Orientador: Melissa Gurgel Adeodato Vieira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química / Made available in DSpace on 2018-08-24T22:58:23Z (GMT). No. of bitstreams: 1 Stofela_SaraKarolineFigueiredo_M.pdf: 3437110 bytes, checksum: 75c3b9d81bd674bc6b2d46a4347ba152 (MD5) Previous issue date: 2014 / Resumo: Resíduos contaminados com compostos orgânicos, sendo grande parte formados por hidrocarbonetos aromáticos, como o benzeno, tolueno e xileno, vem sendo gerados em grandes quantidades nas indústrias e em derramamentos de postos de estocagem de combustíveis. Sendo assim, surge espaço para novas pesquisas de tratamento desses efluentes, como a adsorção em argilas organofílicas. Portanto, o objetivo deste trabalho é avaliar o potencial da argila organofílica Spectrogel na adsorção dos compostos BTX. Para este estudo foram realizados teste de hidratação e expansão em meio orgânico, estudo do efeito do pH, avaliação do potencial de remoção e estudo cinético, por meio de ensaios cinéticos de adsorção monocomposto, bicompostos e tricompostos, estudo de equilíbrio, atráves de ensaios de equilíbrio monocomposto, bicompostos e tricompostos, nas temperaturas de 15, 25 e 35 oC, estudo termodinâmico, caracterização do material adsorvente antes e após os ensaios de adsorção, estudo de regeneração do adsorvente, e análise estatística do processo de adsorção. A argila apresentou uma eficiência de remoção de 95%, 89% e 96% para o benzeno, tolueno e xileno, respectivamente e mostrou que o processo é rápido com no máximo 120 min para atingir o equilíbrio. No estudo cinético, tanto o modelo pseudoprimeira-ordem, quanto o pseudossegunda ordem apresentaram boas correlações. O modelo de difusão intrapartícula e modelo de Boyd indicaram que a adsorção é controlada tanto pela difusão intrapartícula, como pela difusão externa. O estudo de equilíbrio indicou que o xileno é o contaminante com maior afinidade pelo meios adsorvente. Entre os modelos de isotermas utilizados nos ajustes dos dados experimentais, o modelo de Dubinin-Radushkevitch foi o que apresentou melhor correlação para todas as isotermas monocomposto. Para as isotermas bicompostos, o modelo de Freundlich foi o que melhor se ajustou. Os parâmetros termodinâmicos mostraram que o processo de adsorção de BTX em argila Spectrogel é espontâneo e endotérmico. A caracterização do adsorvente após a adsorção dos BTX mostrou que o mesmo é pouco poroso e possui a superfície heterogênea, evidenciando a presença dos compostos BTX e algumas mudanças estruturais no material adsorvente. Por fim, os ensaios de regeneração indicaram a regeneração do adsorvente por meio do eluente etanol / Abstract: Contaminated waste with organic compounds, being largely composed of aromatic hydrocarbons such as benzene, toluene and xylene, has being generated in large quantities in industries and spills fuel storage stations. Thus, it arises space for further research about treatment of these effluents, such as adsorption on organoclay. Therefore, the aim of this study is to evaluate the adsorption of BTX compounds into organoclay Spectrogel. For this study tests of hydration and expansion in organic media and tests of the effect of pH were conducted. Equilibrium study was also performed by tests of mono-component, bi-component and multicomponent solutions at temperatures of 15, 25 and 35 oC. The adsorbent was characterized before and after the adsorption experiments. Finally, the regeneration of the adsorbent through eluents and a statistical study of the adsorption process were also performed. The evaluation of the potential removal provided a removal efficiency of 95%, 89% and 96% for benzene, toluene and xylene, respectively and showed that the process is fast taking a maximum of 120 min to reach equilibrium. In the kinetic study, both the pseudo first order model, as well as pseudo second order model showed a good correlation. The intraparticle diffusion model and Boyd model indicated that adsorption is controlled by both intraparticle diffusion and external diffusion. The equilibrium study indicated that xylene is the most competitive contaminant by active adsorption site. Among the isotherm models used, only the Dubinin-Radushkevitch showed a good correlation for all mono-component isotherms. For bi-component isotherms, the Freundlich model showed the best fit. The thermodynamic parameters indicated that the adsorption process of BTX into clay is spontaneous and endothermic. The characterization of the study showed that the this adsorbent is porous and presents a heterogeneous surface after adsorption and the presence of BTX compounds and structural changes were observed in the adsorbent material after process. The dessorption tests indicated a possible regeneration of the adsorbent using ethanol as eluent.z / Mestrado / Desenvolvimento de Processos Químicos / Mestra em Engenharia Química

