Palladium based catalysts are widely used for C-C bonding reactions. This work describes the preparation of several such catalysts deposited onto siliceous, SBA-15 type support and common silica gel, whose surface was modified by organic chains with amine donor groups. The prepared catalysts have been tested in coupling reactions of organotin compounds and organic halides (Stille reactions) under various conditions.

An evaluation of several commercial adsorbents for use as contacting media in a process for combustion gas desulfurization was performed. Linde Synthetic Molecular Sieves types 13X and AW500 and Davison Silica Gel were the materials studied. The motivation for this investigation was based on the premise that a suitable method for removing sulfur dioxide from combustion gas streams has not been realized. Sulfur dioxide adsorption capacities were obtained for equilibrium (non-flow) and dynamic flow conditions. Sulfur dioxide adsorption on the molecular sieves could be described by a modified Langmuir expression of the form q/q_m = kc^1/n/ 1 + kc^1/n Calculated isosteric heats of adsorption were found to agree with measured data. Small scale dynamic studies consisted of contacting the adsorbents in a packed column with a simulated combustion gas. Evaluation of the adsorbent materials consisted of monitoring the effluent gas concentration after exposure to a step change in sulfur dioxide concentration. Sulfur dioxide loadings were greatest for the type 13X molecular sieve followed by AW500 molecular sieve. The effect of gas throughput was minimal which suggests that mass transfer was adsorbent side controlling. As gas temperature increased, sulfur dioxide adsorption decreased linearly for 100 percent sulfur dioxide concentration and non-linearly for low concentrations (0.003 percent). The effect of water vapor on sulfur dioxide adsorption capacity was determined by monitoring the effluent gas composition for specified sulfur dioxide-water vapor mixtures. Breakthrough time for sulfur dioxide was found to be an inverse function of the inlet water vapor concentration. For a typical combustion gas stream, (8 percent water vapor) the breakthrough time is roughly 10 percent of the water vapor free value. Based on the results obtained, a shallow bed (0.15m, 0.5 ft) of either type 13X or AW500 molecular sieve removed 5 to 3 times that of activated charcoal for a gas temperature of 57.2°C (135°F) and low gas pressure drop 4.6 cm H₂0 (1.85 in. H₂0). Adsorption degradation studies were performed to determine the loss in sulfur dioxide adsorption capacity after adsorbent regeneration. Both the 13X and AW500 molecular sieve could be regenerated, but the loss in adsorption capacity depended on the gas contacting conditions. X-ray spectroscopy was used to determine the homogeneity of the sulfur distribution within the adsorbents. The sulfur dioxide adsorption capacity for subsequent regeneration cycles was found to be a function of the Al₂O₃/SiO₂ ratio of the molecular sieve. Application of the molecular sieve adsorbents in a simulated combustion gas for sulfur dioxide removal was found to be superior to several adsorbents for the temperature range 21-76°C (70-170°F). However, as gas temperature increases, sulfur dioxide adsorption decreases. No adsorption of sulfur dioxide above 148°C (300°F) could be measured. / Ph. D.

Made available in DSpace on 2014-12-17T15:42:29Z (GMT). No. of bitstreams: 1 MarcelaNB_TESE.pdf: 4650032 bytes, checksum: 4b8ec547749f785718e5f099093fa925 (MD5) Previous issue date: 2013-09-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Intensive use of machinery and engines burning fuel dumps into the atmosphere huge amounts of carbon dioxide (CO2), causing the intensification of the greenhouse effect. Climate changes that are occurring in the world are directly related to emissions of greenhouse gases, mainly CO2, gases, mainly due to the excessive use of fossil fuels. The search for new technologies to minimize the environmental impacts of this phenomenon has been investigated. Sequestration of CO2 is one of the alternatives that can help minimize greenhouse gas emissions. The CO2 can be captured by the post-combustion technology, by adsorption using adsorbents selective for this purpose. With this objective, were synthesized by hydrothermal method at 100 ?C, the type mesoporous materials MCM - 41 and SBA-15. After the synthesis, the materials were submitted to a calcination step and subsequently functionalized with different amines (APTES, MEA, DEA and PEI) through reflux method. The samples functionalized with amines were tested for adsorption of CO2 in order to evaluate their adsorption capacities as well, were subjected to various analyzes of characterization in order to assess the efficiency of the method used for functionalization with amines. The physic-chemical techniques were used: X- ray diffraction (XRD), nitrogen adsorption and desorption (BET/BJH), scanning electron microscopy (SEM), transmission electron microscopy (TEM), CNH Analysis, Thermogravimetry (TG/DTG) and photoelectron spectroscopy X-ray (XPS). The CO2 adsorption experiments were carried out under the following conditions: 100 mg of adsorbent, at 25 ?C under a flow of 100 ml/min of CO2, atmospheric pressure and the adsorption variation in time 10-210 