbenzeno de 15/85 levou à produção de um carvão ativado com a elevada área superficial específica, capaz de adsorver grandes quantidades de cobre, devido aos grupos funcionais gerados na superfície. As propriedades texturais e catalíticas do carvão ativado com cobre foram fortemente dependentes do método de incorporação do cobre. O catalisador mais ativo foi produzido quando o cobre foi adsorvido no carvão ativado previamente oxidado por quatro vezes sucessivas, utilizando-se uma mistura de oxigênio em nitrogênio. Em ambos os sólidos CA e CON, o cobre e os grupos funcionais superficiais no carvão ativado foram ativos na reação. A adição do magnésio aumentou a seletividade a estireno, devido à neutralização de sítios ácidos residuais. O catalisador produzido foi mais ativo do que uma amostra de um catalisador comercial avaliado na presença de vapor, mostrando que o catalisador é promissor para fins industriais / Styrene and divinylbenzene resin is an attractive material for several purposes because of its properties, such as the variety of surface functional groups and porosity, which can be controlled during the synthesis. These characteristics also favor the production of carbon-based supports and catalysts with high specific surface areas and with functional groups on the surface, which can act as active sites. They can be used for several reactions, among them, the ethylbenzene dehydrogenation to produce styrene. This monomer is commercially produced by the ethylbenzene dehydrogenation in the presence of steam but it is a high cost process and thus new alternatives are much needed. The replacement of steam by carbon dioxide is one of the most attractive options to decrease the energy cost and thus several studies have been carried out to find new catalysts for this reaction. With this goal in mind, the preparation of catalysts based on polymeric activated carbon-supported copper, as well as their evaluation in ethylbenzene dehydrogenation in the presence of carbon dioxide, was described in this work. The polymeric activated carbon was prepared from sulfonated styrene- divinylbenzene copolymer, followed by calcination (250 oC), carbonization (900 oC) and activation (800 oC). Copper ions were adsorbed in these solids by several methods. The effect of alkaline metals (magnesium and sodium) on the textural and catalytic properties of the solids was also studied. Samples were characterized by atomic absorption spectrometry, Fourier transform infrared spectroscopy, specific surface area and porosity measurements, X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The catalysts were evaluated in ethylbenzene dehydrogenation in the presence of carbon dioxide at 1 atm and several temperatures (400, 500 and 600 oC). Solids with different textural and catalytic properties were obtained depending on the preparation method as well as on the presence of metals. The use of a styrene to divinylbenzene ratio of 15/85 leads to the production of an active carbon with the highest specific surface area, which is also able to adsorb a large amount of copper, due to the surface functional groups generated. The textural and catalytic properties of the activated carbon- supported copper largely depended on the method of the copper incorporation. The most active catalyst was produced when copper was adsorbed on activated carbon previously oxidized four times successive with a gas mixture of oxygen in nitrogen. In these solids CA and CON, both copper and the surface functional groups on the activated carbon were active for the reaction. The addition of magnesium increased the selective to styrene, due to the neutralization of the acidic sites on the surface, active for the production of toluene and benzene. The further rising of the catalyst with a sodium hydroxide solution increased the selectivity even more, due to the neutralization of the residual acidic sites. The catalyst produced was more active than a commercial sample evaluated in t

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-09-17T15:34:46Z No. of bitstreams: 1 _ TESE_ - Soraia Jesus de Oliveira - Versão Final com ficha catalográfica OK.pdf: 3092511 bytes, checksum: 4de5ad2f3ebfbeb60d029db00c51c206 (MD5) / Approved for entry into archive by Fatima Cleômenis Botelho Maria (botelho@ufba.br) on 2014-09-19T12:43:31Z (GMT) No. of bitstreams: 1 _ TESE_ - Soraia Jesus de Oliveira - Versão Final com ficha catalográfica OK.pdf: 3092511 bytes, checksum: 4de5ad2f3ebfbeb60d029db00c51c206 (MD5) / Made available in DSpace on 2014-09-19T12:43:31Z (GMT). No. of bitstreams: 1 _ TESE_ - Soraia Jesus de Oliveira - Versão Final com ficha catalográfica OK.pdf: 3092511 bytes, checksum: 4de5ad2f3ebfbeb60d029db00c51c206 (MD5) / FAPESB / A desidrogenação catalítica do etilbenzeno em presença de vapor d´água é, sem dúvida, a principal via de produção de estireno, um produto de alto