[EN] This thesis focusses on reactive processes catalysed by zeolites to obtain and convert BTX aromatics. These compounds, together with light olefins, are the pillars of the petrochemical and organic chemical industry, as they are the raw materials to produce basic intermediates, such as polyester monomers, polyamides, engineering plastics and intermediate products for the manufacture of detergents, pharmaceuticals, fertilizers, and explosives. Currently, the aromatics and light olefins are obtained mainly from petroleum refining, natural gas or coal. Along the last decades, natural gas conversion into higher value chemicals has gained importance, such as olefins and aromatics. The main reasons are its high hydrogen to carbon (H/C), its composition, which is independent of the source, and its availability, as world reserves are larger than those of oil, especially if shale gas is considered. Therefore, the methane aromatization reaction (MDA) is studied as a route for obtaining aromatics. The most widely used catalyst for this reaction is Mo/H-ZSM-5. Thus, the effect of various parameters on the catalyst activity has been studied, such as the physico-chemical properties of the parent sample and the metal component incorporation procedure, in order to find the optimum catalyst Mo/ZSM-5. Moreover, this study has allowed correlating successfully amount and nature of the two active centers involved in this reaction with methane conversion and product distribution. On the other hand, one of the mayor drawbacks of this reaction is the strong deactivation of the catalyst; therefore, a study of the regeneration possibilities has been carried out and has allowed the design of an effective protocol to prolong the catalyst life and with the aim of expanding its industrial applications. Furthermore, other medium pore and multipore zeolitic structures have been studied as alternative to ZSM-5 zeolite, and their catalytic behavior has been successfully correlated with their topologies. Regarding the transformation and redistribution of the BTX aromatics, alkylation, disproportionation and isomerization reactions have been studied, which employ acid zeolites as catalyst to obtain alkylaromatics with high interest for the petrochemical industry, such as xylenes, ethylbenzene, cumene, ethyltoluene and cymene. The main zeolites used in these processes at commercial scale are ZSM-5, MCM-22, Beta and MOR. Therefore, new zeolitic materials have been studied considering the molecular dimension of reactants, products and reaction intermediates, as well as the dimensions of the zeolite's pore topologies. Multipore zeolites have also been included in this study, due to the potential "molecular traffic control" type of selectivity that can be improved by these structures presenting interconnected channel apertures of different size. The best performing zeolitic structures for these processes are ITQ-13, ITQ-22, ITQ-39 and ITQ-47, which due to their good catalytic behavior, could be considered as an attractive alternative to be used as catalysts on commercial scale. / [ES] La presente tesis doctoral se centra en procesos reactivos catalizados mediante zeolitas para la obtención y transformación de aromáticos (fracción BTX). Estos compuestos son, junto con las olefinas ligeras, los pilares sobre los que se basa la industria petroquímica y de química orgánica en general, pues son la materia prima para muchos productos, tales como monómeros de poliésteres, poliamidas, plásticos de ingeniería, y productos intermedios para la fabricación de detergentes, fármacos, fertilizantes, y explosivos. Actualmente los aromáticos y las olefinas se obtienen principalmente del refino del petróleo, del gas natural o del carbón. En las últimas décadas ha ganado importancia la transformación del gas natural a productos químicos de mayor valor añadido, tales como olefinas y aromáticos, en parte debido a su elevada relación hidrógeno-carbono (H/C), a que su composición es independiente de la fuente de donde provenga, y a que las reservas mundiales de gas natural son superiores a las de petróleo, especialmente si se tiene en cuenta el gas pizarra. En la presente tesis, se ha estudiado la reacción de aromatización de metano (MDA) como una alternativa para la obtención de aromáticos. El catalizador más empleado para esta reacción es Mo/H-ZSM-5. Así, se ha estudiado la influencia de diversos parámetros en la actividad catalítica del mismo (propiedades físico-químicas de la zeolita de partida y método de incorporación del componente metálico) con el objetivo de buscar el catalizador Mo/ZSM-5 óptimo. Este estudio ha permitido correlacionar los dos tipos de centros activos involucrados en esta reacción con la conversión de metano y la formación de productos. Uno de los grandes inconvenientes que presenta esta reacción es la fuerte desactivación que sufre el catalizador, por lo que se ha realizado un estudio de las posibilidades de regeneración del mismo, lo que ha permitido diseñar un protocolo de trabajo útil para alargar la vida del catalizador y ampliar sus posibilidades de aplicación a nivel