Tesi sul tema "Membranes (Technology)"
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1
Sorensen, E. Todd. "Cross-linkable polyimide blends for stable membranes". Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/10086.
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Keuler, Johan Nico. "Preparation and characterisation of palladium composite membranes". Thesis, Link to the online version, 1997. http://hdl.handle.net/10019/1431.
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3
Bighane, Neha. "Novel silica membranes for high temeprature gas separations". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43732.
Testo completoAbstract (sommario):
Membrane materials for gas separations span a wide range including polymers, metals, ceramics and composites. Our aim is to create economical hydrothermally stable membranes that can provide high H₂-CO₂ separation at a temperature of 300 degree Celsius, for application in the water-gas shift reactor process. The present work describes the development of novel silica and silica-titania membranes from the controlled oxidative thermolysis of polydimethylsiloxane. The scope of this thesis is fabrication of membranes, material characterization and preliminary gas permeation tests (35-80 degree Celsius) on PDMS derived silica membrane films. The developed membranes can withstand up to 350 degree C in air. High permeabilties of small gas penetrants like He, H₂ and CO₂ have been observed and fairly high separation factors of O₂/N₂=3, H₂/N₂= 14 and H₂/CH₄=11 have been obtained. As the temperature of operation increases, the permeability of hydrogen increases and the separation factor of H₂ from CO₂ increases. The silica membranes exhibit gas separation factors higher than the respective Knudsen values. Additionally, design and construction of a new high temperature gas permeation testing system is described, which will cater to gas permeation tests at temperatures up to 300 degree Celsius for future work. The thesis also includes a detailed plan for future studies on this topic of research.
4
Keuler, Johan Nico. "Optimising catalyst and membrane performance and performing a fundamental analysis on the dehydrogenation of ethanol and 2-butanol in a catalytic membrane reactor". Thesis, Link to the online version, 2000. http://hdl.handle.net/10019.1/1277.
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5
Poletto, Patrícia. "Caracterização de membranas de poliamida 66 preparadas pelo método de inversão de fases". reponame:Repositório Institucional da UCS, 2010. https://repositorio.ucs.br/handle/11338/573.
Testo completoAbstract (sommario):
Neste trabalho foram preparadas membranas de poliamida 66 (PA 66) pelo método de inversão de fases (IF) e caracterizadas com o objetivo de verificar sua possível aplicação em processos de separação. As membranas de PA 66 foram preparadas utilizando dois solventes diferentes, ácido fórmico (AF) e ácido clorídrico (HCl) e água como não-solvente. As membranas preparadas na forma de filmes (não suportadas) foram caracterizadas por Espectroscopia de Infravermelho com Transformada de Fourier (FT-IR) e calorimetria exploratória diferencial (DSC), onde os resultados mostraram que a estrutura química e o comportamento térmico da PA 66 não foram alterados como o uso de ácidos como solventes. Os filmes apresentaram estrutura assimétrica, com formação de camada densa na parte superior seguida de subestrutura de poros esféricos observada por microscopia eletrônica de varredura (MEV). A espessura de camada densa variou de 10 à 25 μm, para o filme preparado em AF e HCl, respectivamente. O aumento da espessura da camada densa, ou seja, a redução de espaços vazios influenciou diretamente os resultados de percentual de água absorvida e porosidade total. A porosidade foi de 15 contra 50% para os filmes preparados em AF e HCl, respectivamente. O fluxo de vapor de água foi menor para os filmes com maior espessura de camada densa, devido ao aumento da resistência ao transporte de massa. Com o objetivo de aumentar a resistência mecânica dos filmes de poliamida, foram preparadas membranas suportadas em tecido de poliéster para posterior aplicação em processos de separação que utilizam altas pressões. As membranas suportadas foram caracterizadas pelas técnicas de BET para determinação de tamanho médio de poros, ensaios de osmose inversa (OI) e ultrafiltração (UF). Ambas as membranas preparadas em AF e HCl apresentaram valores de tamanho de poro muito próximos quando analisado por BET. O ensaio de compactação com água pura realizado a 40 bar de pressão revelou que as membranas preparadas em AF sofrem maior compactação na sua estrutura apresentando fluxo de permeado em torno de 22 Lm-2h-1 enquanto a membrana preparada em HCl apresentou fluxo de 312 Lm-2h-1. No ensaio de OI, a rejeição máxima ao cloreto de sódio foi de 7% e 4% para a membrana AF-3 e HCl-3, respectivamente. Nos ensaios de ultrafiltração (UF), realizados a 15 bar, ambas as membranas apresentaram valores de rejeição próximos a 70% para albumina de ovo e 80% para albumina bovina. Com esse resultado, podemos concluir que ambas as membranas apresentaram características de tamanho de poro e rejeição para aplicações em processos de UF.Submitted by Marcelo Teixeira (mvteixeira@ucs.br) on 2014-06-04T16:11:59Z No. of bitstreams: 1 Dissertacao Patricia Poletto.pdf: 15767648 bytes, checksum: 81ddada763fec9ceadc8f928e56747a6 (MD5)
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In the present study, polyamide 66 (PA 66) membranes were prepared by phase inversion (PI) and characterized in order to verify their potential application in separation processes. PA 66 membranes were prepared using two different solvents, formic acid (FA) and chloridric acid (HCl), and water as a non-solvent. Membranes prepared in film form (not supported) were characterized by Fourier-transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) and the results showed that the chemical structure and thermal behavior of the PA 66 were not altered by the use of acids as solvents. The films revealed an asymmetric structure with a dense top layer and a porous sublayer featuring spherical pores observed by scanning electron microscopy (SEM). The thickness of the dense layer varied from 10 to 25 μm in films prepared with FA and HCl, respectively. The increase in thickness of the dense layer, i.e., the reduction of empty spaces, directly influenced the results regarding water absorption percentage and total porosity. The porosity found was 15% and 50% for films prepared with FA and HCl, respectively. Water vapor flux was lower in films with a thicker dense layer as a result of a greater resistance to mass transfer. In order to increase mechanical resistance in polyamide films, supported membranes with polyester fabric were prepared for latter application in separation processes through high pressure. Supported membranes were characterized by BET techniques for the determination of pore size, reverse osmosis and ultrafiltration assays. Both membranes prepared with FA and HCl showed very similar pore sizes when analyzed by/with BET. A compression assay with pure water performed at a pressure of 40 bar revealed that membranes prepared with FA undergo greater compaction of its structure and had a permeate flux value of approximately 22 Lm-2h-1 whereas the membrane prepared with HCl had a permeate flux value of 312 Lm-2h-1. On reverse osmosis assays, the maximum rejection to sodium chloride was 7% and 4% for FA-3 and HCl-3 membranes, respectively. On ultrafiltration assays, performed at 15 bar, both membranes had rejection values close to 70% for egg albumin and 80% for bovine albumin. Based on this result, it is possible to conclude that both membranes revealed pore size and rejection characteristics for application in ultrafiltration processes.
6
Handelsman, Timothy David. "Membranes for Biorefineries". Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/14569.
Testo completoAbstract (sommario):
This thesis tested the hypothesis that whilst membranes may enable biorefineries to meet discharge specifications, such ‘end-of-pipe’ treatment options are sub-optimal. Greater savings can potentially be made by internal and/or upfront use of membranes. Biorefineries are used to make a wide range of products from substrates such as molasses, corn syrup and cellulosic materials, producing biofuels, pharmaceutical products and mass production of various microorganisms. These are generally produced at low concentrations, resulting in large amounts of wastewater. These wastewaters also contain high concentrations of recalcitrant organic compounds, which have high COD and dark colour. Membrane filtration has in the past typically been used as an ‘end-of-pipe’ treatment option, but can be employed to greater effect further upstream in the baker’s yeast production process. Utilising membrane technology to facilitate the recycling of water and salt from molasses wastewater proved to be successful and could also be used to recover water and other components from lignocellulosic wastewater. Melanoidins are recalcitrant organic macromolecules, which are mainly responsible for the dark brown colour in molasses. The presence of these coloured compounds in the fermentation produces a brown coloured yeast, requiring multiple washing stages to meet the market requirements of the yeast product, the majority of which is sold for the large scale production of sliced white bread. Membranes can be used to remove the bulk of this colour with minimal effect on the yeast’s yield and activity. This thesis has successfully demonstrated the potential of using membrane technologies internally and/or upfront in biorefinery processes, rather than in their customary role as ‘end-of-pipe’ treatment options for both the molasses fermentation industry and the cellulosic ethanol industry, suggesting that membrane technologies have the versatility to be applied across a range of biorefinery processes.
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McCool, Benjamin A. "Synthesis and Characterization of Microporous Silica Membranes Fabricated through Pore Size Reduction of Mesoporous Silica Membranes Using Catalyzed Atomic Layer Deposition". Fogler Library, University of Maine, 2004. http://www.library.umaine.edu/theses/pdf/McCoolBA2004.pdf.
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Borgsmiller, Karen McNeal. "Synthetic membranes for chiral separations". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/11824.