valor comercial, amplamente utilizado na manufatura de borrachas e vários polímeros. Os catalisadores típicos comerciais são baseados em hematita (-Fe2O3) contendo óxido de cromo e óxido de potássio, que atuam como promotor textural e estrutural, respectivamente. Estes sistemas possuem diversas vantagens, tais como baixo custo e elevada resistência a venenos, mas apresentam algumas desvantagens, tais como a perda de potássio durante a reação, provocando a desativação do catalisador e a toxicidade do óxido de cromo. Visando a superar esses problemas, neste trabalho, foram preparados catalisadores de hematita dopada com magnésio, que foram avaliados na desidrogenação de etilbenzeno, a fim de obter sistemas isentos de cromo e de potássio para essa reação. Os catalisadores (Mg/Fe (molar)= 0; 0,01; 0,03; 0,06; 0,09 e 0,10) foram preparados por hidrólise simultânea de nitrato de ferro e de nitrato de magnésio, com hidróxido de amônio à temperatura ambiente, seguido de aquecimento a 600 °C. Os catalisadores foram caracterizados por análise química, espectroscopia no infravermelho com transformada de Fourier, difração de raios X, espectroscopia Mössbauer, medidas de área superficial específica, redução à temperatura programada e espectroscopia fotoeletrônica de raios X. Nas amostras com baixos teores de magnésio (Mg/Fe= 0,01 e 0,03) foram obtidos magnésia e cristais de hematita de 69 e 63 nm, respectivamente, enquanto na amostra com Mg/Fe= 0,06 foram produzidos cristais de hematita de 124 nm, co- existindo com ferrita de magnésio. Por outro lado, nas amostras mais ricas em magnésio (Mg/Fe= 0,09 e 0,1) foram obtidos cristais de hematita de 57 e 61 nm, respectivamente, co-existindo com magnésia e ferrita de magnésio. A adição de magnésio a catalisadores de hematita alterou a área superficial específica dos sólidos; a magnésia atua como um espaçador na produção de pequenos cristais de hematita. O magnésio também diminuiu a temperatura de redução da hematita mas não se observou uma tendência regular com o seu conteúdo. Em todos os catalisadores, o magnésio tende a depositar-se na superfície e este efeito aumenta com o seu teor, gerando superfícies sólidas parcialmente cobertas com magnésia e/ou ferrita de magnésio. Todos os catalisadores dopados com magnésio foram mais ativos que a hematita na desidrogenação de etilbenzeno, em presença de vapor d´água e seletiva ao estireno. A atividade e a seletividade da hematita variaram de forma irregular com o teor de magnésio, um fato que pode ser relacionado com as diferentes fases nos sólidos. Foi proposto que a magnésia atua como promotor textural, levando à produção de pequenos cristais de hematita, que são cataliticamente mais ativos, enquanto a ferrita de magnésio aumenta a atividade dos sítios de ferro devido às interações eletrônicas na estrutura do espinélio. A combinação destes efeitos conduz à formação do catalisador mais ativo (Mg/Fe= 0,9), consistindo de hematita parcialmente coberta por magnésia e ferrita de magnésio. Ele tem a vantagem de não ser tóxico, sendo promissor para aplicações comerciais. Além disso, o catalisador com o mais baixo teor de magnésio (Mg/Fe= 0,1), consistindo de hematita parcialmente coberta por magnésia, também é atrativo para aplicações comerciais, devido à sua elevada selectividade (quase 100%), o que pode evitar a reciclagem do etilbenzeno e as operações de separação, levando a uma redução nos custos operacionais / Catalytic ethylbenzene dehydrogenation in the presence of steam is by far the main route for the production of styrene, a high value chemical, widely used in the manufacture of several rubbers and polymers. The typical commercial catalysts are based on hematite (-Fe2O3) containing chromium oxide and potassium oxide which act as textural and structural promoter, respectively. These systems have several advantages such as low cost and high resistance to poisons but have some disadvantages such as potassium loss during reaction, leading to the catalyst deactivation and the toxicity of chromium oxide. In order to overcome these drawbacks, magnesium-doped hematite catalysts were prepared and evaluated in ethylbenzene dehydrogenation in this work, aiming to get chromium and potassium- free catalysts for the reaction. The catalysts (Mg/Fe (molar)= 0; 0.01, 0.03, 0.06, 0.09 and 0.10) were prepared by simultaneous hydrolysis of iron nitrate and magnesium nitrate with ammonium hydroxide at room temperature, followed by heating at 600 °C. The catalysts were characterized by chemical analysis, Fourier transform infrared spectroscopy, X-ray diffraction, Mössbauer spectroscopy, specific surface area measurements, temperature programmed reduction and X-ray photoelectronic spectroscopy. For the poorest-magnesium samples (Mg/Fe = 0.01 and 0.03) both magnesia and hematite crystals of 69 and 63 nm, respectively, were found while for the sample