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1
Bighane, Neha. "Novel silica membranes for high temeprature gas separations." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43732.
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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.
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Ma, Canghai. "Optimization of asymmetric hollow fiber membranes for natural gas separation." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43700.
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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.
3
Kiyono, Mayumi. "Carbon molecular sieve membranes for natural gas separations." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42798.
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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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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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Bae, Tae-Hyun. "Engineering nanoporous materials for application in gas separation membranes." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42712.
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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.
6
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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Diamond, Geoffrey Graham. "Organically templated inorganic membranes for gas separation." Thesis, University of Warwick, 2001. http://wrap.warwick.ac.uk/3071/.
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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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Kim, Wun-Gwi. "Nanoporous layered oxide materials and membranes for gas separations." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47591.
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The overall focus of this thesis is on the development and understanding of
nanoporous layered silicates and membranes, particularly for potential applications in gas
separations. Nanoporous layered materials are a rapidly growing area of interest, and
include materials such as layered zeolites, porous layered oxides, layered
aluminophosphates, and porous graphenes. They possess unique transport properties that
may be advantageous for membrane and thin film applications. These materials also have
very different chemistry from 3-D porous materials due to the existence of a large,
chemically active, external surface area. This feature also necessitates the development of
innovative strategies to process these materials into membranes and thin films with high
performance.
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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.
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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.
10
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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Chen, Chien-Chiang. "Thermally crosslinked polyimide hollow fiber membranes for natural gas purification." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45848.
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Robust industrially relevant membranes for CO₂ removal from aggressive natural gas feed streams were developed and characterized. Asymmetric hollow fiber membranes with defect-free selective skin layers on an optimized porous support substructure were successfully spun and subsequently stabilized by covalent crosslinking within the economical membrane formation process. Thermal treatment conditions, which promote sufficient crosslinking without introducing defects or undesired substructure resistance, were identified. It was found that crosslinking improves membrane efficiency and plasticization resistance as well as mechanical strength of fibers. The capability to maintain attractive separation performance under realistic operating conditions and durability against deleterious impurities suggests that the crosslinked fibers have great potential for use in diverse aggressive applications, even beyond the CO₂/CH₄ example explored in this work.
12
Esekhile, Omoyemen Edoamen. "Mixed matrix membranes for mixture gas separation of butane isomers." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42929.
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The goal of this project was to understand and model the performance of hybrid inorganic-organic membranes under realistic operating conditions for hydrocarbon gas/vapor separation, using butane isomers as the model vapors and a hybrid membrane of 6FDA-DAM-5A as an advanced separation system.
To achieve the set goal, three objectives were laid out. The first objective was to determine the factors affecting separation performance in dense neat polymer. One main concern was plasticization. High temperature annealing has been reported as an effect means of suppressing plasticization. A study on the effect of annealing temperature was performed by analyzing data acquired via sorption and permeation measurements. Based on the findings from this study, a suitable annealing temperature was determined. Another factor studied was the effect of operating temperature. In deciding a suitable operating temperature, factors such as its possible effect on plasticization as well as reducing heating/cooling cost in industrial application were considered.
Based on the knowledge that industrial applications of this membrane would involve mixture separation, the second objective was to understand and model the complexity of a mixed gas system. This was investigated via permeation measurements using three feed compositions. An interesting transport behavior was observed in the mixed gas system, which to the best of our knowledge, has not been observed in other mixed gas systems involving smaller penetrants. This mixed gas transport behavior presented a challenge in predictability using well-established transport models. Two hypotheses were made to explain the observed transport behavior, which led to the development of a new model termed the HHF model and the introduction of a fitting parameter termed the CAUFFV fit. Both the HHF model and CAUFFV fit showed better agreement with experimental data than the well-established mixed gas transport model.