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Thrasher, Stacye Regina. "Polymeric membranes for organic vapor recovery". Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12358.
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Harper, Davnet. "Novel applications of membrane technology". Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248220.
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Medugno, Cláudia Conti. "Fases de membranas fluidas -L3 a partir de lipídio sintético e pentanol na região diluída - e o respectivo dialisado". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266692.
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Orientador: Elias Basile TambourgiTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: A fase L3 (esponja) foi observada no final dos anos 80 e representa uma nova classe de auto moldagem para sistemas surfactantes em água. Esse trabalho descreve a descoberta e a posterior caracterização de uma fase ternária composta do lipídio sintético catiônico brometo de dioctadecildimetil amônio (DODAB), pentanol e água, em uma região diluída. Esta é a primeira descrição de uma fase L3 preparada com um lipídio com uma cabeça polar relativamente pequena e duas cadeias de hidrocarboneto com 18 carbonos cada. A região no diagrama triangular pentanol/água/DODAB na qual a fase existe foi caracterizada utilizando as técnicas de isotropia óptica e anisotropia em relação a uma sonda de espectroscopia de ressonância paramagnética do elétron. A proposta de uma fase L3 foi feita por comparação com um sistema similar relatado pelo grupo de Monpellier. A descrição aceita é que, em uma relação estreita de concentração surfactante e cosurfactante, ocorre fusão de membrana com a formação de uma rede de bicamadas altamente interligadas e distribuídas aleatoriamente no espaço. A hipótese de formação da fase L3 é que o grupo hidroxila do pentanol se pareie com as cabeças de lipídios e esse fato é capaz de alterar a curvatura das bicamadas. As várias preparações de DODAB e pentanol mantiveram-se inalteradas durante pelo menos cinco anos apenas até 3 mM, a concentração máxima que pode ser chamada de L3, que é termodinamicamente estável. Para tornar o sistema mais atraente para muitos usos potenciais, é necessário aumentar a concentração do lipídio. Concentrações até 10 mM decompõem-se após algumas horas em pequenas gotas e cristais, a chamada multifase. O passo seguinte foi remover completamente o álcool por diálise contínua. O resultado foi o aparecimento de uma fase semelhante à água, que não pode ser obtida de outro modo. Uma sequência de medidas espectroscópicas e cromatográficas demonstrou que o álcool foi eliminado totalmente por diálise e o lipídio permanece retido. Há uma notável diferença com outros sistemas binários água/DODAB. Na mesma concentração, todos têm acentuada turbidez. A hipótese é que a presença de álcool na bicamada promove uma reorganização capaz de transformar um sistema particulado em bicontínuo. Está agora bem aceito que a força motriz dessas transformações são as mudanças de curvatura na bicamada. Os esforços para caracterizar esses sistemas são justificados, uma vez que são fáceis de preparar e têm utilizações potenciais como a síntese de compostos com poros mesoestruturados, transporte de drogas e cristalização de proteínas
Abstract: The amphiphilic L3 (sponge) phase was observed in the late 80's and represents a new class of self-assembly for surfactant-water systems. This work describes the discovery and subsequent characterization of a ternary phase composed of synthetic cationic lipid dioctadecildimetil ammonium bromide (DODAB), pentanol and water in a diluted region. This is the first description of a L3 phase prepared from a lipid with a relatively small polar head and two hydrocarbon chains with 18 carbons each one. The region of the triangle diagram in which there is L3 phase was characterized using optical isotropy and anisotropy to a probe with electron paramagnetic resonance spectroscopy technique. The proposal of an L3 phase was made by comparison with a similar system reported by the group of Montpellier. The description accepted is that in a narrow close ratio of surfactant/cosolvent concentrations, membrane fusion occurs with the formation of a highly interconnected and randomly distributed network of bilayers in space. The assumption of formation of the L3 phase is that the hydroxyl group of pentanol pairs with the lipid heads and this fact is able to change the bilayer curvature. The various DODAB/pentanol preparations remained unchanged and stable for five years only up to the concentration of 3 mM of lipid, the maximum concentration that can be called L3 phase, which is thermodynamically stable. To make the system more attractive for many potential uses it was necessary to increase the weight of the lipid. Concentrations up to 10 millimolar, after a few hours, break down into tiny droplets and small crystals, so-called multiphase. The next step was to completely remove the alcohol by continuous dialysis. The result was the appearance of a phase similar to water, which cannot be obtained otherwise. A sequence of spectroscopic and chromatography measurements showed that the alcohol was entirely eliminated by dialysis as the lipid was retained. There is a notable change when compared with other DODAB/water binary preparations. In the same concentration, all of them have pronounced turbidity. The hypothesis is that the presence of alcohol in the bilayer promotes reorganization, transforming a particulate into a bicontinuum system. Efforts to characterize these systems are justified because they are easy to prepare and have potential uses in the synthesis of inorganic solid new materials with nanostructured pores, and as drug carriers and vehicles for the crystallization of proteins
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutora em Engenharia Quimica
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Vatcha, Sorab R. "Gas separation by membranes : technology and business assessment". Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15233.
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Kosuri, Madhava Rao. "Polymeric membranes for super critical carbon dioxide (scCO2) separations". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28242.
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Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: William J. Koros; Committee Member: Amyn Teja; Committee Member: Carson Meredith; Committee Member: Sankar Nair; Committee Member: Wallace W. Carr.
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Nel, A. M. "Removal of organic foulants from capillary ultrafiltration membranes by use of ultrasound". Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1997.
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Govender, Selvakumaran. "Bioaffinity separation using ligand-modified pluronic and synthetic membranes". Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/16516.
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Thesis (PhD)--University of Stellenbosch, 2005.ENGLISH ABSTRACT: A new membrane based affinity separation system that is bio-specific, biocompatible, well characterised and capable of being regenerated or re-used is described. The amphiphilic non-ionic surfactant Pluronic® F108, was covalently derivatised to form two novel bioligands (Pluronic-Biotin and Pluronic-DMDDO) for the bio-specific immobilisation of avidin conjugated proteins and histidine tagged proteins respectively. Pluronic was also used to non-covalently functionalise nonporous membranes for ligand attachment and to simultaneously shield the surfaces from non-specific protein adsorption. Each component of this bioaffinity system (from the membrane matrix to the elution/desorption of the ligate/ligand system) was studied with the aim of producing a well characterised system and key quantitative data for the development of a robust, reliable, re-usable and scalable technology. Specifically, this study describes: 1. The fabrication and partial characterisation of nonporous planar and capillary membranes as model affinity matrices. 2. The development and evaluation of a robust protocol for solvent desorption and accurate colorimetric quantification of Pluronic® F108 and its derivatives. 3. Interfacial analysis of Pluronic adsorption onto nonporous affinity membranes, including the direct solid-state analysis of model, halogenated Pluronic derivatives using nuclear microprobe analysis. 4. Development of a surfactant based protocol for affinity membrane regeneration and re-use. 5. Specific bioaffinity immobilisation of avidin conjugated peroxidase onto biotinylated membranes in the presence of model protein foulants. 6. Cloning and expression of C-terminal hex-histidine tagged human cytochrome b5 into the bacterial expression system E. coli BL-21 DE3. 7. Development and characterisation of an immobilised metal affinity membrane system for metal chelation (Ni2+, Cu2+ and Zn2+) using a new chelator Pluronic- N,N-dicarboxymethyl-3,6-diazaoctanedioate and the bio-specific immobilisation of N-terminal hex-histidine tagged pantothenate kinase.
AFRIKAANSE OPSOMMING: 'n Nuwe membraan-gebaseerde affiniteitskeidingsisteem word beskryf wat biospesifiek, bioversoenbaar en goed gekarakteriseer is, en geregenereer of hergebruik kan word. Die amfifiliese nie-ioniese surfaktant Pluronic is kovalent gederivatiseer om twee nuwe bioligande (Pluronic-Biotien en Pluronic-DMDDO) te vorm vir biospesifieke immobilisering van proteïnligate. Pluronic is ook gebruik om nie-poreuse membrane niekovalent te funksionaliseer vir ligandaanhegting en om hulle oppervlaktes teen niespesifieke proteïen-adsorbsie af te skerm. Elke komponent van hierdie bioaffiniteitsisteem (van die membraanmatriks tot die uitwas/desorpsie van die ligaat/ligand sisteem) is ondersoek met die doel om 'n goed-gekarakteriseerde sisteem te produseer en om kwantitatiewe data te genereer vir die ontwikkeling van 'n robuuste, betroubare, herbruikbare en opskaleerbare tegnologie. Hierdie studie beskryf spesifiek: 1. Die fabrisering en gedeeltelike karakterisering van nie-poreuse planêre en kapillêre membrane as model affiniteitsmatrikse. 2. Die ontwikkeling en evaluering van 'n robuuste protokol vir oplosmiddel desorpsie en akkurate kolorimetriese kwantifikasie van Pluronic® F108 en afgeleides daarvan. 3. Intervlakanalises van Pluronic adsorpsie op nie-poreuse affiniteitsmembrane, insluitend die direkte vastetoestand analise van model ligand-gemodifiseerde Pluronic deur die gebruik van kern-mikrosonde analise. 4. Ontwikkeling van 'n surfaktant-gebaseerde protokol vir affiniteitsmembraan regenerering en hergebruik. 5. Spesifieke bioaffiniteitsimmobilisering van avidien-gekonjugeerde peroksidase op gebiotinileerde membrane in die teenwoordigheid van model bevuilende proteïne. 6. Klonering en uitdrukking van C-terminaal hex-histidien geëtiketeerde menslike sitochroom b5 in die bakteriële uitdrukkingsisteem E. coli BL-21 DE3. 7. Ontwikkeling en karakterisering van 'n geïmmobiliseerde metaalaffiniteitsmembraansisteem vir metaalchelering (Ni2+, Cu2+ en Zn2+) met behulp van die nuwe cheleerder Pluronic-N,N-dikarboksimetiel-3,6- diasaoktaandioaat en die bio-spesifieke immobilisering van N-terminaal hexhistidiengeëtiketerde pantotenaatkinase.