industrial. Además, se ha estudiado el empleo de otros materiales zeolíticos con estructuras de poro medio y multiporo como posibles alternativas a la ZSM-5, y se ha correlacionado su comportamiento catalítico con las distintas topologías. Dentro del marco de las reacciones de transformación y redistribución de aromáticos (BTX), se han estudiado reacciones para la obtención de alquilaromáticos de gran interés para la industria petroquímica, tales como xilenos, etilbenceno, cumeno, etiltolueno y cimeno, mediante reacciones de alquilación, desproporcionación e isomerización, donde se implican zeolitas como catalizadores ácidos. Las zeolitas principalmente empleadas en estos procesos a escala industrial son ZSM-5, MCM-22, Beta y MOR. Por lo tanto, se han estudiados nuevos materiales zeolíticos como catalizadores alternativos en estos procesos, teniendo en cuenta las dimensiones moleculares de los reactantes, productos e intermedios de reacción requeridos, conjuntamente con las dimensiones topológicas de las estructuras zeolíticas. También se han incluido en este estudio zeolitas multiporo, muy interesantes por permitir controlar el tráfico molecular a través de las diferentes aperturas de sus canales. En estos procesos reactivos, han destacado las zeolitas ITQ-13, ITQ-22, ITQ-39 e ITQ-47 por presentar un buen comportamiento catalítico, planteándose como posibles alternativas a los catalizadores empleados a escala industrial. / [CAT] La present tesi doctoral es centra en processos reactius catalitzats mitjançant zeolites per a l'obtenció i transformació d'aromàtics (fracció BTX). Estos compostos són, juntament amb les olefines lleugeres, els pilars sobre els que es basa la indústria petroquímica i de química orgànica en general, doncs són la matèria prima per a molts productes, com són monòmers de polièsters, poliamides, plàstics d'enginyeria, i productes intermedis per a la fabricació de detergents, fàrmacs, fertilitzants, i explosius. Actualment els aromàtics i les olefines s'obtenen principalment del refinatge del petroli, del gas natural o del carbó. En les últimes dècades ha guanyat importància la transformació del gas natural a productes químics de major valor afegit, com són les olefines i els aromàtics. Açò es degut a la seua elevada relació hidrogen-carbó (H/C), a que la seua composició és independent de la font d'on provinga, i a que les reserves mundials de gas natural són superiors a les del petroli, especialment si es té en compte el gas pissarra. En la present tesi, se ha estudiat la reacció de aromatització de metà (MDA) com alternativa per a l'obtenció d'aromàtics. El catalitzador més emprat per a esta reacció és el Mo/H-ZSM-5. Per la qual cosa s'ha estudiat la influència de diversos paràmetres en l'activitat catalítica (propietats fisicoquímiques de la zeolita de partida i mètode de incorporació del component metàl·lic) amb l'objectiu de buscar el catalitzador òptim de Mo/ZSM-5. Este estudi ha permès correlacionar els dos tipus de centres actius involucrats en esta reacció amb la conversió de metà y la formació de productes. Un del grans inconvenients que presenta esta reacció és la forta desactivació que sofreix el catalitzador, per la qual cosa s'ha realitzat un estudi de les possibilitats de regeneració d'aquest, el que ha permès dissenyar un protocol de treball útil per allargar la vida del catalitzador i ampliar les seves possibilitats d'aplicació a nivell industrial. A més a més, s'ha estudiat l'ús d'altres materials zeolítics amb estructura de porus mitjà i multiporo com possibles alternatives a la ZSM-5, i s'ha correlacionat el seu comportament catalític amb les diferents topologies. Dins del marc de les reaccions de transformació i redistribució d'aromàtics (BTX), s'han estudiat reaccions per l'obtenció d'alquilaromàtics de gran interès per a la indústria petroquímica, com són xilè, etilbenzè, cumè, etiltoluè i cimè, mitjançant reaccions d'alquilació, desproporcionació o isomerització, on s'impliquen zeolites com catalitzadors àcids. Les zeolites principalment utilitzades en aquests processos a escala industrial són ZSM-5, MCM-22, Beta i MOR. Per tant, s'han estudiat nous materials zeolítics com a catalitzadors alternatius en estos processos, tenint en compte les dimensions moleculars dels reactants, productes i intermedis de reacció requerits, conjuntament amb les dimensions topològiques de les estructures zeolítiques. També s'han inclòs en este estudi zeolites multiporo, molt interessants per permetre controlar el tràfic molecular a través de les diferents obertures dels seus canals. En estos processos reactius, han destacat les zeolites ITQ-13, ITQ-22, ITQ-39 i ITQ-47 per presentar un bon comportament catalític, plantejant-se com a possibles alternatives als catalitzadors emprats a escala industrial. / Portilla Ovejero, MT. (2015). Zeolitas para la obtención y redistribución de aromáticos en la fracción BTX [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/59471 / TESIS