The final objective was to explore the use of mixed matrix membranes as a means of improving the separation performance of this system. A major challenge with the fabrication of good mixed matrix membranes was the adhesion of the zeolite particle with the polymer. This was addressed via sieve surface modification through a Grignard treatment process. Although a Grignard treatment procedure existed, there was a challenge of reproducibility of the treatment. This challenge was addressed by exploring the relationship between the sieves and the solvent used in the treatment, and taking advantage of this relationship in the Grignard treatment process. This study helped identify a suitable solvent, which allowed for successful and reproducible treatment of commercial LTA sieves; however, treatment of lab-made sieves continues to prove challenging. Based on improved understanding of the Grignard treatment reaction mechanism, modifications were made to the existing Grignard treatment procedure, resulting in the introduction of a "simplified" Grignard treatment procedure. The new procedure requires less control over the reaction process, thus making it more attractive for industrial application.
Permeation measurements were made using mixed matrix membranes in both single and mixed gas systems. Selectivity enhancements were observed under both single and mixed gas systems using sieve loadings of 25 and 30wt%. The Maxwell model was used to make predictions of mixed matrix membrane performance. Although the experimental results were not in exact agreement with Maxwell predictions, the observed selectivity enhancement was very encouraging and shows potential for future application. Recommendations were made for future study of this system.
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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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Omole, Imona C. "Crosslinked polyimide hollow fiber membranes for aggressive natural gas feed streams." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/26591.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Dr. William J. Koros; Committee Member: Dr. Amyn Teja; Committee Member: Dr. Christopher W. Jones; Committee Member: Dr. Haskell W. Beckham; Committee Member: Dr. Stephen J. Miller. Part of the SMARTech Electronic Thesis and Dissertation Collection.
15
Senn, Simon Charles. "The preparation and characterization of hollow fibre membranes for gas separation." Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/405/.
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A dry-jet wet-spinning process developed industrially for the preparation of hollow fibre membranes suitable for gas separation applications, has been reproduced on a laboratory scale. Polysulphone hollow fibres were spun from a variety of solvents and their gas transport properties were characterized using equipment built during the course of the research. The phase inversion process of membrane formation was studied in order that the best morphological structure could be produced. The spinning parameters were studied to establish their influence on the fibre dimensions. Further relationships were then sought between the gas transport properties and the fibre dimensions and spinning parameters. The behaviour of the membranes to both single gases and gas mixtures was studied. Both the permeation rate constants and the separation factors determined from the mixture permeation were found to be lower than the values predicted from the single gas permeation experiments. A model was developed to help understand the competitive nature of the adsorption-diffusion process and explain the differences in values recorded from the single gas and mixture studies. Experiments aimed at improving membrane performance were based on modification of the already established polysulphone hollow fibre. Modification of the selective surface layer of the hollow fibre membranes was considered to be the best approach. Coating of the fibres, other than to repair damage to the skin layer, was found to result in too large a decrease in permeability. Sulphonation of the surface layer was achieved using sulphur trioxide, although little improvement in the membrane performance was recorded. The sulphonation experiment results were, however, sufficiently encouraging to recommend future work.
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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.
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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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Jee, Sang Eun. "The effect of pore dimension of zeolites on the separation of gas mixtures." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33893.
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We examined the effect of the pore dimension of zeolites on the separation of gas mixtures using atomistic simulation methods. We studied two categories of the zeolites with small pores: pore modified silicalite for H₂/CH₄separation and small pore silica zeolites for CO₂/CH₄separation. The effect of pore modification of silicalite on the H₂/CH₄separation was examined. Under some degrees of surface modification, the CH₄flux was reduced much more than the H₂flux, resulting in high ideal selectivities. The use of small pore zeolites for CO₂/CH₄separations was studied. In DDR, we showed that CO₂diffusion rates are only weakly affected by the presence of CH₄, even though the latter molecules diffuse very slowly. Consequently, therefore, the permeance of CO₂in the equimolar mixtures is similar to the permeance for pure CO₂, while the CH₄permeance in the mixture is greatly reduced relatively to the pure component permeance. The calculated CO₂/CH₄separation selectivities are higher than 100 for a wide range of feed pressure, indicating excellent separation capabilities of DDR based membranes. Inspired by the observation in DDR we also examined the separation capabilities of 10 additional pure silica small pore zeolites for CO₂/CH₄separations. From these considerations, we predict that SAS, MTF and RWR will exhibit high separation selectivities because of their very high adsorption selectivities for CO₂over CH₄. CHA and IHW, which have similar pore structures to DDR, showed comparable separation selectivities to DDR because of large differences in the diffusion rates of CO₂and CH₄.