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Kiyono, Mayumi. "Carbon molecular sieve membranes for natural gas separations". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42798.
Testo completoAbstract (sommario):
A new innovative polymer pyrolysis method was proposed for creation of attractive carbon molecular sieve (CMS) membranes. Oxygen exposure at ppm levels during pyrolysis was hypothesized and demonstrated to make slit-like CMS structures more selective and less permeable, which I contrary to ones expectation. Indeed prior to this work, any exposure to oxygen was expected to result in removal of carbon mass and increase in permeability. The results of this study indicated that the separation performance and CMS structure may be optimized for various gas separations by careful tuning of the oxygen level. This finding represents a breakthrough in the field of CMS membranes. Simple replacement of pyrolysis atmospheres from vacuum to inert can enable scale-up. The deviation in CMS membrane performance was significantly reduced once oxygen levels were carefully monitored and controlled. The method was shown to be effective and repeatable not only with dense films but also with asymmetric hollow fiber membranes. As a result, this work led the development of the "inert" pyrolysis method which has overcome the challenges faced with previously studied pyrolysis method to prepare attractive CMS membranes.
The effect of oxygen exposure during inert pyrolysis was evaluated by a series of well-controlled experiments using homogeneous CMS dense films. Results indicated that the oxygen "doping" process on selective pores is likely governed by equilibrium limited reaction rather than (i) an external or (ii) internal transport or (iii) kinetically limited reaction. This significant finding was validated with two polyimide precursors: synthesized 6FDA/BPDA-DAM and commercial Matrimid®, which implies a possibility of the "inert" pyrolysis method application extending towards various precursors. The investigation was further extended to prepare CMS fibers. Despite the challenge of two different morphologies between homogeneous films and asymmetric hollow fibers, the "inert" pyrolysis method was successfully adapted and shown that separation performance can be tuned by changing oxygen level in inert pyrolysis atmosphere. Moreover, resulting CMS fibers were shown to be industrially viable. Under the operating condition of ~80 atm high pressure 50/50 CO2/CH4 mixed gas feed, the high separation performance of CMS fibers was shown to be maintained. In addition, elevated permeate pressures of ~20 atm did effect the theoretically predicted separation factor. While high humidity exposures (80%RH) resulted in reduced permeance, high selectivity was sustained in the fibers. Recommendations to overcome such negative effects as well as future investigations to help CMS membranes to be commercialized are provided.
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Song, Qilei. "Polymer molecular sieve membranes". Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/280264.
Testo completoAbstract (sommario):
Sustainable energy supply and environmental protection are the major global scientific challenges in the 21st century, such as greenhouse gas capture, natural gas production, desalination of seawater for clean water production. Membrane separation technology offers attractive energy-efficient and environmental-friendly solutions to these challenges. This PhD thesis is focused on design and fabrication of membranes from novel molecularly defined polymers and understanding their physical properties, particularly the transport properties of gas molecules in polymer membranes. First, we demonstrate a simple approach of fabricating novel polymer nanocomposite membranes using established colloidal science. Crystalline microporous zeolitic imidazolate frameworks (ZIFs) nanocrystals are incorporated into a polyimide polymer matrix via solution mixing. The resulting nanocomposite membranes show excellent dispersion of nanoparticles, good adhesion at the interface, and enhanced gas permeability while the selectivity remain at high level. We then fabricated membranes from novel microporous polymers, polymers of intrinsic microporosity (PIMs). Using the PIM-1 polymer as a prototype, we discovered that ultraviolet irradiation of PIM-1 membranes in the presence of oxygen induces oxidative chain scission at the surface, resulting in local densification and structural transformation of free volume elements. Consequently, the membrane become asymmetric with a more gas-selective layer formed at the surface, while the overall permeability maintains at high level. Finally, we report a simple thermal oxidative crosslinking method to tailor the architecture of channels and free volume elements in PIM-1 polymer membrane by heat treatment in the presence of trace amounts of oxygen molecules. The resulting covalently crosslinked polymer networks offer superior thermal stability, chemical stability, reasonable mechanical strength, and enhanced rigidity. Most important of all, thermally crosslinked PIM-1 polymer membranes show significantly enhanced molecular sieving functions that yield remarkably high selectivity and high gas permeability, which surpass the upper bound that has been limiting the polymer membranes for decades. We also demonstrate that the thermal crosslinking method is effective for crosslinking of nanocomposite membranes with porous or nonporous fillers. These microporous molecular sieve membranes are promising for a wide range of molecular-level separation applications.
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Hancocks, Robin Danyel. "Controlled emulsification using microporous membranes". Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3057/.
Testo completoAbstract (sommario):
Emulsions are a vital part of many products in everyday use, such as foods, cosmetics, and even construction materials. Membrane emulsification is a technique which has been used to produce emulsions in a manner contrary to the traditional methods where droplets are broken and re-broken to make smaller and smaller droplets, and instead each droplet is individually formed at a pore on the surface of the membrane. This research compared two of the most favoured membrane emulsification techniques; cross-flow and rotating membrane emulsification. Two systems were built for producing emulsions using tubular microporous membranes, made from shirasu porous glass, polymer, ceramic and stainless steel. One device employed a cross-flow system providing shear to detach the nascent droplets from the membrane pores whilst the other system employed a rotated membrane to produce both shear and potentially centripetal force at the membrane surface. Both systems were used to create emulsions, and the effects of various settings of the systems were investigated. A direct comparison between cross flow membrane emulsification and rotating membrane emulsification were achieved for the first time, as the same membranes were available for both systems. The modular interchangeable nature of the membranes in the systems also allowed direct comparison between the various different membrane types tested. The distinct differences in the structure and materials of the membranes tested was compared, and its effects elucidated, as the different membrane types each showed different advantages and disadvantages when producing droplets. It was shown that the membrane pore size is a major factor on the size of the droplets produced, and the membrane pore size distribution span affects the size distribution span of the droplets. Increasing the emulsifier concentration decreases droplet size, as does increasing the shear force applied to the forming droplets, either by increasing the cross-flow velocity or the rotation rate. Increasing the pressure applied to force the dispersed phase through the membrane increases flux rate, but also increases droplet size slightly. The relative viscosity of the two phases being emulsified has an effect on the droplet size; increasing the continuous phase viscosity decreases droplet size, and increasing dispersed phase viscosity increases droplet size. The systems performed equally well making water in oil, as oil in water emulsions. Although the rotating membrane system produces lower shear rates than the cross-flow system, similar droplet diameters were produced, implying that detachment is enhanced by the rotation, showing a clear advantage to rotating membrane emulsification. The systems were also used to produce various more complex particles, including double emulsions and gelled beads, and the level of control over the phases afforded by membrane emulsification was shown to be an advantage in the production of such microstructures.
19
Ma, Canghai. "Optimization of asymmetric hollow fiber membranes for natural gas separation". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43700.
Testo completoAbstract (sommario):
Compared to the conventional amine adsorption process to separate CO₂ from natural gas, the membrane separation technology has exhibited advantages in easy operation and lower capital cost. However, the high CO₂ partial pressure in natural gas can plasticize the membranes, which can lead to the loss of CH₄ and low CO₂/CH₄ separation efficiency. Crosslinking of polymer membranes have been proven effective to increase the CO₂ induced plasticization resistance by controlling the degree of swelling and segmental chain mobility in the polymer. This thesis focuses on extending the success of crosslinking to more productive asymmetric hollow fibers. In this work, the productivity of asymmetric hollow fibers was optimized by reducing the effective selective skin layer thickness. Thermal crosslinking and catalyst assisted crosslinking were performed on the defect-free thin skin hollow fibers to stabilize the fibers against plasticization. The natural gas separation performance of hollow fibers was evaluated by feeding CO₂/CH₄ gas mixture with high CO₂ content and pressure.
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Meyer, Faiek. "Hydrogen selective properties of cesium-hydrogensulphate membranes". Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_5047_1233727545.