min. The X-ray diffraction with the transmission electron micrographs for the samples synthesized and functionalized, MCM-41 and SBA-15 showed characteristic peaks of hexagonal mesoporous structure formation, showing the structure thereof was obtained. The method used was efficient reflux according to XPS and elemental analysis, which showed the presence of amines in the starting materials. The functionalized SBA -15 samples were those that had potential as best adsorbent for CO2 capture when compared with samples of MCM-41, obtaining the maximum adsorption capacity for SBA-15-P sample / A intensa utiliza??o de m?quinas e motores queimando combust?veis despeja na atmosfera imensas quantidades de di?xido de carbono (CO2), causando a intensifica??o do Efeito Estufa. As mudan?as clim?ticas que v?m ocorrendo no mundo est?o diretamente relacionadas ?s emiss?es de gases de efeito estufa, principalmente CO2, devido, sobretudo, ao uso excessivo de combust?veis f?sseis. A busca por novas tecnologias para minimizar os impactos ambientais decorrentes deste fen?meno vem sendo investigadas. O sequestro de CO2 ? uma das alternativas que pode ajudar a minimizar as emiss?es desses gases. O CO2 pode ser capturado pela tecnologia p?s-combust?o, atrav?s do processo de adsor??o, utilizando adsorventes seletivos para este fim. Com este objetivo, foram sintetizados, pelo m?todo hidrot?rmico a 100?C, materiais mesoporosos do tipo MCM-41 e SBA-15. Ap?s as s?nteses os materiais foram submetidos ? etapa de calcina??o e, posteriormente, funcionalizados com diferentes tipos de aminas (APTES, MEA, DEA e PEI), atrav?s do m?todo de refluxo. As amostras funcionalizadas com as aminas foram testadas nos ensaios de adsor??o de CO2 afim de avaliar suas capacidades de adsor??o, bem como, foram submetidas a diversas an?lises de caracteriza??o no intuito de avaliar a efici?ncia do m?todo utilizado para a funcionaliza??o com as aminas. As t?cnicas f?sico-qu?micas utilizadas foram: Difra??o de Raios-X (DRX), Adsor??o e Dessor??o de nitrog?nio (BET/BJH), Microscopia eletr?nica de varredura (MEV), Microscopia eletr?nica de transmiss?o (MET), An?lise elementar CNH, Termogravimetria (TG/DTG) e Espectroscopia fotoeletr?nica de Raios-X (XPS). Os ensaios de adsor??o de CO2 foram realizados nas seguintes condi??es: 100 mg de adsorvente, temperatura de 25 ?C sob fluxo de 100 mL/min de CO2, press?o atmosf?rica e com varia??o no tempo de adsor??o de 10 a 210 min. Os difratogramas de Raios-X juntamente com as micrografias eletr?nicas de transmiss?o para as amostras sintetizadas e funcionalizadas, MCM-41 e SBA-15, apresentaram os picos caracter?sticos da forma??o de estrutura mesoporosa hexagonal, evidenciando que a estrutura do mesmo foi obtida. O m?todo de refluxo utilizado foi eficiente segundo as an?lises de elementar e XPS, na qual, mostrou a presen?a das aminas nos materiais de partida. As amostras funcionalizadas de SBA-15 foram as que tiveram melhor potencial como adsorvente para captura de CO2 quando comparadas com as amostras de MCM-41, obtendo a m?xima capacidade de adsor??o para a amostra SBA-15-P

The current work focused on defining the material science options to fabricate novel, high performing ethylene/ethane (C₂H₄/C₂H₆) separation carbon molecular sieve (CMS) dense film membranes. Three polymer precursors: Matrimid®, 6FDA-DAM and 6FDA:BPDA-DAM were used as precursors to the CMS membranes. CMS performances were tailored by way of tuning pyrolysis conditions such as the pyrolysis temperature, heating rate, pyrolysis atmosphere etc. The CMS dense film membranes showed attractive C₂H₄/C₂H₆ separation performance far exceeding the polymeric membrane performances. Semi-quantitative diffusion size pore distributions were constructed by studying the transport performance of a range of different penetrant gases as molecular sized probes of the CMS pore structure. This, in conjunction with separation performance data, provided critical insights into the structure-performance relationships of the CMS materials. The effects of testing conditions, i.e. the testing temperature, pressure and feed composition on C₂H₄/C₂H₆ separation performance of CMS dense films were also analyzed. These studies were useful not just in predicting the membrane behavior from a practical stand-point, but also in a fundamental understanding of the nature of CMS membrane separation. The study helped clarify why CMS membranes outperform polymeric membrane performance, as well as allowed comparison between CMS derived from different precursors and processing conditions. The effects on C₂H₄/C₂H₆ separation in the presence of binary gas mixture were also assessed to get a more realistic measure of the CMS performance resulting from competition and bulk flow effects. The current work thus establishes a framework for guiding research ultimately aimed at providing a convenient, potentially scalable hollow fiber membrane formation technology for C₂H₄/C₂H₆ separation