<p>This work studies propene aromatization reaction on H-MFI (Si/Al = 40) and physical mixtures of H-MFI (Si/Al = 40) and PtZn/SiO2 (2 wt% Pt, 3 wt% Zn) at 723 K - 823 K and 3 kPa C3H6. The influence of PtZn alloy (dehydrogenation function) is investigated on the product distribution and selectivity of metal-acid catalyzed propene aromatization. Typical product distribution consists of methane, ethane, ethene, propane, C4-C6 alkanes and alkenes, and benzene, toluene, xylene (BTX). On comparing the BTX carbon selectivity over the two catalysts at first equivalent space velocity and then equivalent propene conversion, higher BTX selectivities are observed on PtZn+H-MFI than H-MFI in both the cases. The higher BTX selectivities were previously attributed in the literature to the dehydrogenation pathway on the metal function. However, space velocity is an inadequate descriptor of reaction progress because the conversion of reactants can be different at same space velocity. Similarly, propene conversion is an incomplete descriptor for reaction progress because intermediates such as ethene and C4-C6 hydrocarbons react to form higher molecular weight hydrocarbons and subsequent aromatics as the reaction progresses. Such reactive hydrocarbons were lumped together as reactive intermediates and the remaining hydrocarbons were classified as non-reactive species or products. When BTX selectivities over PtZn-H-MFI and H-MFI are compared at equivalent temperature and equivalent conversion of all the reactive intermediates, both the catalysts exhibit similar BTX selectivities, suggesting that the presence of the dehydrogenation metal function doesn’t influence the selectivity towards BTX products. Further, we hypothesize cyclohexene as an intermediate in aromatic formation and use cyclohexene conversion as a probe reaction to understand how aromatics are formed over Brønsted acid sites and PtZn alloy. Cyclohexene conversion results at 723 K and 823 K shows the presence of an alternate route of aromatic formation via dehydrogenation of cycloalkenes, and this dehydrogenation pathway has an order of magnitude higher rates than the hydride transfer route on Brønsted acid sites. Further, we propose dominant reaction pathways of C1 – BTX hydrocarbon formation on H-MFI and bifunctional PtZn+H-MFI. Finally, we discuss the implications of using PtZn+H-MFI on developing a commercial propylene aromatization process and provide our recommendations for chemical and fuel production. In summary, these findings reveal previously unknown mechanistic details of metal bifunctionality for propene aromatization catalysis.  </p>

The increasing production of natural gas liquids attracts both academia and industry to develop on-purpose techniques converting those light alkanes to value-added chemicals. Dehydroaromatization is an alternative path for light alkane conversion to produce aromatics but still lacks active and stable catalysts. This work aims at the development of efficient dehydroaromatization catalysts by tuning the metal/acid bifunctionality of the Pt/HZSM-5 catalyst. Additionally, through co-processing light alkane with ammonia during the dehydroaromatization process, this study also proposes a new reaction system that could directly link the C-N bond for nitrile synthesis. The results suggested that the activity, selectivity, and stability of the monometallic Pt/HZSM-5 catalyst are highly dependent upon the Pt loading, the limit loading of 100 ppm is required to maintain sufficient metal functionality. To further minimize the Pt loading, the chemical properties of the Pt species were tuned by a second metal such as Zn or Cu. Consequently, the activity and stability of the catalyst are enhanced by orders of magnitude and the maximized metal functionality was achieved at Pt loading of 10 ppm. Characterizations show that Pt can be atomically dispersed as a hybrid [Pt1-Zn6] cluster in the Pt-Zn@HZSM-5 or forming single atom alloy type [Pt1-Cu4] ensembles in the Pt-Cu@HZSM-5. Specifically, the initial turnover frequencies of propane and ethane to BTX are up to 178.8 and 128.7 s-1 over the Pt-Cu@HZSM-5, up to 3-4 orders of magnitude higher than the state-of-the-art Pt-based catalyst. Furthermore, the deactivated catalyst can be continuously regenerated, demonstrating excellent stability of such a catalyst under hash oxidation conditions for coke burn-off. A new catalytic system named ammodehydrogenation (ADeH) for ethane selective conversion to acetonitrile, ethylene, and hydrogen over a bifunctional catalyst is proposed. Ethane ADeH over the Pt/HZSM-5 catalyst is active at low temperatures and atmospheric pressure for CH3CN production. The Pt/HZSM-5 shows high coke-resistibility during the ethane ADeH due to the strong interaction of NH3 with the acid sites of the catalyst. The catalyst can be further optimized by adding Co, the Pt-Co/HZSM-5 catalyst on ethane ADeH indicating that an appropriate balance between the metal and acid functionalities is critical for ethane ADeH.