Testo completoAbstract (sommario):
Over the past 40 years, research pertaining to membrane technology has lead to the development of a wide range of applications including beverage production, water purification and the separation of dairy products. For the separation of gases, membrane technology is not as widely applied since the production of suitable gas separation membranes is far more challenging than the production of membranes for eg. water purification. Hydrogen is currently produced by recovery technologies incorporated in various chemical processes. Hydrogen is mainly sourced from fossil fuels via steam reformation and coal gasification. Special attention will be given to Underground Coal Gasification since it may be of great importance for the future of South Africa. The main aim of this study was to develop low temperature CsHSO4/SiO2 composite membranes that show significant Idea selectivity towards H2:CO2 and H2:CH4.
21
Liu, Junqiang. "Development of next generation mixed matrix hollow fiber membranes for butane isomer separation". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42807.
Testo completoAbstract (sommario):
Mixed matrix hollow fiber membranes maintain the ease of processing polymers while enhancing the separation performance of the pure polymer due to inclusion of molecular sieve filler particles. This work shows the development process of high loading mixed matrix hollow fiber membranes for butane isomer separation, from material selection and engineering of polymer-sieve interfacial adhesion to mixed matrix hollow fiber spinning.
The matching of gas transport properties in polymer and zeolite is critical for forming successful mixed matrix membranes. The nC4 permeability in glassy commercial polymers such as Ultem® and Matrimid® is too low (< 0.1 Barrer) for commercial application. A group of fluorinated (6FDA) polyimides, with high nC4 permeability and nC4/iC4 selectivity, are selected as the polymer matrix. No glassy polymers can possibly match the high permeable MFI to make mixed matrix membranes with selectivity enhancement for C4s separation. Zeolite 5A, which has a nC4 permeability (~3 Barrer) and nC4/iC4 selectivity (essentially ∞), matches well with the 6FDA polymers. A 24% nC4/iC4 selectivity enhancement was achieved in mixed matrix membranes containing 6FDA-DAM and 25 wt% treated 5A particles. A more promising mixed matrix membrane contains 6FDA-DAM-DABA matrix and 5A, because of a better match of gas transport properties in polymer and zeolite.
Dual layer hollow fibers, with cellulose acetate core layer and sheath layers of 6FDA polyimides, were successfully fabricated. Successive engineering of the 6FDA sheath layer and the dense skin is needed for the challenging C4s separation, which is extremely sensitive to the integrity of the dense skin layer. The delamination-free, macrovoid-free dual layer hollow fiber membranes provide the solution for the expensive 6FDA polyimides spinning. Mixed matrix hollow fiber membranes are spun base on the platform of 6FDA/Cellulose acetate dual layer hollow fibers. Preliminary results suggest that high loading mixed matrix hollow fiber membranes for C4s is feasible. Following research is needed on the fiber spinning with well treated zeolite 5A nanoparticles.
The key aspect of this research is elucidating the three-step (sol-gel-precipitation) mechanism of sol-gel-Grignard treatment, based on which further controlling of Mg(OH)2 whisker morphologies is possible. A Mg(OH)2 nucleation process promoted by acid species is proposed to explain the heterogeneous Mg(OH)2 growing process. Different acid species were tried: 1) HCl solution, 2) AlClx species generated by dealumination process and 3) AlCl3 supported on zeolite surfaces. Acids introduced through HCl solution and dealumination are effective on commercial 5A particles to generate Mg(OH)2 whiskers in the sol-gel-Grignard treatment. Supported AlCl3 is effective on both commercial and synthesized 5A particles (150 nm-1 µm) during the sol-gel-Grignard treatment, in terms of promoting heterogeneous Mg(OH)2 whiskers formation. But the byproduct of Al(OH)3 layer separates the Mg(OH)2 whiskers from zeolite surface, and leads to undesirable morphologies for polymer-zeolite interfacial adhesion. The elucidation of sol-gel-Grignard mechanism and importance of zeolite surface acidity on Mg(OH)2 formation, builds a solid foundation for future development towards ''universal'' method of growing Mg(OH)2 whiskers on zeolite surfaces.
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Costello, Michael John School of Chemical Engineering & Industrial Chemistry UNSW. "SHELL-SIDE FLUID DYNAMICS AND MASS TRANSFER THROUGH HOLLOW FIBRE MEMBRANE MODULES". Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 1995. http://handle.unsw.edu.au/1959.4/17042.
Testo completoAbstract (sommario):
There is a considerable volume of work available in literature which suggests that the performance of axial-flow hollow fibre membrane modules is limited by poorly distributed flow through the shell-side. This study was commissioned to examine the distribution of shell-side flow and its effect on mass transfer and to compare the performance measured by the axial-flow configuration to that obtained by a commonly used alternative known as the helically-wound module design. Laminar flow and mass transfer models have been developed to examine performance through axial-flow hollow fibre modules. These models also consider deviations from laminar flow in the form of turbulence and hydrodynamically undeveloped flow. Modelling analysis on four fibre bundle cross-sections quantify the extent to which channelling limits flow and mass transfer performance. Experimental flow and mass transfer work with locally fabricated hollow fibre modules demonstrated some inconsistencies with axial laminar flow modelling. Pressure drop and mass transfer results exceeded predictions from modelling. This thesis has hypothesised that fibres in axial-flow hollow fibre modules are not aligned as straight and parallel rods (as assumed in modelling) but interweave. Fibre interweaving results in flows between ducts. Such flows create mixing between ducts which results in more intimate contact between the flow and membrane surface, the consequence being higher pressure drop and higher mass transfer. The implication from this work was that axial flow and mass transfer modelling was limited in its use for characterisation of shell-side performance. The experience with helically-wound hollow fibre membrane modules (also fabricated locally) was that, by deliberately inducing flow between ducts, it was possible to considerably improve mass transfer performance. It was found that, whilst helically-wound modules could not be packed as tightly as axial-flow modules and required more sophisticated fabrication techniques, the benefit in their use arose from a substantial improvement in the level of shell-side mass transfer.
23
Bae, Tae-Hyun. "Engineering nanoporous materials for application in gas separation membranes". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42712.
Testo completoAbstract (sommario):
The main theme of this dissertation is to engineer nanoporous materials and nanostructured surfaces for applications in gas separation membranes. Tunable methods have been developed to create inorganic hydroxide nanostructures on zeolite surfaces, and used to control the inorganic/polymer interfacial morphology in zeolite/polymer composite membranes. The study of the structure-property relationships in this material system showed that appropriate tuning of the surface modification methods leads to quite promising structural and permeation properties of the membranes made with the modified zeolites. First, a facile solvothermal deposition process was developed to prepare roughened inorganic nanostructures on zeolite pure silica MFI crystal surfaces. The functionalized zeolite crystals resulted in high-quality ̒mixed matrix̕ membranes, wherein the zeolite crystals were well-adhered to the polymeric matrix. Substantially enhanced gas separation characteristics were observed in mixed matrix membranes containing solvothermally modified MFI crystals. Gas permeation measurements on membranes containing nonporous uncalcined MFI revealed that the performance enhancements were due to significantly enhanced MFI-polymer adhesion and distribution of the MFI crystals. Solvothermal deposition of inorganic nanostructures was successfully applied to aluminosilicate LTA surfaces. Solvothermal treatment of LTA was tuned to deposit smaller/finer Mg(OH)₂ nanostructures, resulting in a more highly roughened zeolite surface. Characterization of particles and mixed matrix membranes revealed that the solvothermally surface-treated LTA particles were promising for application in mixed matrix membranes. Zeolite LTA materials with highly roughened surfaces were also successfully prepared by a new method: the ion-exchange-induced growth of Mg(OH)₂ nanostructures using the zeolite as the source of the Mg²⁺ ions. The size/shape of the inorganic nanostructures was tuned by adjusting several parameters such as the pH of the reagent solution and the amount of magnesium in the substrates and systematic modification of reaction conditions allowed generation of a good candidate for application in mixed matrix membranes. Zeolite/polymer adhesion properties in mixed matrix membranes were improved after the surface treatment compared to the untreated bare LTA. Surface modified zeolite 5A/6FDA-DAM mixed matrix membranes showed significant enhancement in CO₂ permeability with slight increases in CO₂/CH₄ selectivity as compared to the pure polymer membrane. The CO₂/CH₄ selectivity of the membrane containing surface treated zeolite 5A was much higher than that of membrane with untreated zeolite 5A. In addition, the use of metal organic framework (MOF) materials has been explored in mixed matrix membrane applications. ZIF-90 crystals with submicron and 2-μm sizes were successfully synthesized by a nonsolvent induced crystallization technique. Structural investigation revealed that the ZIF-90 particles synthesized by this method had high crystallinity, microporosity and thermal stability. The ZIF-90 particles showed good adhesion with polymers in mixed matrix membranes without any compatibilization. A significant increase in CO₂ permeability was observed without sacrificing CO₂/CH₄ selectivity when Ultem® and Matrimd® were used as the polymer matrix. In contrast, mixed matrix membranes with the highly permeable polymer 6FDA-DAM showed substantial enhancement in both permeability and selectivity, as the transport properties of the two phases were more closely matched.