Olefin/paraffin separation is a large potential market for membrane applications. Carbon molecular sieve membranes (CMS) are promising for this application due to the intrinsically high separation performance and the viability for practical scale-up. Intrinsically high separation performance of CMS membranes for olefin/paraffin separations was demonstrated. The translation of intrinsic CMS transport properties into the hollow fiber configuration is considered in detail. Substructure collapse of asymmetric hollow fibers was found during Matrimidﾮ CMS hollow fiber formation. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM polyimides with higher rigidity were employed as alternative precursors, and significant improvement has been achieved. Besides the macroscopic morphology control of asymmetric hollow fibers, the micro-structure was tuned by optimizing pyrolysis temperature protocol and pyrolysis atmosphere. In addition, unexpected physical aging was observed in CMS membranes, which is analogous to the aging phenomenon in glassy polymers. For performance evaluation, multiple "proof-of-concept" tests validated the viability of CMS membranes under realistic conditions. The scope of this work was expanded from binary ethylene/ethane and propylene/propane separations for the debottlenecking purpose to mixed carbon number hydrocarbon processing. CMS membranes were found to be olefins-selective over corresponding paraffins; moreover, CMS membranes are able to effectively fractionate the complex cracked gas stream in a preferable way. Reconfiguration of the hydrocarbon processing in ethylene plants is possible based on the unique CMS membranes.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-04-30T16:37:00Z No. of bitstreams: 1 CLÁUDIA DOURADO MEDEIROS - DISSERTAÇÃO PPGEQ 2014..pdf: 1542895 bytes, checksum: 5a74f0ba9e6514c2859c363f528e0b6f (MD5) / Made available in DSpace on 2018-04-30T16:37:00Z (GMT). No. of bitstreams: 1 CLÁUDIA DOURADO MEDEIROS - DISSERTAÇÃO PPGEQ 2014..pdf: 1542895 bytes, checksum: 5a74f0ba9e6514c2859c363f528e0b6f (MD5) Previous issue date: 2014-04-02 / Capes / As peneiras moleculares mesoporosas possuem um arranjo hexagonal de mesoporos com diâmetros de poros que variam de 2 a 10 nm, possuindo assim uma área superficial elevada. A adição de um metal a sua estrutura tem como função gerar a acidez ao material o tornando mais reativo, aumentado assim a possibilidade do seu uso como catalisador na indústria do petróleo. Atualmente, um dos problemas encontrados pelos pesquisadores para obtenção desse tipo de peneira, é o longo tempo de formação das estruturas. No presente trabalho as peneiras moleculares mesoporosas MCM-41 e Al-MCM-41 foram sintetizadas utilizando dois processos hidrotermais, a tradicional e por micro-ondas, com o objetivo principal de reduzir o tempo de síntese do material. A peneira molecular MCM-41 foi sintetizada utilizando o processo hidrotermal tradicional, 100 oC por 48 horas , como também utilizando o processo hidrotermal de micro-ondas através de três metodologias, adotando diferentes tempos e temperaturas. Tomando como base os resultados obtidos com as sínteses da peneira molecular MCM-41 por meio do método hidrotermal de micro-ondas, os mesmos métodos foram aplicados para a peneira molecular Al-MCM-41 nas mesmas condições de tempo e temperatura. Através dos difratogramas foi possível perceber que a estrutura hexagonal foi formada. Verificouse que o melhor tempo de síntese da Al-MCM-41 se deu com 60 minutos a 130 oC. A partir destes dados, foram realizadas novas sínteses, reduzindo o tempo gradativamente. Os resultados das análises de DRX, MEV e FTIR comprovam que as peneiras moleculares mesoporosas foram formadas, sendo possível identificar sua estrutura e morfologia. Os melhores resultados de síntese para as peneiras moleculares mesoporosas MCM-41 e Al-MCM-41, foram nos tempos 60 e 40 minutos e temperatura de 130 oC, respectivamente. / The mesoporous molecular sieves have a hexagonal arrangement of mesopores with pore diameters ranging from 2 to 10 nm, which implies in a high surface area. The addition of a metal into these structures has the function of generating acidity in the material making it more reactive, increasing the possibility of using it as a catalyst into the oil industry. Nowadays, one of the problems found by researches to obtain these type of molecular sieves is the long time of structure formation taken by these materials. In this study, the mesoporous molecular sieves MCM - 41 and Al -MCM -41 were synthesized using two traditional microwave, with the primary goal of reducing the time of synthesis of the material hydrothermal processes. The molecular sieve MCM -41 was synthesized using the traditional hydrothermal process 100 °C for 48 hours , as well as hydrothermal process using microwave by three methods , adopting different times and temperatures . Based on the results obtained with the synthesis of molecular sieve MCM -41 by hydrothermal microwave method, the same methods were applied to the molecular sieve Al -MCM -41 under the same conditions of time and temperature. Through the DRX patterns was observed that the hexagonal structure was formed. It was found that the best time of synthesis of Al- MCM-41 was given 60 minutes at 130 oC. From these data, new syntheses were carried out by reducing the time gradually. The results of DRX, MEV and FTIR show that the mesoporous molecular sieves were formed, it is possible to identify their structure and morphology. The best results for the synthesis of mesoporous molecular sieves MCM - 41 and Al -MCM -41, were at times 60 and 40 minutes and temperatures of 130 °C, respectively.