The advancements of chemists, engineers, and material scientists has yielded an enormous and diverse library of high-performance materials with varying chemical and physical properties that can be used in a wide array of applications. A molecular-level understanding of the nature of gas–surface interactions is critical to the development of next generation materials for applications such as gas storage and separation, chemical sensing, catalysis, energy conversion, and protective coatings. Quartz crystal microbalance (QCM) and in situ infrared (IR) spectroscopic techniques were employed to probe how topological features of a material as well as structural differences of the analytes affect gas sorption. Detailed studies of the interactions of three categories of molecules: aromatic hydrocarbons, triatomic ambient gases, and chemical warfare agents, with metal-organic frameworks (MOFs) and polyurethane coatings were conducted to build structure–property relationships for the nature and energetics of gas sorption within each material. Differences in the molecular structure of the guest compounds were found to greatly influence how, and to what extent each molecule interacts with the MOF or polyurethane film. Specifically, IR studies revealed that transport of aromatic compounds within the zirconium-based MOF, UiO-66 was limited by steric restrictions as molecules passed through small triangular apertures within the pore environment of the MOF. In contrast, the smaller triatomic molecules, CO2, SO2, and NO2, were able to pass freely through the MOF apertures and instead reversibly adsorbed inside the MOF cavities. Specifically, SO2 and NO2 were observed to preferentially bind to undercoordinated zirconium sites located on the MOF nodes. In addition, uptake of CO2, SO2, and NO2 was also aided by dispersion forces within the confined pore environments and by hydrogen bond formation with μ3 OH groups of the MOFs. Dimethyl chlorophosphate (DMCP), a nerve agent simulant that contains several electronegative moieties, was also found to strongly adsorb to undercoordinated zirconium; however, unlike in the aromatic and triatomic molecule systems, DMCP remained permanently bound to the MOFs, even at high temperatures. Finally, QCM studies of mustard gas simulant uptake into polyurethane films of varying hard:soft segment compositions revealed that dipole-dipole and dipole-induced dipole interactions were responsible for favorable absorption conditions. Furthermore, the ratio of hard and soft segment components of the polyurethane had a minor impact on simulant adsorption. Higher hard-segment content resulted in a more crystalline film that reduced simulant uptake, whereas the rubbery, high soft segment polyurethane allowed for greater vapor absorption. Ultimately, molecular-level insight into how the chemical identity of a guest molecule impacts the mechanism and energetics of vapor sorption into both MOFs and polymeric films can be extended to other relevant systems and may help identify how specific characteristics of each material, such as size, shape, and chemical functionality impact their potential use in targeted applications. / Doctor of Philosophy / The nature in which specific gases interact with materials will largely dictate how the material can be utilized. By understanding where and how strongly gas molecules interact with a material, scientists and engineers can rationally design new and improved systems for targeted applications. In the research described in this thesis, we examined how the chemical structure of three different groups of compounds, which have relevance in many industrial, environmental, and defense-related applications, affected the type and strength of interaction between the gas and material of interest. From these studies, we have identified how key properties and features within the examined materials such as size, shape, and chemical composition, lead to significant differences in how vapor molecules interacted with the materials. For example, benzene, toluene, and xylene, which are incredibly important chemicals in industry, were found to be restricted by narrow passageways as they moved through materials with small pores. In contrast, small gases present in the environment from combustion exhaust such as CO₂, SO₂, and NO₂ were able to freely traverse through the passageways, and instead weakly interacted with specific chemical groups inside the cavities of the material. On the same material however, a third class of compounds, organophosphorus-containing chemical warfare agent mimics, irreversibly reacted with chemical groups of the surface, and remained bound even after exposure to high temperatures. Ultimately, the work presented in this thesis is aimed at providing key fundamental insights about specific classes of materials on how, and how strongly they interact with targeted hazardous vapors, which can be utilized by synthetic chemists to design next generation materials.