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Rao, Prithi Ananthayya Buschle-Diller Gisela. "Permeation of vapors through porous membranes". Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Spring/master's/RAO_PRITHI_41.pdf.
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Lanigan, William Robert. "A study of photopolymerized microporous membranes". Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/8583.
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26
Ogbuke, Ikechukwu. "Preparation, characterization and testing of inorganic ceramic membranes". Thesis, Robert Gordon University, 2013. http://hdl.handle.net/10059/2111.
Testo completoAbstract (sommario):
A novel approach to enhance the concentration of Carbon dioxide to economic scale using low efficient Inorganic Ceramic membranes has been proposed. This was achieved by the addition of second and third stage permeation trains to the existing low CO2 recovering Ceramic Inorganic membranes. The Inorganic Ceramic membrane development involved modification of Alpha Alumina support with Gamma Alumina for improved surface area. Further modifications with Magnesium Oxide and Silicon Elastomer showed increase in the selectivity of Carbon dioxide molecules over Nitrogen, Methane, Argon, and Helium molecules, both in pure and mixture forms. A simulated flue gas feed concentration of CO2-14% and N2-86% was found to be concentrated more than 90% of CO2. The Carbon dioxide permeability was found to decrease as the membrane thickness and number of dipping increased, whereas, the selectivity of the Carbon dioxide over Nitrogen, Argon, Helium and Methane molecules improved with the use of modified membranes compared to membrane support only. The testing of the fabricated membrane demonstrated that modified membrane at third stage permeation at a pressure drop of 9.00KPa and operating temperature of 296K was capable of recovering more than 90% of Carbon dioxide from a feed gas mixture of 14%-CO2 and N2-86%.The permeability of the Carbon dioxide gas molecules that was recovered at the above listed operating conditions was 4.26X10-12 (mol.m/m2.s.Pa). This was achieved by surface flow mechanism and membrane pore sizes estimated were found to be macroporoes and mesopores with their EDXA and SEM images. A numerical algorithm was used to estimate the errors. The error was found to decrease as the permeation value increases.
27
Das, Mita. "Membranes for olefin/paraffin separations". Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37110.
Testo completoAbstract (sommario):
The goal of this project was to develop a mixed matrix membrane with enhanced properties for propylene/propane separations. To start with the project, one of the high performance 6FDA based polyimides was identified as the polymer matrix for the rest of the project. The chosen polymer (6FDA-6FpDA) was successfully synthesized in the laboratory.
During the synthesis process the key objectives for high molecular weight and low polydispersity index polymer were identified. High molecular weight 6FDA-6FpDA was achieved via laboratory synthesis and was tested successfully.
After successful synthesis of the high performance polymer, pure polymer dense films were tested for transport properties. One problem identified with 6FDA-6FpDA polymer films for propylene/propane separations was plasticization. A major objective of this research was to develop a method for plasticization suppression. A carefully controlled annealing procedure with high temperature permeation experiments was used in this research to suppress plasticization in a mixed gas environment. To the best of our knowledge, this is for the first time plasticization suppression was achieved with pure polymeric membrane material for propylene/propane separations with pure and mixed gases. The observed mixed gas experimental selectivity was lower than the pure gas selectivity which was explained by the combination effect of dual mode and bulk flow effect.
The last objective of this project was to successfully incorporate molecular sieve materials to form a mixed matrix membrane hybrid material with enhanced transport properties First, an ideal molecular sieve for propylene/propane separation was identified and characterized. AlPO-14 was chosen for this research following its success with propylene/propane pressure swing adsorption. Mixed matrix membranes were successfully produced and tested for enhanced transport properties. Both pure and mixed gas results showed promising results with enhanced propylene permeability and propylene/propane selectivity. The experimental results were modeled with the Cussler and Maxwell models. A modified Cussler model was presented in this work. This is the first time an enhancement in the transport properties with mixed matrix membrane for propylene/propane separations has been observed. This fundamental dense film work holds a bright future for the scale up of propylene/propane separations.
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Williams, Steffan Richard. "Recovery of small organics from natural sources using membrane technology". Thesis, Swansea University, 2015. https://cronfa.swan.ac.uk/Record/cronfa43185.
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Lydon, Megan Elizabeth. "Properties of inorganically surface-modified zeolites and zeolite/ polyimide nanocomposite membranes". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49069.
Testo completoAbstract (sommario):
Mixed matrix membranes (MMMs) consisting of a polymer bulk phase and an inorganic dispersed phase have the potential to provide a more selective membrane because they incorporate the selectivity of a zeolite dispersed phase while maintaining the ease of use of a polymer membrane. A critical problem in MMM applications is control over the polymer-zeolite interface adhesion during fabrication which can detrimentally impact membrane performance. In this work, MgOxHy (1≤x≤2, 0≤y≤2) nanostructures have been grown on pure-silica MFI and aluminosilicate LTA zeolites through four surface deposition techniques: Grignard decomposition reactions, solvothermal and modified solvothermal depositions, and ion-exchange induced surface crystallization. The structural properties of the surface nanostructures produced by each of the four methods were thoroughly characterized for their morphology, crystallinity, porosity, surface area, elemental composition, and these properties were used to predict the method’s suitability for use in composite membranes. The nanostructured zeolites were used in mixed matrix membranes (MMMs) at two MMMs weight loadings. The dispersion, mechanical properties, and CO₂/CH₄ gas separation properties were measured MMMs made with each method of functionalized LTA. All functionalization methods improve adhesion with the polymer observable by microscopy, the dispersion of particles, and the elastic modulus and hardness of the membrane. Gas permeation measurements prove the quality and effectiveness of the Ion Exchange membrane for CO₂/CH₄ separation by its significant increase in selectivity over the pure polymer. Lastly, the interface between the two materials was studied by probing the interfacial polymer mobility using NMR spin-spin relaxation measurements and mechanical mapping of membrane cross sections. It was shown that the nanostructures have both steric and chemical interactions with the polymer. Mapping of the elastic modulus indicated that functionalization methods that resulted in poorer zeolite coverage also disrupted the mechanical properties of the membrane at the interface of the materials. The investigations in this thesis provide detailed structure-property relationships of surface-modified molecular sieves and nanocomposite membranes fabricated using these materials, allowing a rational approach to the design of such materials and membranes.
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Wicaksana, Filicia School of Chemical Engineering & Industrial Chemistry UNSW. "Submerged hollow fibre membranes in bubbling systems". Awarded by:University of New South Wales. School of Chemical Engineering and Industrial Chemistry, 2006. http://handle.unsw.edu.au/1959.4/25998.
Testo completoAbstract (sommario):
This study focuses on the optimisation of submerged hollow fibre membrane performance by analysing the role of air sparging on the reduction of membrane fouling. In submerged hollow fibre membranes, rising bubbles have been shown to induce shear, liquid movement and fibre displacement. The interaction between fibre movement induced by bubbling and the microfiltration performance was assessed for various parameters (fibre tightness, fibre length, fibre diameter, air flowrate, nozzle size, and feed concentration). A model feed of yeast suspension and a series of isolated fibres were used. The fibre movement was assessed by monitoring the displacement using video recording. Bubble population parameters were also measured. The results suggest that bubbleinduced fibre movement plays an important role in controlling membrane fouling. Investigations of the critical flux at various operating conditions also supported these conclusions. Since energy consumption for aeration is a major contributor to the cost in submerged membranes, the potential to minimise the aeration cost has been tested by implementing intermittent aeration and different nozzle sizes. It was found that an optimum condition associated with a low fouling rate could be reached by combining various aeration intermittencies and nozzle sizes. An attempt to suppress fouling without aeration was made by incorporating vibrations into a submerged hollow fibre membrane system. The effects of vibration frequency, type of yeast (washed and unwashed) on the filtration performance were observed. The impact of coagulant addition on filtration enhancement was also analysed. The performance of microfiltration was evaluated based on its critical flux value. The findings in this preliminary study indicated potential fouling control by applying vibrations to submerged membranes. A semi-empirical model was developed to predict the filtration behaviour by taking into account the bubble-induced shear and fibre movement. The predicted critical flux values suggested that membrane fouling appears to be more prominent at low air flowrate, with tight fibres, and higher feed concentrations. The model fits the experimental data with discrepancies from approximately 0.3% to 20%. The predicted filtration profiles at different operating modes demonstrate the importance of bubble-induced shear and fibre movement in the improvement of filtration performance.
31
Diamond, Geoffrey Graham. "Organically templated inorganic membranes for gas separation". Thesis, University of Warwick, 2001. http://wrap.warwick.ac.uk/3071/.
