1 |
Optimisation de la texture poreuse des catalyseurs d'hydrocraquage / Optimisation of the porosity of hydrocracking catalystKenmogne Gatchuissi, Régine 01 July 2010 (has links)
L'objectif de cette thèse était d'étudier l'influence de la texture poreuse et de l'acidité des catalyseurs d'hydrocraquage, sur l'activité et la sélectivité en distillats moyens. Dans notre étude, nous avons envisagé deux approches : d'une part la préparation des catalyseurs à partir de la zéolithe Y à texture poreuse optimisée, et d'autre part à partir d'une silice mésoporeuse de type MCM-48. Dans la première approche, l'optimisation de la texture poreuse a été réalisée par un traitement post synthèse de dessilication d'une zéolithe Y commerciale (CBV760). Les propriétés physico-chimiques des matériaux résultants ont été évaluées par différentes techniques de caractérisation. L'évaluation de ces matériaux en hydrocraquage de molécules modèles montre une très nette amélioration de la sélectivité en coupe moyenne par rapport à un catalyseur de référence à texture poreuse non optimisée. Dans la seconde approche, nos efforts ont été dirigés vers l'optimisation de l'acidité des solides de type MCM-48. Pour cela une méthode de greffage post-synthèse d'alumine à la surface de ce solide a été envisagée, conduisant à l'obtention d'une acidité suffisante pour la réaction d'hydrocraquage. L'évaluation catalytique de ces matériaux montre qu'ils sont des catalyseurs performants en hydrocraquage et en hydroisomérisation / The objective of this thesis was to prepare hydrocracking catalysts for heavy feedstocks with improved selectivity into middle distillates. In this study we followed two strategies: on the one hand the preparation of catalysts based on a zeolite Y with enhanced porosity, and on the other hand using a mesostructured silica (MCM-48). In the first approach, the optimization of the porous texture was realized by desilication of zeolite Y ( CBV760) in alkaline medium. Physico-chemical properties of obtained materials were investigated by various characterization techniques. The evaluation of these materials in the hydrocracking of model molecules shows a clear improvement of the selectivity into middle distillate with regards catalysts. In the second approach, our efforts were oriented towards the optimization of the acidity of MCM-48 type materials. To achieve this goal, an alumina layer was grafted on the surface of this material, generating an adequate acidity for the hydrocracking reaction. The catalytic evaluation of these materials shows a high selectivity inti middle distillates.
|
2 |
Desenvolvimento de peneiras moleculares mesoporosas do tipo MCM-41 e MCM-48 impregnadas com aminas para utilização na adsorção de CO2 / DEVELOPMENT OF TYPE MESOPOROUS MOLECULAR SIEVES MCM-41 AND MCM-48 IMPREGNATED WITH AMINES FOR USE IN ADSORPTION CO2.Oliveira, Thiago Gallo de 25 July 2012 (has links)
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.