with Mg/Fe= 0.06 hematite crystals of around 124 nm were produced, coexisting with magnesium ferrite. Conversely, for the richest-magnesium samples (Mg/Fe = 0.09 and 0.1) hematite crystals of 57 and 61 nm, respectively, were found co-existing with magnesia and magnesium ferrite. The addition of magnesium to hematite-based catalysts changes the specific surface area of the solids, magnesia acts as a spacer to produce small crystals of hematite. Magnesium also decreases the reduction temperature of hematite but no regular tendency with its content was found. For all catalysts, magnesium tends to deposit on the surface, this effect increases with its amount, generating solid surfaces partially coated with magnesia and/or magnesium ferrite. All magnesium-doped catalysts were more active than pure hematite in ethylbenzene dehydrogenation in the presence of steam and selective to styrene. The activity and selectivity of hematite vary irregularly with magnesium content, a fact that can be related to the different phases in the solids. It was proposed that magnesia acts as textural promoter, leading to production of small crystals of hematite, which are catalytically more active while magnesium ferrite increases the activity of iron sites due to electronic interactions in the spinel structure. The combination of these effects leads to the most active catalyst (Mg/Fe = 0.9), consisting of hematite partially covered by magnesia and magnesium ferrite. It has the advantage of not being toxic and then is promising for commercial applications. In addition, the magnesium-poorest catalyst (Mg/Fe = 0.1), consisting of hematite partially covered by magnesia, is also attractive for commercial application due to its high selectivity (almost 100%), which could prevent ethylbenzene recycle and separation operations, leading to a reduction in operating costs.

Orientador: Teresa Massako Kakuta Ravagnani / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-08T19:44:43Z (GMT). No. of bitstreams: 1 Araujo_PauloJardelPereira_M.pdf: 1672087 bytes, checksum: 39df6a7017efe009f53dbd9aecb301b1 (MD5) Previous issue date: 2007 / Resumo: Estireno é um importante monômero na fabricação de termoplásticos e borrachas sintéticas. Grande parte de sua produção é baseada na desidrogenação catalítica do etilbenzeno. O aumento da produtividade do estireno pode ser alcançado utilizando-se membranas permseletivas para remoção do hidrogênio, suprimindo as reações reversíveis e secundárias. Este trabalho apresenta a simulação do processo de desidrogenação em um reator tubular de leito fixo catalítico envolto em membrana composta permseletiva. A modelagem matemática desenvolvida considera os diferentes mecanismos de transporte de massa que prevalecem nas várias camadas da membrana e no leito fixo catalítico. A remoção do Hidrogênio do leito catalítico foi realizada estabelecendo-se um gradiente de potencial químico de hidrogênio através da membrana. Duas formas de remoção de hidrogênio foram estudadas: pela aplicação de uma diferença de pressão através da membrana e pelo arraste com gás inerte. Um programa computacional foi implementado para descrever os perfis de temperatura, pressão e concentração ao longo de todo o reator, bem como a conversão do etilbenzeno, seletividade e produtividade de estireno. Comparando os resultados obtidos no leito fixo convencional operando na condição industrial padrão com os obtidos na aplicação de diferença de pressão através da membrana, observou-se um acréscimo na conversão de etilbenzeno de 19,89 % na mesma seletividade do estireno, representando um aumento de 19,12 % na produtividade de estireno. Este mesmo aumento foi também alcançado com o uso de gás de arraste inerte. Por este motivo, este procedimento é a opção mais recomendada, por agregar custo menor ao processo. Através da simulação do sistema em diferentes condições do processo e configurações do reator e da membrana, obteve-se um acréscimo de 40,98 % na produtividade de estireno comparada a do processo com leito fixo convencional / Abstract: Styrene is an important monomer in the manufacture of thermoplastic and synthetic rubbers. Most of the production is based on the catalytic dehydrogenation of ethylbenzene. The increase of the styrene productivity can be reached using permselectives membranes for hydrogen removal, suppressing the reversible and secondary reactions. This work presents the simulation of dehydrogenation process in tubular fixed bed reactor wrapped with permselective composite membrane. The mathematical modeling was developed considering the different mechanisms of mass transport that prevail in several membrane layers and in catalytic fixed bed. The removal of the permeated hydrogen was carried out establishing a gradient of chemical hydrogen potential through the membrane. Two forms of hydrogen removal were studied: the application of