Testo completoAbstract (sommario):
This work is an attempt to develop inorganic gas separation membranes for the purposes of separating high temperature binary gaseous mixtures. Carbon dioxide and nitrogen mixtures are the focus of this work but other mixtures could be used. The membrane synthesis route is derived from the sol-gel technique. It relies upon micropores being produced within the membrane and this is accomplished by the thermal removal of organic ligands (the "templates"). The thermal stability and structural evolution with temperature of these materials has been characterised with TGA, DTA, FTIR, 13C CP MAS NMR 11B MAS NMR and 29Si MAS NMR investigations. The research was demarcated into the comparisons between two systems: non-borosilicate and borosilicate. The borosilicate systems were thought to merit special investigation due to the known property of the boron atom in borosiloxane bonds to act as a network enhancer. Three different organic ligands; methyl, ethyl and phenyl have been investigated. The higher thermal stability (~770K) and the known CO2 affinity of the phenyl ligand, led to the production of materials containing both the methyl ligand (to generate porosity) and the phenyl ligand (to hopefully provide CO2 affinity). Other structures with methyl as a backbone but containing boron were found to have superior performance in terms of separation factors, robustness and durability. The permeability of CO2, N2 Ar and He was measured through all the membranes systems, as a function of pressure, temperature and time. In both the borosilicate and non-borosilicate systems, CO2 was found to permeate preferentially over He in the best specimens. This was despite its much larger molecular diameter and for both classes of system, permeance was observed to decrease with elevated temperatures. The general conclusion that for both classes of system the mechanism of preferential CO2 transport is activated surface diffusion. Evidence of gradual adsorption of CO2 by the non-borosilicate systems was indicated by their steady decrease in performance with time when exposed to this species. (Such degradation in permeance performance was not observed for those non-borosilicate systems that had not been exposed to CO2 but just N2, He or Ar. The borosilicate systems however, were far more robust. Any decrease in permeance with time, after exposure to CO2 under pressure, was orders of magnitude slower than with the non-borosilicate systems. For the non-borosilicate systems the decrease in permeability is deemed to be due to CO2 chemisorption and must be related to the surface diffusion. For the non-borosilicate systems however, chemisorption appears to play a far less important role. Structural studies (NMR and FTIR) of all the systems indicated that the pyrolysis of the organic templates produces both siloxane and in the case of the borosilicate systems, borosiloxane linkages as well. These are assumed to be the generators of the sites through which surface diffusion occurs. For the non-borosilicate systems, surface diffusion seems to be improved by the incorporation of phenyl ligands within the siloxane network. However, this is associated with accelerated adsorption and decrease in overall performance. For the borosilicate systems, the most successful system had a methyl backbone and decreased in performance very gradually and after that remained constant except for long-term modulations which were mirrored by the inert species as well. Thermally rejuvenating the degraded non-borosilicate membranes did not meet with success. However, the borosilicate systems did partially respond to this treatment and regained a significant fraction of their original performance. The conclusion is that in the non-borosilicate system chemisorption dominates over physisorption as a CO2 selectivity mechanism, whilst for the borosilicate systems the reverse appears to be true.
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Schneider, Markus. "Applications of hydrophobic porous membranes in mammalian cell culture technology /". [S.l.] : [s.n.], 1995. http://library.epfl.ch/theses/?nr=1412.
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Harmzen, Elrika. "Study of nanofibrous membranes for application in post harvest technology". Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86771.
Testo completoAbstract (sommario):
Thesis (MSc)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Grapes are lost annually due to spoilage by Botrytis cinerea. Botrytis cinerea is currently controlled using fungicides and SO2 fumigation in storage rooms but with limited success. Although these techniques have been used for decades they have been associated with numerous of disadvantages. Fungicides are restricted from being used during storage due to legislation and toxicity of the fungicides present on the surface of the berries. SO2 fumigation does not kill the dormant infections present inside the grape tissue and if the SO2 concentration is too high the berries are damaged. During this study two different polymer nanofibrous platforms was synthesized in an attempt to prevent the rotting effect of B. cinerea. The first polymer was modified to yield a polymer with a positively charged quaternized nitrogen moiety, which was subsequently reacted with sodium metabisulfite through an ion exchange process. The modified polymer was electrospun into nanofibrous mats for the benefit of the nanofibers’ high available surface area. A further functionalization was done to increase the quantity of sodium metabisulfite on the surface of the polymer nanofibers. Sodium metabisulfite salt released SO2 gas upon reaction with water vapour present in the atmosphere which resulted in the inhibition of conidial germination of B. cinerea. The second polymer was synthesized and then electrospun into polymer nanofibrous mats followed by chemical modification of the electrospun polymer nanofibers. This post-electrospun modification resulted in the covalent attachment of a fungicide-derivative to the surface of the polymer nanofibers. The fungicide-derivative showed excellent inhibition of B. cinerea mycelium growth. Anti-fungal studies were conducted using the two modified polymer nanofibrous mats against B. cinerea to evaluate these nanofibrous surfaces as B. cinerea inhibiting membranes. Results indicated that B. cinerea conidial germination and mycelium growth were successfully inhibited.
AFRIKAANSE OPSOMMING: Druiwe bederf jaarliks weens die verrottende effek van die fungi Botrytis cinerea. Botrytis cinerea word tans beheer deur gebruik te maak van swamdoders en swaweldioksied (SO2) besproeiings in stoorkamers, maar met beperkte sukses. Alhoewel hierdie tegnieke al vir dekades in gebruik is, word dit geassosieer met verskeie probleme. Die gebruik van swamdoders word in stoorkamers verbied, weens die moontlike skadelike inname daarvan deur die mens aangesien die swamdoders op die druiwe se oppervlakte teenwoordig is. SO2-gasbesproeiings maak nie dormante infeksies binne-in die druiwe self dood nie en indien SO2 -konsentrasies te hoog is kan dit die druiwe beskadig. Tydens hierdie studie is twee verskillende polimeer-nanoveselplatforms gesintetiseer met die doel om die verrottende effek van B. cinerea te voorkom. Die eerste polimeer is aangepas met ’n primêre amienverbinding met die doel dat dit deur ‘n opvolgende modifikasiereaksie verander om sodoende ’n polimeer met ‘n kwatenêre ammoniumgroep te verkry. Die doel van die kwatenêre eienskap is dat ioniese uitruiling plaasvind tussen die anioon van die polimeer en die natruimmetabisulfiet-anioon van die sout. Die voorbereide kopolimeer is geëlektrospin in nanoveselmatte deur middel van die enkelnaald-en-enkelbal-elektrospintegniek om SMI-qC12 nanovesels te lewer wat gefunksionaliseer is. Die nanoveselmatte is na die elektrospinproses verder aangepas om die hoeveelheid natruimmetabisulfiet op die oppervlak van die nanovesels te verhoog. Die natruimmetabisulfiet stel SO2-gas vry sodra dit in aanraking kom met waterdamp in die lug wat ’n beperkende effek op spoorontkieming van B. cinerea tot gevolg het. Die tweede polimeer is voor en na die elektrospinproses gefunksionaliseer met gesintetiseerde organiese verbindings (swamdoder). Die aanpassing van die polimeer met die organiese verbindings het plaasgevind op ‘n kovalente wyse om te verhoed dat die organiese verbinding vrygelaat word tydens gebruik. Die organiese verbindings het effektiewe beperking van miselium-groei getoon. Anti-swamstudies is uitgevoer tussen die twee gefunksionaliseerde polimeer platforms en B. cinerea om die oppervlaktes van die gefunksionaliseerde polimeer/nanovesels te evalueer as B. cinerea beperkende platforms. Resultate het aangetoon dat spoorontkieming en miselium groei van B. cinerea suksesvol beperk is.
34
Lin, Lin. "On the Generation and Detection of Ultrasonic Plate Waves in Microporous Polymeric Material". Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/LinL2003.pdf.
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Carruthers, Seth Blue. "Integral-skin formation in hollow fiber membranes for gas separations". Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3036162.
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Martula, David Stefan. "Coalescence-induced coalescence in polymeric membrane formation /". Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004333.
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Troup, Gregory Marshall Wrenn Steven Parker Dr. "Fluorescence investigation of laterally phase-separated cholesterol rich domains in model lipid membranes using the membrane probe 1-myristoyl-2-[12-[(5-dimethylamino-1-naphthalenesulfonyl)amino]dodecanoyl]-sn-Glycero-3-phosphocholine (A) /". Philadelphia, Pa. : Drexel University, 2004. http://dspace.library.drexel.edu/handle/1860/345.
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38
Sejour, Hensley. "Investigation of Dithiolenes for Propylene/Propane Membrane Separations". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19697.
Testo completoAbstract (sommario):
Polyimide membranes containing nickel dithiolenes were investigated for the separation of propylene and propane. Permeation and sorption experiments were conducted as well thermal property analyses. Results indicate that the dithiolene has an antiplasticizing effect on the polymers studied. Upon addition of the dithiolene there is a subsequent reduction in the permeability coefficient and the permeability selectivity remains relatively unchanged. There is some evidence of increases in solubility selectivity, but a larger decrease in diffusivity selectivity results in a decrease in the permeability selectivity. Investigation of the thermal and mechanical properties of dithiolene-containing films indicates a reduction in fractional free volume as well as the glass transition temperature when compared to the pure polymer. There is also an increase in the modulus of the films upon addition of the dithiolene. The implications of these results and their correlation with antiplasticization are discussed.