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Vaughn, Justin. "Development and evaluation of aromatic polyamide-imide membranes for H₂S and CO₂ separations from natural gas." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47576.
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Over the past decade, membrane based gas separations have gained traction in industry as an attractive alternative to traditional thermally based separations due to their potential to offer lower operational and capital expenditures, greater ease of operation and lower environmental impact. As membrane research evolves, new state-of-the-art membrane materials as well as processes utilizing membranes will likely be developed. Therefore, their incorporation into existing thermally based units as a debottlenecking step or as a stand-alone separation unit is expected to become increasingly more common. Specifically for natural gas, utilization of smaller, more remote natural gas wells will require the use of less equipment intensive and more flexible separation technologies, which precludes the use of traditional, more capital and equipment intensive thermally based units.
The use of membranes is, however, not without challenges. Perhaps the most important hurdle to overcome in membrane development for natural gas purification is the ability to maintain high efficiency in the presence of harsh feed components such as CO₂ and H₂S, both of which can swell and plasticize polymer membranes. Additionally, as this project demonstrates, achievement of similarly high selectivity for both CO₂ and H₂S is challenged by the different governing factors that control their transport through polymeric membranes. However, as others have suggested and shown, as well as what is demonstrated in this project, when CO₂ is the primary contaminant of interest, maintaining high CO₂/CH₄ efficiency appears to be more important in relation to product loss in the downstream. This work focuses on a class of fluorinated, glassy polyamide-imides which show high plasticization resistance without the need for covalent crosslinking. Membranes formed from various polyamide-imide materials show high mixed gas selectivities with adequate productivities when subjected to feed conditions that more closely resemble those that may be encountered in a real natural gas well. The results of this project highlight the polyamide-imide family as a promising platform for future membrane material development for materials aimed at aggressive natural gas purifications due to their ability to maintain high selectivities under aggressive feed conditions without the need for extensive stabilization methods.
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Zou, Jian. "Carbon dioxide-selective membranes and their applications in hydrogen processing." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1173296419.
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Mahajan, Rajiv. "Formation, characterization and modeling of mixed matrix membrane materials /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004329.
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Wang, Lei. "Cyclic membrane gas separation processes." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0291/document.
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Ce travail traite une investigation systématique des performances du procédé membranaire cyclique par séparation gazeuse. Premièrement, l'état de l'art du procédé membranaire cyclique, les problèmes techniques et la modélisation du transfert à travers la membrane ont été exposés. Deuxièmement, les études théoriques et expérimentales existantes sur le procédé cyclique sont passées en revue. Selon la durée de pression haute et sa fraction dans un cycle, ce genre d'opération est divisé en deux classes: classes courte et longue. D'après cette classification, une analyse systématique de l'intérêt potentiel de la classe courte par rapport aux performances d'une opération en régime permanent a été accomplie par des simulations et optimisations numériques. Par ailleurs, afin d'améliorer la performance, l'usage du MMM dans un tel procédé a été discuté. En parallèle à l'étude sur la classe courte, une nouvelle conception du procédé cyclique de classe longue a été proposée. Les avantages spectaculaires par rapport aux procédés membranaires classiques ont été mis en évidence à l'aide de nos simulations et optimisations. Finalement, une validation expérimentale a été effectuée afin de fournir un support solide à cette nouvelle conceptionThis study deals with a systematic investigation of the performance of cyclic membrane gas separation processes. First, a state of the art of membrane separation processes, including material challenges and mass transfer modeling issues is proposed. In a second step, a review of the different theoretical and experimental studies performed on cyclic processes is reported. With respect to the length of the high pressure stage and its fraction in one cycle, these operations are classified into short and long classes. Based on this classification, a systematic analysis of the potential interest of short class compared to steady-state operation performances has been achieved by means of numerical simulation and optimization. In order to improve the performance, the use of MMM in such a process has been further discussed. In parallel with the short class study, a design of novel long class has been proposed. Spectacular advantages with respect to classical membrane-based processes have been highlighted by means of our simulation and optimization studies. Finally, an experimental verification has been performed in order to provide a solid support to this novel process
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Shehu, Habiba. "Innovative hydrocarbons recovery and utilization technology using reactor-separation membranes for off-gases emission during crude oil shuttle tanker transportation and natural gas processing." Thesis, Robert Gordon University, 2018. http://hdl.handle.net/10059/3129.