|
3 |
Modified mesoporous silica membranes for separation applicationsKim, Hyung Ju 27 August 2014 (has links)
The main theme of this dissertation is the fabrication and analysis of modified mesoporous silica membranes for separation applications. Synthesis methods for mesoporous silica membranes have been developed to enhance the transport performance and quality of the membranes, such as permeability, pore volume, and surface area. Then, synthesized membranes were modified with different organic groups to tailor selectivity in separations. The collected studies of modified mesoporous silica membranes showed that appropriate functionalization on newly synthesized novel membranes leads to promising structural and permeation properties. First, a seeded growth method was developed for synthesis of MCM-48 membranes on alumina supports, thereby extending the seeded growth technique used for zeolite membranes to mesoporous silica membrane synthesis. The surface properties of the MCM-48 membranes were then modified by silylation with hexamethyldisilazane (HMDS). In comparison to MCM-48 membranes previously synthesized by the in situ growth technique, much less silica infiltration into the alumina support was observed. The pore structure of the MCM-48 membranes demonstrated that a large accessible pore volume was available for molecular permeation and pore modification to tailor selectivity. The gas permeation properties of the calcined and silylated MCM-48 membranes were consistent with a Knudsen-like mechanism, albeit with a substantial influence of gas-solid interactions in the mesopores. The silylated MCM-48 membranes were evaluated for pervaporative separation of ethanol (EtOH), methyl ethyl ketone (MEK), and ethyl acetate (EA) from their dilute aqueous solutions. The synthesized membranes exhibited high pervaporative separation factors and organic fluxes. The selective separation of organic/water mixtures with MCM-48 membranes were attributed to both the organophilic nature of the surface and the effective pore size of the silylated mesopores. Next, the synthesis and organic/water separation properties of mesoporous silica membranes supported on low-cost and scalable polymeric (polyamide-imide) hollow fibers and modified by trimethylsilylation with HMDS was studied. Thin, defect-free membranes that exhibited high gas permeances consistent with Knudsen-like diffusion through the mesopores were prepared. Silylation of these membranes did not affect the integrity of the mesoporous silica structure and the underlying polymeric hollow fiber, but led to capping of the surface silanol groups in the mesopores with trimethylsilyl groups. The silylated mesoporous membranes were evaluated for pervaporative separation of EtOH, MEK, EA, iso-butanol, and n-butanol from their dilute aqueous solutions. The membranes showed higher separation factors than those of flat membranes, along with high organic fluxes. The large increase in hydrophobicity of the membranes upon silylation allowed upgrading of the feed mixtures to permeate streams with considerably higher organic content. The selective separation of organic/water mixtures with the fiber-supported mesoporous silica membranes was attributed to both the organophilic nature of the surface (yielding good adsorption selectivity) and the effective pore size of the silylated mesopores (giving good fluxes). Comparison with other types of organic/water separation membranes revealed that the present silylated membrane platform shows good promise for use in organic/water separation applications due to its high flux, scalable and low-cost fabrication methodology, and good separation factors that can be further enhanced by tailoring the mesopore modification chemistry. Further, the gas transport properties of aziridine-functionalized mesoporous silica membranes on polymeric hollow fibers have also investigated. The mesoporous membranes were amine-functionalized with aziridine and their transport properties were studied to understand the effects of surface functionalization on gas separations. This new hybrid aminosilica membrane showed interesting and counter-intuitive N₂ selective permeation properties in dry CO₂/N₂ separations. Detailed characterization of the membrane structure and its permeation behavior showed that such behavior was due to the strong adsorption of CO₂, leading to reduced gas flux because of CO₂-induced amine crosslinking in the mesopores. This hyper-branched aminosilica membrane showed CO₂ selective properties when applied to humid gas permeation. Water molecules in the humid gas affected the adsorption of CO₂ molecules by causing a lower degree of crosslinking, allowing facilitated transport of CO₂.