39
Svang-Ariyaskul, Apichit. "Chiral separation using hybrid of preferential crystallization moderated by a membrane barrier". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33909.
Testo completoAbstract (sommario):
The major innovation of this work is an establishment of a novel chiral separation process using preferential crystallization coupled with a membrane barrier. This hybrid process was proved to be promising from a significant increase in product yield and purity compared to existing chiral separation processes. This work sets up a process design platform to extend the use of this hybrid process to a separation of other mixtures. This novel process especially is a promising alternative for chiral separation of pharmaceutical compounds which include more than fifty percent of approved drugs world-wide. A better performance chiral separation technique contributes to cut the operating cost and to reduce the price of chiral drugs.
40
Elharati, M. A. "Poly(vinyl alcohol) / polyamide thin-film composite membranes". Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2105.
Testo completoAbstract (sommario):
Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: The aim of this study was to modify the surface of polyethersulfone (PES) ultrafiltration (UF) membranes to produce a more hydrophilic membrane by cross-linking poly(vinyl alcohol) (PVA) with sodium tetraborate (Na2B4O7.10H2O) (SB) on the surface. Key preparation factors were identified as PVA molecular weight, concentrations of the PVA and SB, cross-linking reaction time, number of coatings and the mode of coating. The effect of these factors on the membrane performance (salt retention and permeate flux) is discussed. These PVA-SB membranes typically had 11.46% retention and 413.30 L/m2.h flux for a feed containing 2000 ppm NaCl (0.45 MPa, 20°C, 45 – 50 L/h). The coating was shown to be uniform and stable by Fourier transform infrared spectroscopy (FT-IR) analyses. Coating significantly increased hydrophilicity and a maximum flux increase of 500 L/m2.h was reached. Measurements showed a reduced water contact angle and this confirmed the obvious enhancement of surface hydrophilicity. As a control, the role of the PVA base layer without cross-linking and the effects of its drying and heating on the water permeability of the PES-UF membrane were also studied, in order to ascertain maximum treatment conditions. Retention and permeate flux were determined (feed solution: 2000 ppm NaCl, applied pressure 0.45 MPa, 25°C, 45 – 50 L/h). It was found that the heating had the largest effect on the reduction of water permeability and therefore 50°C was the limit for treatment of this specific PES-UF membrane. Thin-film composite (TFC) membranes were prepared by an interfacial polymerization (IP) reaction between a polyfunctional amine and tri- or di-functional carboxylic chloride and then evaluated for their reverse osmosis (RO) performance. The salt retention of the PVA-SB membranes was improved when covering the cross-linked PVA gel sub-layer with a polyamide (PA) layer. However, the permeate flux decreased to below 30 L/m2.h (2000 ppm NaCl, 1 – 2 MPa, 20°C, 45 – 50 L/h). Two TFC membranes made from trimesoyl chloride (TMC) with m-phenylenediamine (MPD) or 2,6-diaminopyridine (DAP) exhibited retentions of 96.71% to 89.65% and fluxes of 10.93 to 27.91 L/m2.h, depending on the type of diamine used, when tested with a 2000 ppm NaCl solution (2 MPa, 25°C, 45 – 50 L/h). Two TFC membranes made from a n ew 2,5-furanoyl chloride (FC) with MPD or DAP exhibited retentions of 34.22% to 58.54% and fluxes of 49.21 to 25.80 L/m2.h, depending on the type of diamine used, when tested with a 2000 ppm NaCl solution (1 MPa, 25°C, 45 – 50 L/h). Novel PVA-SB-DAP-FC membranes made from the DAP with FC had the highest hydrophilicity value and exhibited >58.54% NaCl retention and 25.80 L/m2.h flux, and 75.08% MgSO4 retention and 34.75 L/m2.h flux, when tested with (2000 ppm feed, 1 MPa, 25°C, 45 – 50 L/h). The effect of the chemical structures of the different amines and carboxylic chlorides used on the RO performances of the TFC membranes prepared by two amines reacting with TMC or FC, on the surfaces of the modified asymmetric PES-UF membranes, was investigated. FT-IR and water contact angle determination were used to characterize the chemical structure, morphology and hydrophilicity of the PA layers of the composite membranes. The response surface methodology (RSM) was used to optimize the preparation conditions that had the largest effects on the RO performance of the PVA-SB-DAP-FC membranes. Good membrane performance could be realized particularly by manipulating three variables: DAP concentration, FC concentration and polymerization time (PT). The regression equation between the preparation variables and the performance of the composite membranes was established. Main effects, quadratic effects and interactions of these variables on the composite membrane performance were investigated. The membranes were characterized in terms of pure water permeation (PWP) rate, molecular weight cut off (MWCO), solute separation and flux. Mean pore size (μp) and standard deviation (σp) of the membranes were determined using solute transport data. The results revealed that PVA-SB membranes have almost the same pure water permeation that PES-UF membranes have. The MWCO of the PES-UF membranes decreased from 19,000 to 13,000 Daltons when the membrane was coated with PVA.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie is die modifikasie van die oppervlakte van poliëtersulfoon ultrafiltrasie (PES-UF) membrane om meer hidrofiliese membrane te berei deur die kruisbinding van polivinielalkohol (PVA) met natriumtetraboraat ((Na2B4O7.10H2O) (NaB) op die membraanoppervlakte. Sleutelfaktore in die bereidingsproses is geïdentifiseer, naamlik: PVA molekulêre massa, PVA en NaB konsentrasies, kruisbindingsreaksietyd, die aantal bestrykingslae, en die manier waarop die bestrykingslae aangewend is. Die invloed van hierdie faktore op die membraanontsouting en vloed is ondersoek, en word hier bespreek. Hierdie PVA-NaB membrane het die volgende tipiese resultate getoon: 11.46% ontsouting en 413.30 L/m2.h vloed (Kondisies: 2000 dpm NaCl oplossing, 0.45 MPa toegepaste druk, 20 °C, vloeitempo 45–50 L/h). Die deklaag was uniform en stabiel, soos bepaal d.m.v. FTIR. Die aanwesigheid van die deklaag het die hidrofilisiteit verhoog en 'n maksimum vloed van 500 L/m2.h is behaal. Die waterkontakhoek is ook gemeet; 'n laer waarde het 'n verbetering in die hidrofilisiteit van die oppervlakte bevestig. Die rol van die PVA basislaag, sonder kruisbinding (kontrole), en die effek van uitdroging en verhitting hiervan, is ook bestudeer, om sodoende optimale behandelingskondisies te bepaal. Membraanontsouting en vloed is bepaal (Kondisies: 2000 dpm NaCl oplossing, 0.45 MPa toegepaste druk, 25 °C, vloeitempo 45–50 L/h). Verhitting het die grootste effek gehad op die afname in vloed. Daar is bevind dat 'n maksimum temperatuur van 50°C geskik is vir die behandeling van hierdie spesifieke PES-UF membraan. Dunfilmsaamgestelde (DFS) membrane is berei d.m.v. 'n tussenvlakpolimerisasiereaksie tussen 'n polifunksionele amien en 'n di- of tri-funksionele karbonielchloried, en daarna is die tru-osmose (TO) gedrag bepaal. Die ontsouting van die PVA-NaB membrane was hoër nadat die kruisgebinde PVA jel sub-laag met 'n poliamied (PA) laag bedek is. Die vloed het egter afgeneem, tot onder 30 L/m2.h (Kondisies: 2000 dpm NaCl oplossing, 1–2 MPa toegepaste druk, 20 °C, vloeitempo 45–50 L/h). Twee DFS membrane is berei met trimesoïelchloried (TMC), naamlik met m-fenieldiamien (MFD) of 2,6-diaminopiridien (DAP). Afhangend van die diamien wat gebruik is, is die volgende ontsoutingsresultate en vloede verkry: 96.71% tot 89.65% en 10.93 to 27.91 L/m2.h (Kondisies: 2 000 dpm NaCl oplossing, 2 MPa toegepaste druk, 25 °C, v loeitempo 45–50 L/h). Twee DFS membrane is ook berei met 'n nuwe verbinding, 2,5-furanoïelchloride (FC), en MFD of DAP. Afhangend van die diamien wat gebruik is is die volgende ontsoutingsresultate en vloede behaal: 34.22% tot 58.54% en 49.21 tot 25.80 L/m2.h (Kondisies: 2000 dpm NaCl oplossing, 1 MPa toegepaste druk, 25 °C, vloeitempo 45–50 L/h). Die PVA-NaB-DAP-FC membrane het die hoogste hidrofilisiteit getoon: 58.54% NaCl ontsouting en 25.80 L/m2.h vloed, en 75.08% MgSO4 ontsouting en 34.75 L/m2.h vloed (2000 ppm NaCl oplossing, 1 MPa toegepaste druk, 25 °C, vloeitempo 5–50 L/h). Die invloed van die chemiese struktuur van die verskillende diamiene en karboksielsuurchloriedes wat gebruik is in die bereiding van die DFC membrane op die oppervlakte van die gewysigde PES-UF membrane is in terme van TO ondersoek. FTIR en kontakhoekbepalings is gebruik om die chemiese struktuur, morfologie en hidrofilisiteit van die PA lae van die saamgestelde membrane te bepaal. Die eksperimentele oppervlakte ontwerp metode is gebruik om die bereidingskondisies vir die TO aanwending van die PVA-NaB-DAP-FC membrane te optimiseer. Goeie resultate is verkry deur die volgende veranderlikes te manipuleer: DAP en FC konsentrasies en die tydsduur van die polimerisasie. 'n Regressie-vergelyking tussen die bereidingsverandelikes en die funksionering van die saamgestelde membrane is bepaal. Die volgende is ook ondersoek vir hul effek op die funksionering van die saamgestelde membrane: hoof-effekte, vierkantseffekte, en interaksie tussen veranderlikes. Die eienskappe van die membrane wat bepaal is, is: deurlatingstempo van suiwer water (DSW), molekulêre massa-afsnypunt (MMAP), skeiding van opgeloste sout en vloed. Deurlating van opgeloste sout data is gebruik om gemiddelde poriegrootte (μp) en standaard afwyking (σp) van die membrane te bepaal. Resultate het getoon dat die PVA-NaB membrane amper dieselfde DSW gehad het as die PES-UF membrane. Die MMAP van die PES-UF membrane het afgeneem van 19,000 tot 13,000 Daltons na behandeling met PVA.