Dans une bioraffinerie, la biomasse peut être transformée par différents procédés (thermiques, chimiques et biochimiques) en carburants et en produits chimiques à haute valeur ajoutée. Plus spécifiquement, le procédé catalytique d'hydrodésoxygénation (HDO) devrait permettre de valoriser à la fois les bio-huiles obtenues par pyrolyse en biocarburants, ainsi que les composés aromatiques oxygénés issus de la dépolymérisation de la lignine en aromatiques simples.Afin de modéliser la désoxygénation de ces fractions, les isomères du crésol (ortho-, méta- et para-crésol) ont été choisis comme molécules oxygénés modèles. Les réactions ont été effectuées sous haute pression (2-4 MPa) et à des températures comprises entre 250 et 340° C. Plusieurs phases actives à base de molybdène (sulfures et oxyde) et de nickel (métallique et phosphure) ont été étudiées. L'influence du support des phases oxydes de molybdène (SiO2, SBA-15, Al2O3) et des phases à base de nickel (SiO2 et ZrO2) a également été examinée.Dans ces conditions expérimentales, les composés phénoliques sont désoxygénés selon deux voies de transformations parallèles. La voie de désoxygénation directe (DDO) conduit uniquement au toluène par hydrogénolyse de la liaison C-O. La voie hydrogénante (HYD), quant à elle, conduit à un mélange de produits obtenus après hydrogénation du cycle aromatique, impliquant des réactions d'hydrogénolyse, d'hydrogénation, de déshydratation et d'isomérisation. L'activité des catalyseurs ainsi que la contribution de chaque voie de désoxygénation sont dépendantes de la phase active étudiée, du support choisi ainsi que des conditions opératoires utilisées. / In a biorefinery, biomass can be converted by different process (thermal, chemical and biochemical) into fuels and valued-added chemicals. More specifically, the catalytic hydrodeoxygenation (HDO) process could upgrade both bio-oils obtained from pyrolysis into biofuels and oxygenated aromatic compounds from the depolymerization of lignin into aromatics.In order to model the deoxygenation of these fractions, the cresol isomers (ortho, meta and para-cresol) were chosen as model oxygenated molecules. The reactions were carried out under high pressure (2-4 MPa) and temperatures between 250 and 340° C. Several active phases based on molybdenum (sulphides and oxide) and nickel (metal and phosphide) have been studied. The influence of the support of the molybdenum oxide phases (SiO2, SBA-15, Al2O3) and of the nickel-based phases (SiO2 and ZrO2) was also examined.Under these experimental conditions, phenolic compounds are deoxygenated by two parallel pathways. The direct deoxygenation (DDO) route only leads to toluene by hydrogenolysis of the C-O bond. The hydrogenating route (HYD), on the other hand, leads to a mixture of products obtained through the hydrogenation of cresol aromatic ring, involving hydrogenolysis, hydrogenation, dehydration and isomerization reactions. The activity of the catalysts as well as the contribution of each deoxygenation pathway are dependent on the active phase studied, on the support chosen as well as on the operating conditions used.

Made available in DSpace on 2014-12-17T15:01:26Z (GMT). No. of bitstreams: 1 Bruna_CQ_DISSERT.pdf: 1009487 bytes, checksum: af0c16848a5883b1c5e6bb465ced353e (MD5) Previous issue date: 2011-08-19 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This dissertation aims the development of an experimental device to determine quantitatively the content of benzene, toluene and xylenes (BTX) in the atmosphere. BTX are extremely volatile solvents, and therefore play an important role in atmospheric chemistry, being precursors in the tropospheric ozone formation. In this work a BTX new standard gas was produced in nitrogen for stagnant systems. The aim of this dissertation is to develop a new method, simple and cheaper, to quantify and monitor BTX in air using solid phase microextraction/ gas chromatography/mass spectrometry (SPME/CG/MS). The features of the calibration method proposed are presented in this dissertation. SPME