|
4 |
S?ntese e caracteriza??o de materiais mesoporosos para a captura de CO2: influ?ncia do ?xido de n?quel / Synthesis and characterization of mesoporous materials for CO2 capture: influence of nickel oxide. thesis of doctorateNascimento, Alexsandra Rodrigues do 23 September 2014 (has links)
Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-01-20T21:00:39Z
No. of bitstreams: 1
AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-01-21T20:23:04Z (GMT) No. of bitstreams: 1
AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5) / Made available in DSpace on 2016-01-21T20:23:04Z (GMT). No. of bitstreams: 1
AlexsandraRodriguesDoNascimento_TESE.pdf: 3128857 bytes, checksum: db683b893d3db23b5af91852c4aed0e3 (MD5)
Previous issue date: 2014-09-23 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Diversos materiais est?o atualmente em estudo para o processo de captura de CO2, a
exemplo dos ?xidos met?licos e ?xidos met?licos mistos, ze?litas, materiais carbon?ceos,
estruturas metal-org?nicas (MOF?s), organos?lica e superf?cies de s?lica modificadas. Neste
trabalho, analisou-se a capacidade de adsor??o de CO2 em materiais mesoporosos de
diferentes estruturas, como o MCM-48 e SBA-15, sem impregna??o e impregnados com
n?quel nas propor??es 5 %, 10 % e 20 % (m/m), denominados como 5Ni-MCM-48, 10NiMCM-48,
20Ni-MCM-48 e 5Ni-SBA-15, 10Ni-SBA-15, 20Ni-SBA-15. Os materiais foram
caracterizados atrav?s das an?lises de difra??o de raios X (DRX), an?lise t?rmica (TG e
DTG), espectroscopia na regi?o do infravermelho com transformada de Fourier (FT-IR),
adsor??o e dessor??o de N2 (BET) e microscopia eletr?nica de varredura (MEV) com EDS. O
processo de adsor??o foi realizado variando-se a press?o de 100 - 4000 kPa e mantendo-se a
temperatura constante e igual a 298 K. Na press?o de 100 kPa, as maiores concentra??es de
adsor??o ocorreram para os materiais 5Ni-MCM-48 (0,795 mmol g-1
) e SBA-15 (0,914 mmol
g
-1
) n?o impregnado, e, na press?o de 4000 kPa, para os materiais MCM-48 (14,89 mmol g-1
)
e SBA-15 (9,97 mmol g-1
) n?o impregnados. Os resultados mostraram que a capacidade de
adsor??o varia positivamente com a ?rea espec?fica, no entanto, apresenta uma depend?ncia
direta com o tipo e geometria dos canais da estrutura porosa. Os dados obtidos foram
ajustados atrav?s dos modelos de Langmuir e Freundlich e os par?metros termodin?micos
avaliados foram energia livre de Gibbs e entropia do sistema de adsor??o / Several materials are currently under study for the CO2 capture process, like the metal
oxides and mixed metal oxides, zeolites, carbonaceous materials, metal-organic frameworks
(MOF's) organosilica and modified silica surfaces. In this work, evaluated the adsorption
capacity of CO2 in mesoporous materials of different structures, such as MCM-48 and SBA-
15 without impregnating and impregnated with nickel in the proportions 5 %, 10 % and 20 %
(m/m), known as 5Ni-MCM-48, 10Ni-MCM-48, 20Ni-MCM-48 and 5Ni-SBA-15, 10NiSBA-15,
20Ni-SBA-15. The materials were characterized by means of X-ray diffraction
(XRD), thermal analysis (TG and DTG), Fourier transform infrared spectroscopy (FT-IR), N2
adsorption and desorption (BET) and scanning electron microscopy (SEM) with EDS. The
adsorption process was performed varying the pressure of 100 - 4000 kPa and keeping the
temperature constant and equal to 298 K. At a pressure of 100 kPa, higher concentrations of
adsorption occurred for the materials 5Ni-MCM-48 (0.795 mmol g-1
) and SBA-15 (0.914
mmol g-1
) is not impregnated, and at a pressure of 4000 kPa for MCM-48 materials (14.89
mmol g-1) and SBA-15 (9.97 mmol g-1) not impregnated. The results showed that the
adsorption capacity varies positively with the specific area, however, has a direct dependency
on the type and geometry of the porous structure of channels. The data were fitted using the
Langmuir and Freundlich models and were evaluated thermodynamic parameters Gibbs free
energy and entropy of the adsorption system
|
5 |
Síntese de materiais compósitos micro-mesoporosos visando a captura de CO2Silva, Silvia Caroline Gomes dos Santos 29 July 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / factor responsible for climate change worldwide. In recent years, several research are intended to developing new methods and technologies to capture and separation CO2.