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Perera, Dehiwalage Harshani Nimalika. "Thin film composite membranes for desalination". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709429.
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Ji, Jiang. "Fabrication and photochemical surface modification of photoreactive thin-film composite membranes and model development for thin film formation by interfacial polymerization /". *McMaster only, 1996.
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Haryadi, Haryadi Chemistry Faculty of Science UNSW. "Porous hybrid organic-inorganic silica materials: preparation, structural and transport properties". Awarded by:University of New South Wales. School of Chemistry, 2005. http://handle.unsw.edu.au/1959.4/28806.
Testo completoAbstract (sommario):
The aim of this project was to prepare a series of silica materials based on sol-gel processing of alkoxysilanes using glucose and glycerol as templates for potential applications in membrane design for pervaporation. The materials were characterized using structural and dynamic techniques to gain information about the effect of the templates on the formation of micro- and mesoporous silicates. The interaction between templates and silica matrices were investigated using FTIR, Raman Spectroscopy, Solid State NMR Spectroscopy, Physisorption and SEM. Close contact between templates and silica networks was observed by NMR cross polarization studies. The chemistry was then extended to prepare hybrid organic-inorganic silica materials by introducing organic ligands, with glycerol as a template to control the porosity of the hybrid materials. By varying the ligand as well as the template, the physical properties of the gel can be controlled. Composites of hydroxypropylcellulose, HPC, and silica were also prepared and characterized. There was no phase separation during sol-gel processing suggesting HPC was dispersed homogenously in the silica matrices. This was also confirmed by solid state NMR. Temperature dependence showed some indications of conformational change in the HPC within the silicate, above 308K. The transport properties of the hybrid materials were observed by monitoring the diffusion behaviour of water and several selected solvents using Pulsed Field Gradient NMR. The self-diffusion of water and the organic solvents in the hybrid silica materials were two to three orders of magnitude smaller than in the liquid bulk suggesting restricted diffusion at the pore surface. The effect of surface polarity also contributed to water and solvents diffusivities. The temperature dependence of diffusion was useful to derive the activation energy whereas the dependence on NMR observation time provided information on both tortuosity and pore connectivity of the hybrid silica materials. The hybrid silica membranes were prepared by spin coating of polymeric silica sol on top of a macroporous alumina support after being occluded by colloidal silica. It was then used for pervaporation of water ethanol mixtures. The results implied that separation factor increased as the temperature increased. However permeate fluxes were less affected.
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Garcia-Aleman, Jesus Dickson James M. "Mathematical modeling of the pressure-driven performance of McMaster pore-filled membranes /". *McMaster only, 2002.
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Lau, Pui Sze. "Influence of membrane chemistry on transport property /". View Abstract or Full-Text, 2002. http://library.ust.hk/cgi/db/thesis.pl?CENG%202002%20LAUP.
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Lai, Sau Man. "Fabrication of zeolite microsystems and their applications /". View Abstract or Full-Text, 2003. http://library.ust.hk/cgi/db/thesis.pl?CENG%202003%20LAI.
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Leung, Adrian Yat Lai. "Fabrication and properties of zeolitic microchemical systems /". View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CENG%202004%20LEUNG.
Testo completoAbstract (sommario):
Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 140-152). Also available in electronic version. Access restricted to campus users.
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Tabarizadeh, Elham. "PDMS-based membranes for dehydration of Triethylene glycol using pervaporation technology". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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This thesis is relying on membrane separation technology and it seeks to find an appropriate membrane to use in pervaporation setup for the subsea regeneration of triethylene glycol (TEG) in natural gas dehydration.
Although some effort have been spent on membrane absorption for gas dehydration with glycols, there is still a lack of information about TEG dehydration using pervaporation technology with different membranes, therefore experimental data is needed to assess the feasibility of using membrane pervaporation for regeneration of TEG for subsea condition. In the present work, an experimental study of dehydration of TEG with pervaporation technology has been carried out using a composite membrane with the porous support of polysulfone (PSF) coated with a dense layer of Polydimethylsiloxane (PDMS).
The membrane was characterized in terms of compatibility to TEG, chemical analysis identification using Fourier Transform Infrared (FTIR) spectroscopy, morphology and surface properties with scanning electron microscopy (SEM), and contact angle measurements. Furthermore, a method for analyzing low concentrations of TEG in aqueous solutions was used with gas chromatography (GC) as this was vital to the pervaporation study. The criteria for choosing PDMS polymer was the minimum TEG uptake, high flux, and lower price.
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Patterson, Brian Clay. "Viologen-mediated electron transfer across dihexadecylphosphate bilayer membranes /". Full text open access at:, 1990. http://content.ohsu.edu/u?/etd,238.
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Dehaney-Steven, Zachary Alexander. "Development and testing of mixed-phase oxygen transport membranes". Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/16807.
Testo completoAbstract (sommario):
Perhaps mankind's most urgent challenge at present is anthropogenic climate change, with the associated sea-level rise and desertification set to produce major losses of arable land and living space, as well as loss of life. The key to preventing the worst effects of AGW lies in limiting humanity's emissions of the greenhouse gas carbon dioxide, of which the vast majority comes from the burning of fossil fuels such as coal, oil and natural gas. However, fossil fuels are embedded in all of the world's economies, responsible for almost all of the provision of electrical power and transport, making the sizable reductions required in the timescale necessary somewhat impractical. One solution lies in Carbon Capture and Storage (CCS), which involves, in one incarnation, the combustion of fossil fuels in pure oxygen, simplifying the processing and storage of the carbon dioxide produced. There is potential for very high process efficiencies if oxygen is provided by Oxygen Transport Membranes (OTM). This thesis is concerned with the development of membranes and test procedures for mixed-phase OTM, which typically consist of a dense, gastight layer of perovskite and fluorite phases. An inactive support layer may also be present. The surface area, and therefore surface exchange of either side is improved by the addition of exchange layers to either side. Oxide ion migration is accomplished by applying a pO2 differential to the membrane at high temperature. Causes and mechanisms for degradation are not fully understood, and there is potential to improve oxygen flux. One way to achieve this is by the use of very thin, supported membranes, and this thesis demonstrates that such membranes can be fabricated with well-understood manufacturing processes. Another method of improving oxygen flux is by the use of catalysts on the exchange layers of the membrane. The most popular method of introducing 6 catalysts to an exchange layer or electrode involves impregnation of a metal salt into a ceramic backbone, followed by reduction to yield a catalytically active phase. However, this process is wasteful of catalyst, labour-intensive and control of the distribution of catalyst is difficult or impossible. An alternative exists, where metals doped into a perovskite migrate to the surface and form nanoparticles on exposure to a sufficiently high temperature and reducing atmosphere, and this thesis demonstrates the benefits of using such an approach. Improvements in oxygen flux of up to a factor of 7 over an undoped perovskite exchange layer have been demonstrated. The conductivity and crystal structures of (La0.8Sr0.2)0.95Cr0.5Fe0.5O3-δ and (Sc2O3)0.19(CrO2)0.01(ZrO2)0.789O1.94 under oxidising and reducing atmospheres at high temperatures have been evaluated using neutron powder diffraction and a novel in-situ rig, demonstrating that the OTM composition is a p-type conductor, and quantifying the effect of oxygen stoichiometry on conductivity and unit cell parameters.