This thesis combines synthetic studies for isotopic enrichment with solid-state characterisation techniques to investigate two classes of microporous materials: zeolites and metal-organic frameworks (MOFs). These materials have a wide range of successful applications, from industrial catalysis to medicine, resulting in the increasing need for both a complete understanding of their unique structural features and synthetic methods to target new frameworks. Nuclear magnetic resonance (NMR) spectroscopy, thanks to its sensitivity to the local, atomic-scale, environment and its element specificity, is applied, in combination with powder X-ray diffraction (PXRD), electron microscopy, N2 adsorption and mass spectrometry, to the study of these materials. Oxygen atoms play a crucial role in the structure and chemistry of zeolites and MOFs, making 17O NMR an excellent tool for chemical and structural investigations. However, the low natural abundance of this isotope (0.037%) and the cost of 17O-enriched reactants require the development of atom-efficient synthetic processes for isotopic enrichment. In the first part of this work, the unconventional assembly-disassembly-organisation-reassembly (ADOR) method is applied to the Ge-doped UTL framework and optimised in reduced-volume conditions for economic enrichment to obtain 17O- and 29Si-enriched UTL-derived zeolites. In situ and ex situ solid-state characterisation studies show that isotopic enrichment not only enables a more detailed spectroscopic investigation, but also provides new insights into the mechanism of the ADOR process and its sensitivity to experimental conditions. In the second part of this work, dry gel conversion synthesis and a novel steaming procedure are studied as cost-effective 17O-enrichment pathways for Al, Ga and Sc mixed-metal terephthalate MOFs. 17O solid-state NMR spectroscopy, in combination with PXRD and electron microscopy, is employed to investigate cation disorder and 17O NMR spectra are shown to be sensitive to substitution of metal centers and conformational changes upon interaction with guest molecules.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The significant increase of carbon dioxide emissions in the atmosphere comes intensifying the global warming. The search for energetic source that turn emission down is of great importance, as well as the use of complementary actions like dioxide carbon capture process of the main emissions sources. From among some processes already very well-known industrially highlights chemical absorption with alkanolamine, which shows some disadvantages in being costly and generate waste derived from recovery. The use gas-solid selective in carbon dioxide adsorption has very advantages over absorption liquid amine such as easy handling without risks to the environment and recovering of adsorbent material, being possible to use industries plants with continuous flux. In this context were synthesized through hydrothermal method two materials of family M41S of type MCM-41 and MCM-48. Then the materials were impregnated with ethylenediamine by wet impregnation method. These materials were used for the carbon dioxide adsorption process and were characterized by several physic-chemical techniques. The powder X-ray diffraction patterns of the samples showed all peaks characteristics of MCM-41 and MCM-48 before and after impregnation with amines. The absorption spectrum in the infrared region showed bands due to Si-O and O-Si-O bonds in all materials and N-H bonds due to presence of amine in the supports after impregnation process. The thermogravimetric curves showed that stability of material containing amines is up to 100 °C. The materials showed N2 adsorption isotherms type IV, some with hysteresis type H1 and high surfaces areas (over 1000 m2 g-1). Carbon dioxide capture tests in flux system and atmosphere pressure showed significant drawbacks in the capture capacities of carbon dioxide for the materials impregnated with ethylenediamine in comparison to the values obtained with the MCM-41 and MCM-48 supports alone. Tests with closed system and pressure variation in the range of 0.5 to 30 bar allowed the construction of the isotherms to prepared materials of which were fitted using the Langmuir model. The results showed that the samples of MCM-41 and MCM-48 without impregnation are favorable for applications where high pressures are required. / O aumento significativo das emissões de dióxido de carbono na atmosfera vem acentuando o efeito do aquecimento global. A busca por fontes energéticas que minimizem as emissões é de grande importância, como também o uso de ações complementares como processos para captura deste