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The increase in greenhouse gas (GHG) concentrations in the atmosphere, as well as the high rate of depletion of hydrocarbon-based resources have become a global concern. A major source of emissions of hydrocarbon vapours occur during loading and offloading operations in crude oil shuttle tanker transportation. The emitted gases have a typical composition of 60 % N2, 10 % CO2, 5% O2, 5 % C3H8, 10% CH4, 5% C2H6 and 5 % higher hydrocarbons. As a result, various methods aimed to add value to GHG to produce valuable fuels and chemical feedstock are being developed. This work incorporates the use of silica, polyurethane/zeolite and y-type zeolite membrane on an alumina support to selectively permeate methane and carbon dioxide from inert gases and higher hydrocarbons. The recovered gas is upgraded by dry reforming reactions employing rhodium/alumina membrane incorporated into a shell and tube reactor. Mixed gas permeation tests have been carried out with the permeate and feed gases sent to the online gas chromatograph (GC) equipped with a mass spectrometry (MS) detector and an automated 6-port gas sampling valve with a 30 mm HP- Plot Q column. The question is what mesoporous membrane can be highly selective for the separation of methane and carbon dioxide from inert gases and higher hydrocarbons, and what is the effect of temperature and feed gas pressure on the conversion of separated gases? Characterisation of the modified membranes was carried out using nitrogen physisorption measurements and showed the hysteresis isotherms corresponding to type IV and V, which is indicative of a mesoporous membrane. The surface area and the pore size were determined using the Barrett, Joyner, Halenda (BJH) desorption method, which showed the silica membrane had a larger surface area (10.69 m2 g-1) compared to zeolite (0.11 m2 g-1) and polyurethane/zeolite membrane (0.31 m2 g-1). Fourier Transform Infrared spectroscopy, Scanning Electron Microscope and Energy Dispersive X-ray Analysis confirmed the asymmetric deposition of silica, polyurethane, rhodium and zeolite crystals in the matrix of the alumina support. Single gas permeation tests showed that the synthesised y-type zeolite membrane at 293 K had a CH4/C3H8 selectivity of 3.11, which is higher than the theoretical value of 1.65. The permeating CH4 and C3H8 flux at 373 K and a pressure of 1 x 105 Pa was 0.31 and 0.11 mol s-1 m-2 respectively proving that zeolite has molecular sieving mechanism for separation of methane and propane. The silica membrane exhibited higher effectiveness for the separation of CO2 than the other membranes. For methane dry reforming using a supported rhodium membrane, an increase of the reaction temperature from 973 K to 1173 K showed an increase in conversion rate of CO2 and CH4 from less than 20% to over 90% while increasing the gas hourly space velocity (GHSV) did not have a noticeable effect. The study revealed the high potential of the zeolite and rhodium membrane for gas separation and dry reforming reactions concept in creating value-added carbon-based products from CO2 and CH4.