transmembrane pressure drop and the employment of inert sweep gas. A computational program was implemented to describe the profiles of temperature, pressure and concentration throughout all reactor, as . well as the ethylbenzene conversion, styrene selectivity and productivity. Comparing the simulation results obtained for conventional fixed bed reactor carried on standard industrial operation condition with application transmembrane pressure drop form, it shows an increase of 19.89 % in ethylbenzene conversion in the same styrene selectivity for, meaning an increase of 19.12% in styrene productivity. The same addition was obtained when the inert sweep gas was employed. Therefore, this last proceeding has been recommended as the better option, due to its lower operation cost. Through the system simulation at various operation conditions, using different reactor and membrane configurations, an increase of 40.98 % in the styrene productivity was reached comparing to conventional fixed bed process / Mestrado / Sistemas de Processos Quimicos e Informatica / Mestre em Engenharia Química

Hidrocarbonetos aromáticos conhecidos como BTEX (benzeno, tolueno, etilbenzeno e xilenos) estão entre os maiores problemas de poluição ambiental. Estes compostos são reconhecidos por sua recalcitrância em ambientes anóxicos, e a remoção destes hidrocarbonetos, de sítios anaeróbios contaminados é dependente da atividade de uma população de microrganismos adaptados capazes de promover a biodegradação destes compostos, nestas condições. Neste sentido, o presente trabalho buscou purificar, caracterizar e utilizar cultura desnitrificante, como inóculo para desenvolvimento de biofilme, em reator anaeróbio de leito fixo preenchido com espumas de poliuretano, além de avaliar o potencial deste biofilme em promover a biodegradação dos compostos de BTEX. Células da cultura apresentaram coloração Gram negativa, com morfologia de cocos (diplococos e cocobacilos). A cultura foi capaz de crescer, sob condições desnitrificantes, utilizando diferentes substratos. A cultura não apresentou capacidade de crescer sob condições sulfetogênicas. Velocidades de crescimento ('mü') de 0,046/h e 0,050/h e tempos de geração (Tg) de 15,1 horas e 13,9 horas foram obtidos para as células crescidas em benzeno e etilbenzeno, respectivamente. A cultura purificada foi utilizada para formar biofilme em RAHLF. Em todas as condições de alimentação as quais os reatores foram submetidos houve remoção da matéria orgânica, nitrato e dos hidrocarbonetos. A menor eficiência de remoção de hidrocarbonetos foi de 89,4%, obtida durante a alimentação dos reatores com benzeno. A matéria orgânica (DQO) foi removida com eficiência média de 87,1%. A eficiência média de remoção de nitrato foi de 94%. O sequenciamento das amostras revelou que o biofilme do RAHLF1 foi formado, principalmente, por espécies de Paracoccus, Pseudomonas e Bacteroides, enquanto que no RAHLF2, alimentado com etilbenzeno, observou-se espécies dos gêneros: Paracoccus, Pseudomonas, Xanthomonas e Variovorax / The monoaromatic hydrocarbons known as BTEX (benzene, toluene, ethylbenzene, and xylene) are among the greatest environmental pollution problems. These compounds are known by their recalcitrance in anoxic environments, and the removal of these toxics from anaerobic contaminated sites depends on the presence of an adapted microbial population capable of to promote the biodegradation of these compounds under such condition. Thus, in the current study a denitrifying culture was purified, characterized and used as inoculum to form a biofilm in a horizontal-flow anaerobic immobilized biomass reactor filled with polyurethane foam, and to assess the potential of this biofilm to promote BTEX compounds biodegradation. Culture cells were Gram negative, with coccus (diplococcus and cocobacilli) morphology. The culture was able to grow, under denitrifying conditions, using different substrates. No growth was seen in sulfate-reducing conditions. Growth velocity('mü') of 0.046/h and 0.050/h, and generation time of 15.1 and 13.9 hours were obtained for cultures isolated in the presence of benzene and ethylbenzene, respectively. The purified culture was used to form a biofilm inside RAHLF. At all feeding conditions the reactors were submitted the organic matter, nitrate and hydrocarbons were removed. The smallest hydrocarbons removal efficiency was 89.4%, obtained during benzene feeding. The organic matter (COD) was removed with mean efficiency of 87.1%. The mean efficiency of nitrate removal was 94.0%. Sequencing of samples showed that the RAHLF1 biofilm was composed specially for Paracoccus, Pseudomonas and Bacteroides species. Biofilm of RAHLF2 reactor, obtained from ethylbenzene feeding, was composed by Paracoccus, Pseudomonas, Xanthomonas and Variovorax species

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