gás das principais fontes emissoras. Dentre alguns processos já bem conhecidos industrialmente, destaca-se a absorção química com alcanolaminas, a qual apresenta algumas desvantagens por ser dispendiosa e gerar rejeitos da sua recuperação. O uso da adsorção gás-sólido seletiva de dióxido de carbono tem muitas vantagens sobre a absorção com aminas líquidas, tais como: fácil manipulação sem riscos ao ambiente, e recuperação do material adsorvente, podendo-se utilizar plantas industriais com fluxo contínuo. Neste contexto, foram sintetizados através do método hidrotérmico dois materiais da família M41S do tipo MCM-41 e MCM-48. Em seguida os materiais foram impregnados com etilenodiamina, através do método de impregnação por via úmida. Estes materiais foram utilizados para o processo de adsorção de dióxido de carbono e foram caracterizados por diversas técnicas físico-químicas. Os difratogramas de raios-X das amostras sintetizadas apresentaram os picos característicos do MCM-41 e do MCM-48 antes e após a impregnação com aminas. Os espectros de absorção na região do infravermelho mostraram bandas devido às ligações Si-O e O-Si-O em todos os materiais e de ligações N-H devido à presença da amina nos suportes após a impregnação. As curvas termogravimétricas mostraram que a estabilidade do material contendo aminas é de até 100 °C. Todos os materiais apresentaram isotermas de adsorção de N2 do tipo IV, alguns com histerese do tipo H1 e elevadas áreas superficiais (acima de 1000 m2 g-1). Os testes de captura de dióxido de carbono em sistema com fluxo e pressão atmosférica mostraram significativas reduções nas capacidades de captura para os materiais impregnados em comparação com os valores obtidos com os suportes MCM-41 e MCM-48. Testes com sistema fechado e variação de pressão na faixa de 0,5-30 bar permitiram o levantamento de isotermas de equilíbrio para os materiais preparados as quais foram ajustadas através do modelo de Langmuir. Os resultados mostraram que as amostras de MCM-41 e MCM-48 são favoráveis para aplicações onde altas pressões são requeridas.

The study of adsorption of n-alkanes in zeolite pores represents both a fundamental problem in molecular thermodynamics and also a problem with substantial industrial importance. Until mid 19th century, adsorption was mainly used for purification processes such as removal of H2S and mercaptans from natural gas and organic matter from water. However, with the emergence of molecular sieves, especially zeolites, adsorption processes have become an attractive alter- native to distillation in large scale separation of mixtures that have low relative volatility into streams each enriched in one of the components. The pore di- ameters of molecular sieves are of the order of molecular diameters and hence selective adsorption can be achieved by both a difference in adsorbate-adsorbent interactions of various species and obstruction by the pore walls to some of the species in the mixture. The existing adsorption theories such as Henry’s law, Langmuir adsorption model and BET isotherm are incapable of predicting the adsorption isotherms of n-alkanes in zeolite pores. The reason is that in microporous adsorbents, the sorbate molecular mechanisms are influenced by geometrical constraints also. This limitation in the use of theory can be overcome by developing a molecular model and using computers to mimic the real system. This nature of simulation is called molecular simulations. With the development of advanced algorithms, improved force-field parameters and very high computational power of present day computers, molecular simulations have become an important tool in studying adsorption on micro-porous materials. Adsorption experiments of mixtures of long chain alkanes into silicalite under liquid phase conditions show selectivity inversion and azeotrope formation. These effects are due to the subtle interplay between the size of the adsorbed molecules and pore topology of the adsorbent. The underlying molecular mechanisms responsible for selective uptake of one of the components cannot be obtained from experiments but can be realized through simulations. Therefore, in this study, the selective uptake of lighter component during liquid phase adsorption of C14/C15 and C15/C16 n-alkane binary mixtures in the zeolite silicalite is understood through configurational bias grand canonical Monte Carlo (CB- GCMC) molecular simulation technique and a course-grained siting analysis. The simulations are conducted under conditions of low and high loading. The siting pattern of the adsorbates inside the zeolite pores is used to explain the selectivity as seen in experiments.

No description available.