sampling was carried out under non-equilibrium conditions using a Carboxen/PDMS fiber exposed for 10 min standard gas mixtures. It is observed that the main parameters that affect the extraction process are sampling time and concentration. The results of the BTX multicomponent system studied have shown a linear and a nonlinear range. In the non-linear range, it is remarkable the effect of competition by selective adsorption with the following affinity order p-xylene > toluene > benzene. This behavior represents a limitation of the method, however being in accordance with the literature. Furthermore, this behavior does not prevent the application of the technique out of the non-linear region to quantify the BTX contents in the atmosphere. / Esta disserta??o de mestrado trata da montagem e da valida??o de um dispositivo experimental para determinar quantitativamente os teores de benzeno, tolueno e xilenos (BTX) na atmosfera. BTX s?o solventes extremamente vol?teis e, portanto, desempenha um papel importante na qu?mica atmosf?rica, sendo precursores na forma??o de oz?nio troposf?rico. Nesta disserta??o um novo padr?o gasoso de BTX foi produzido em nitrog?nio para sistemas estagnados. O objetivo deste trabalho foi desenvolver um novo m?todo, simples e barato, para quantificar e monitorar BTX no ar utilizando microextra??o em fase s?lida, cromatografia gasosa/espectrometria de massa (SPME/CG/MS). As caracter?sticas do m?todo de calibra??o proposto s?o apresentadas nesta disserta??o. Amostragem SPME foi realizada sob condi??es de n?o-equil?brio usando uma fibra Carboxen / PDMS exposta por 10 minutos na mistura de gases padr?o BTX-N2. Observam que os principais par?metros que afetam o processo de extra??o s?o tempo de amostragem, concentra??o e temperatura. Os resultados do sistema multicomponente BTX-N2 estudado mostraram um comportamento linear e n?o-linear em termos de concentra??o de BTX. Na faixa n?o-linear, ? not?vel o efeito da concorr?ncia por adsor??o seletiva com a seguinte ordem de afinidade: p-xileno> tolueno> benzeno. Este comportamento representa uma limita??o do m?todo, no entanto, est? de acordo com a literatura e n?o impede a aplica??o da t?cnica fora da regi?o n?o linear para quantificar os teores de BTX na atmosfera.

BTX biodegradation rates, biochemical expression patterns and microbial ecology were studied under anoxic (denitrifying), anoxic/microaerobic/aerobic, and anoxic/microaerobic conditions in activated sludge sequencing batch reactors. The studies showed that toluene and m-xylene were denitrified via benzoyl-CoA reductase. Although benzene, o-, and p-xylene were recalcitrant under denitrifying conditions, they were biodegraded under microaerobic (< 0.2 mg/L dissolved oxygen) and nitrate or nitrite (NOx)-supplemented microaerobic conditions. The patterns of the specific enzymes associated with BTX biodegradation under microaerobic conditions indicated that the three compounds were metabolized by oxygen-dependent pathways. The expression levels of catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase under microaerobic conditions were induced to levels as high as under aerobic conditions (> 4 mg/L dissolved oxygen). Benzene, o-, and p-xylene biodegradation rates were twice as fast under NO_x-supplemented compared to NO_x-free microaerobic conditions, and the specific biodegradation rates under aerobic and NO_x-supplemented microaerobic conditions were comparable. 16S rRNA probes targeting representative toluene-degraders were used to investigate the microbial communities in the three sequencing batch reactors by using a dot blot hybridization technique. The hybridization results suggest that multiple redox environments fostered a more diverse microbial community and the activities of the target organisms in the reactors with multiple redox environments were higher than in the single redox reactor. Additionally, facultative toluene-degraders appeared to play a less significant role than the strict anoxic and aerobic toluene-degraders in all three SBRs. / Ph. D.