The use of the adsorption method for separating CO2 is a promising alternative in view of the potential to reduce energy costs by eliminating aqueous solutions and providing capture and regeneration rates adequate. In this context, this paper presents the synthesis of composite type materials ZSM-12 / MCM-41 and ZSM-12 / MCM-48, seeking to combining the properties of the zeolitic material to the structural advantages of mesoporous materials, resulting in obtaining materials with high CO2 adsorption capacity. For this, the materials were synthesized by hydrothermal method and mechanosynthesis. The materials were characterized by XRD, absorption spectroscopy in the infrared, thermal analysis, adsorption-desorption analysis of N2 A 77 K, SEM and TEM. The CO2 adsorption capacity of these materials were investigated by gravimetric analysis. The results obtained from the characterization techniques showed that the synthesis methodology, used for desilication phase of ZSM-12, was efficient in obtaining a composite material with integrated micro and mesoporous phases. On the other hand, the results showed that by mechanosynthesis was possible to obtain materials formed by mixing between the micro and mesoporous phases. Also, comparing the results of adsorption CO2 the obtained composite materials by hydrothermal method with those obtained by mechanosynthesis it was concluded that the adsorption capacity is influenced by crystallinity and amount of the phase ZSM-12. The results showed from adsorption, in general, ZM48-75 samples, ZM41 A/MH R3 and ZM41-50 showed higher adsorption capacity than pure zeolitic and mesoporous materials, respectively. Thus, the composite materials of the type ZSM-12/ZSM-41 and MCM-12/MCM-48 are promising adsorbents for CO2 separation. / O aumento da concentração de dióxido de carbono na atmosfera é apontado como o principal fator responsável pelas mudanças climáticas em escala mundial. Nos últimos anos, várias pesquisas têm por finalidade o desenvolvimento de novos métodos e tecnologias para captura e separação de CO2. A utilização do método de adsorção para separação de CO2 é uma alternativa promissora, tendo em vista o potencial para reduzir os custos energéticos, eliminando soluções aquosas e proporcionando captura e taxa de regeneração adequadas. Nesse contexto, neste trabalho apresenta-se a síntese de materiais compósitos do tipo ZSM-12/MCM-41 e ZSM-12/MCM-48, visando combinar as propriedades do material zeolítico com as vantagens estruturais dos materiais mesoporosos, resultando na obtenção de materiais com elevadas capacidades de adsorção de CO2. Para isto, os materiais foram sintetizados pelo método hidrotérmico e por mecanosíntese. Os materiais obtidos foram caracterizados por DRX, espectroscopia de absorção na região do infravermelho, análise térmica, analise de adsorção-desorção de N2 A 77 K, MEV e TEM. A capacidade de adsorção de CO2 destes materiais foi investigadas através da análise gravimétrica. As técnicas de caracterização mostraram que a metodologia de síntese adotada via dessilicalização da fase ZSM-12 foi satisfatória na obtenção de um material compósito com as fases micro e mesoporosas integradas. Por outro lado, os resultados evidenciaram que através da mecanosíntese foi possível obter materiais formados pela mistura entre as fases micro e mesoporosas. Além disso, comparando-se os resultados de adsorção de CO2 dos materiais compósitos obtidos via método hidrotérmico com os obtidos via mecanosíntese foi possível concluir que a capacidade de adsorção é influenciada pela cristalinidade ou teor da fase ZSM-12. Considerando-se os resultados de adsorção apresentados, de maneira geral, as amostras ZM48-75, ZM41-A/R3-MH e ZM41-50, apresentaram maior capacidade de adsorção que os materiais zeolíticos e mesoporosos puros, respectivamente. Sendo assim, os materiais compósitos do tipo ZSM-12/MCM-41e ZSM-12/MCM-48 são promissores adsorventes para separação de CO2.
|
6 |
Síntese de materiais compósitos micro-mesoporosos visando a captura de CO2Silva, Silvia Caroline Gomes dos Santos 29 July 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / factor responsible for climate change worldwide. In recent years, several research are intended to developing new methods and technologies to capture and separation CO2.
The use of the adsorption method for separating CO2 is a promising alternative in view of the potential to reduce energy costs by eliminating aqueous solutions and providing capture and regeneration rates adequate. In this context, this paper presents the synthesis of composite type materials ZSM-12 / MCM-41 and ZSM-12 / MCM-48, seeking to combining the properties of the zeolitic material to the structural advantages of mesoporous materials, resulting in obtaining materials with high CO2 adsorption capacity. For this, the materials were synthesized by hydrothermal method and mechanosynthesis. The materials were characterized by XRD, absorption spectroscopy in the infrared, thermal analysis, adsorption-desorption analysis of N2 A 77 K, SEM and TEM. The CO2 adsorption capacity of these materials were investigated by gravimetric analysis. The results obtained from the characterization techniques showed that the synthesis methodology, used for desilication phase of ZSM-12, was efficient in obtaining a composite material with integrated micro and mesoporous phases. On the other hand, the results showed that by mechanosynthesis was possible to obtain materials formed by mixing between the micro and mesoporous phases. Also, comparing the results of adsorption CO2 the obtained composite materials by hydrothermal method with those obtained by mechanosynthesis it was concluded that the adsorption capacity is influenced by crystallinity and amount of the phase ZSM-12. The results showed from adsorption, in general, ZM48-75 samples, ZM41 A/MH R3 and ZM41-50 showed higher adsorption capacity than pure zeolitic and mesoporous materials, respectively. Thus, the composite materials of the type ZSM-12/ZSM-41 and MCM-12/MCM-48 are promising adsorbents for CO2 separation. / O aumento da concentração de dióxido de carbono na atmosfera é apontado como o principal fator responsável pelas mudanças climáticas em escala mundial. Nos últimos anos, várias pesquisas têm por finalidade o desenvolvimento de novos métodos e tecnologias para captura e separação de CO2. A utilização do método de adsorção para separação de CO2 é uma alternativa promissora, tendo em vista o potencial para reduzir os custos energéticos, eliminando soluções aquosas e proporcionando captura e taxa de regeneração adequadas. Nesse contexto, neste trabalho apresenta-se a síntese de materiais compósitos do tipo ZSM-12/MCM-41 e ZSM-12/MCM-48, visando combinar as propriedades do material zeolítico com as vantagens estruturais dos materiais mesoporosos, resultando na obtenção de materiais com elevadas capacidades de adsorção de CO2. Para isto, os materiais foram sintetizados pelo método hidrotérmico e por mecanosíntese. Os materiais obtidos foram caracterizados por DRX, espectroscopia de absorção na região do infravermelho, análise térmica, analise de adsorção-desorção de N2 A 77 K, MEV e TEM. A capacidade de adsorção de CO2 destes materiais foi investigadas através da análise gravimétrica. As técnicas de caracterização mostraram que a metodologia de síntese adotada via dessilicalização da fase ZSM-12 foi satisfatória na obtenção de um material compósito com as fases micro e mesoporosas integradas. Por outro lado, os resultados evidenciaram que através da mecanosíntese foi possível obter materiais formados pela mistura entre as fases micro e mesoporosas. Além disso, comparando-se os resultados de adsorção de CO2 dos materiais compósitos obtidos via método hidrotérmico com os obtidos via mecanosíntese foi possível concluir que a capacidade de adsorção é influenciada pela cristalinidade ou teor da fase ZSM-12. Considerando-se os resultados de adsorção apresentados, de maneira geral, as amostras ZM48-75, ZM41-A/R3-MH e ZM41-50, apresentaram maior capacidade de adsorção que os materiais zeolíticos e mesoporosos puros, respectivamente. Sendo assim, os materiais compósitos do tipo ZSM-12/MCM-41e ZSM-12/MCM-48 são promissores adsorventes para separação de CO2.