Es wurden Versuche für die ungesättigte Zone duchgeführt, um das Verhalten kleinerer Einträge an Benzen, Toluen und Xylen im Oberboden anschätzen zu können. In einem Vorversuch wurde der Verteilungskoeffizient Gas-Wasser für verschiedene Wässer bestimmt. Der Einfluss der Temperatur hatte einen größeren Einfluss als der Chemismus des Wassers. Die Sorption wurde ermittelt und zeigte sich als ein über sechs Größenordnungen linearer Prozess. Sie ist abhängig vom Humusgehalt. Versuche zur Desorption zeigen Unterschiede zwischen den Aromaten. Xylen desorbiert am langsamsten. Fünf, z.T. mehrmonatige Versuche mit einem großen Laborlysimeter (60 cm Durchmesser, 2 m Länge) zeigten, dass die Korngröße die Diffusion und dichtebedingte Konvektion der gasförmigen Aromaten beeinflusst. Diese Vorgänge sind für den schnellen Transport verantwortlich. Das Sickerwasser bewegt sich deutlich langsamer, transportiert aber die größeren BTX-Mengen. Humushaltige Böden können den Transport in tiefere Bereiche aufgrund von Sorption deutlich reduzieren. Mikrobieller Abbau lässt sich über den Sauerstoffverbrauch nachweisen.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-04-26T19:29:13Z No. of bitstreams: 1 DiogoRosemberghDaSilvaNobrega_DISSERT.pdf: 3407619 bytes, checksum: a00b7d07c5d402e8c57a1d3b73198713 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-04-28T23:50:33Z (GMT) No. of bitstreams: 1 DiogoRosemberghDaSilvaNobrega_DISSERT.pdf: 3407619 bytes, checksum: a00b7d07c5d402e8c57a1d3b73198713 (MD5) / Made available in DSpace on 2016-04-28T23:50:33Z (GMT). No. of bitstreams: 1 DiogoRosemberghDaSilvaNobrega_DISSERT.pdf: 3407619 bytes, checksum: a00b7d07c5d402e8c57a1d3b73198713 (MD5) Previous issue date: 2015-03-05 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Na ind?stria do petr?leo, a ?gua produzida ? o maior volume l?quido produzido com grande capacidade poluidora. Dentre os contaminantes org?nicos, os arom?ticos apresentam o principal risco ao meio ambiente e ? sa?de da popula??o principalmente BTEX. Ao longo dos ?ltimos anos, a eletroqu?mica tem se mostrado eficiente na degrada??o desses compostos, envolvendo apenas a utiliza??o de el?trons como reagentes. Entretanto, o desenho do reator eletroqu?mico, hidrodin?mica e, consequentemente, o coeficiente de transfer?ncia de massa s?o par?metros determinantes na efici?ncia do processo eletroqu?mico. Dentro desse contexto, o objetivo deste trabalho foi investigar geometrias de c?lulas eletroqu?micas, visando determinar os coeficientes de transfer?ncia de massa e entender a sua hidrodin?mica. Foram estudadas c?lulas em batelada e em fluxo, variando a pot?ncia da agita??o, posi??o da agita??o e espa?amento entre os eletrodos, empregando a t?cnica de corrente limite, com um gradiente de concentra??o de 4 a 24 mmol/dm? de K4[Fe(CN)]6 em propor??o molar de 2:1 para K3[Fe(CN)]6 em meio de NaOH 0,5 mol/dm?, a fim de determinar a corrente limite, e consequentemente o coeficiente de transfer?ncia de massa (km). Os resultados obtidos mostraram claramente que na c?lula em batelada, o aumento da agita??o e a posi??o da agita??o influenciaram o km; na c?lula em fluxo, o afastamento dos eletrodos n?o mostra influencia significativa quando a agita??o (fluxo) ? direcionada ? superf?cie do eletrodo; e ainda, as c?lulas em fluxo se mostraram mais eficientes no que diz respeito ? elimina??o de resist?ncias f?sicas inerentes ao tratamento eletro-oxidativo. Por fim, os resultados alcan?ados mostraram que ? poss?vel a aplica??o do reator eletroqu?mico no tratamento de BTX, uma vez que foi identificada uma geometria com o melhor coeficiente de massa, favorecendo a oxida??o das esp?cies na superf?cie do eletrodo, de forma mais r?pida e eficiente. / The oil and gas production processes generate large volumes of waste with high toxicity. In this industry, produced water is the most produced liquid volume with great polluting capacity. Among the organic contaminants, the aromatics, mainly BTEX, present a major risk to the environment and people's health. Over the past years, many studies have been conducted under the electrooxidation of aromatic compounds, showing that the electrochemical degradation is efficient for these substances, even more importantly, the process involves only the use of electrons as reactants. However, the design of the electrochemical reactor, hydrodynamics and mass transfer coefficients are critical parameters on the efficiency of the electrochemical process. In this context, the objective of this study was to investigate geometries of electrochemical cells, to determine the mass transfer coefficients and understand their hydrodynamics. Cells were studied in batch and flow design, varying stirring rate, the stirring position and spacing between electrodes. In order to determine the current limit, and thus the mass transfer coefficient (Km), it was used a concentration gradient of K4[FeCN]6 / K3[FeCN]6 (2:1) from 4 to 24 mM, in medium of 0.5 M NaOH. The results clearly showed that regarding the batch cell, increasing stirring rate and changing its position promote a considerable effect on Km; in the flow cell, no influences were achieved when the spacing of the electrodes was modified when the stirring (flow) is directed to the electrode surface; and, the flow cells are more efficient with regard to the elimination of inherent physical resistance to the electrochemical treatment. Finally, the results showed that the application of reactor is possible to treat electrochemically BTX because the better geometry has been identified, favoring the oxidation of the species on the electrode surface more rapidly and efficiently.