|
7 |
Synthesis and Characterization of Ordered Mesoporous Silica with Controlled Macroscopic Morphology for Membrane ApplicationsJanuary 2011 (has links)
abstract: Ordered mesoporous materials have tunable pore sizes between 2 and 50 nm and are characterized by ordered pore structures and high surface areas (~1000 m2/g). This makes them particularly favorable for a number of membrane applications such as protein separation, polymer extrusion, nanowire fabrication and membrane reactors. These membranes can be fabricated as top-layers on macroporous supports or as embedded membranes in a dense matrix. The first part of the work deals with the hydrothermal synthesis and water-vapor/oxygen separation properties of supported MCM-48 and a new Al-MCM-48 type membrane for potential use in air conditioning systems. Knudsen-type permeation is observed in these membranes. The combined effect of capillary condensation and the aluminosilicate matrix resulted in the highest separation factor (142) in Al-MCM-48 membranes, with a water vapor permeance of 6×10-8mol/m2Pas. The second part focuses on synthesis of embedded mesoporous silica membranes with helically ordered pores by a novel Counter Diffusion Self-Assembly (CDSA) method. This method is an extension of the interfacial synthesis method for fiber synthesis using tetrabutylorthosilicate (TBOS) and cetyltrimethylammonium bromide (CTAB) as the silica source and surfactant respectively. The initial part of this study determined the effect of TBOS height and humidity on fiber formation. From this study, the range of TBOS heights for best microscopic and macroscopic ordering were established. Next, the CDSA method was used to successfully synthesize membranes, which were characterized to have good support plugging and an ordered pore structure. Factors that influence membrane synthesis and plug microstructure were determined. SEM studies revealed the presence of gaps between the plugs and support pores, which occur due to shrinking of the plug on drying. Development of a novel liquid deposition method to seal these defects constituted the last part of this work. Post sealing, excess silica was removed by etching with hydrofluoric acid. Membrane quality was evaluated at each step using SEM and gas permeation measurements. After surfactant removal by liquid extraction, the membranes exhibited an O2 permeance of 1.65x10-6mol/m2.Pa.s and He/O2 selectivity of 3.30. The successful synthesis of this membrane is an exciting new development in the area of ordered mesoporous membrane technology. / Dissertation/Thesis / Ph.D. Chemical Engineering 2011
|
8 |
Synthesis, adsorption and structural properties of carbons with uniform and ordered mesoporesGierszal, Kamil Piotr 09 April 2008 (has links)
No description available.
|
9 |
Understanding and Modifying TiO<sub>2</sub> for Aqueous Organic PhotodegradationSun, Bo 26 September 2005 (has links)
No description available.
|
10 |
Photocatalysis studies using mesoporous modified V-MCM-48 Stober synthesis: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, & acetonitrileMahoney, Luther James January 1900 (has links)
Master of Science / Department of Chemistry / Kenneth J. Klabunde / Although Degussia-Huls P-25 TiO[subscript]2 semiconductor photocatalyst has high photodegradation rate for organic molecules, it works only under ultra-violet (UV) light. Mesoporous metal doped V-MCM-48 silica was synthesized under ambient conditions for use as a visible-light photocatalyst to convert toxic probe molecules to innocuous products: CO[subscript]2 + H[subscript]2O. The synthesis employed a modified Stober metal doped MCM-48 silica method. Powder X-ray diffraction (XRD), diffuse-reflectance-ultra-violet-visible (DR-UV-vis) spectroscopy, and N[subscript]2 adsorption-desorpton analysis characterization methods were completed on V-MCM-48 mesoporous material. These characterization methods indicate V-MCM-48 structure had formed with visible light absorption and mesoporous properties. Photocatalysis studies were completed with V-MCM-48 under dark, visible, and UV-light illumination conditions for the following probe molecules: acetaldehyde, carbon monoxide, ethanol, acetone, 2-propanol, and acetonitrile. Acetaldehyde over V-MCM-48 was converted to CO[subscript]2 under dark, visible, and UV-light conditions. Carbon monoxide photooxidation occurred over V-MCM-48 under visible and UV-light. Ethanol and acetonitrile had smaller photodegradation activity over V-MCM-48. Acetone and 2-propanol had no activity photocatalytically. Under dark and visible light illumination, V-MCM-48 consumed approximately one-half acetaldehyde and produced one-third CO[subscript]2 concentration as compared with the P-25 TiO[subscript]2 under UV-light. V-MCM-48 produced two-thirds of the amount of CO[subscript]2 in comparison to nanoparticle Au/ZnO catalyst under UV-light. The results infer V-MCM-48 might be useful in gas and liquid phase photocatalysis including water-splitting due to a high oxidation state (V[superscript]5+), visible light absorption, and high surface area. In conclusion, an extended literature review has been completed and literature employed extensively throughout the thesis with potential methods to further the research on V-MCM-48/Si-MCM-48 in catalysis, chromatography, adsorption/gas separation, and solar collection/water-splitting.
|
Page generated in 0.0267 seconds