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Maxwell, Taylor Patrick. "Passive Gas-Liquid Separation Using Hydrophobic Porous Polymer Membranes: A Study on the Effect of Operating Pressure on Membrane Area Requirement." UNF Digital Commons, 2012. http://digitalcommons.unf.edu/etd/351.
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The use of hydrophobic porous polymer membranes to vent unwanted gas bubbles from liquid streams is becoming increasingly more common in portable applications such as direct methanol fuel cells (DMFCs) and micro-fluidic cooling of electronic circuits. In order for these portable systems to keep up with the ever increasing demand of the mobile user, it is essential that auxiliary components, like gas-liquid separators (GLS), continue to decrease in weight and size. While there has been significant progress made in the field of membrane-based gas-liquid separation, the ability to miniaturize such devices has not been thoroughly addressed in the available literature. Thus, it was the purpose of this work to shed light on the scope of GLS miniaturization by examining how the amount porous membrane required to completely separate gas bubbles from a liquid stream varies with operating pressure. Two membrane characterization experiments were also employed to determine the permeability, k, and liquid entry pressure (LEP) of the membrane, which provided satisfying results. These parameters were then implemented into a mathematical model for predicting the theoretical membrane area required for a specified two-phase flow, and the results were compared to experimental values. It was shown that the drastically different surface properties of the wetted materials within the GLS device, namely polytetrafluoroethylene (PTFE) and acrylic, caused the actual membrane area requirement to be higher than the theoretical predictions by a constant amount. By analyzing the individual effects of gas and liquid flow, it was also shown that the membrane area requirement increased significantly when the liquid velocity exceeded an amount necessary to cause the flow regime to transition from wedging/slug flow to wavy/semi-annular flow.
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Crawford, Phillip Grant. "Zeolite membranes for the separation of krypton and xenon from spent nuclear fuel reprocessing off-gas." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50383.
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The goal of this research was to identify and fabricate zeolitic membranes that can separate radioisotope krypton-85 (half-life 10.72 years) and xenon gas released during spent nuclear fuel reprocessing. In spent nuclear fuel reprocessing, fissionable plutonium and uranium are recovered from spent nuclear fuel and recycled. During the process, krypton-85 and xenon are released from the spent nuclear fuel as process off-gas. The off-gas also contains NO, NO2, 129I, 85Kr, 14CO2, tritium (as 3H2O), and air and is usually vented to the atmosphere as waste without removing many of the radioactive components, such as 85Kr. Currently, the US does not reprocess spent nuclear fuel. However, as a member of the International Framework for Nuclear Energy Cooperation (IFNEC, formerly the Global Nuclear Energy Partnership), the United States has partnered with the international nuclear community to develop a “closed” nuclear fuel cycle that efficiently recycles all used nuclear fuel and safely disposes all radioactive waste byproducts. This research supports this initiative through the development of zeolitic membranes that can separate 85Kr from nuclear reprocessing off-gas for capture and long-term storage as nuclear waste. The implementation of an 85Kr/Xe separation step in the nuclear fuel cycle yields two main advantages. The primary advantage is reducing the volume of 85Kr contaminated gas that must be stored as radioactive waste. A secondary advantage is possible revenue generated from the sale of purified Xe.
This research proposed to use a zeolitic membrane-based separation because of their molecular sieving properties, resistance to radiation degradation, and lower energy requirements compared to distillation-based separations. Currently, the only commercial process used to separate Kr and Xe is cryogenic distillation. However, cryogenic distillation is very energy intensive because the boiling points of Kr and Xe are -153 °C and -108 °C, respectively. The 85Kr/Xe separation step was envisioned to run as a continuous cross-flow filtration process (at room temperature using a transmembrane pressure of about 1 bar) with a zeolite membrane separating krypton-85 into the filtrate stream and concentrating xenon into the retentate stream. To measure process feasibility, zeolite membranes were synthesized on porous α-alumina support discs and permeation tested in dead-end filtration mode to measure single-gas permeance and selectivity of CO2, CH4, N2, H2, He, Ar, Xe, Kr, and SF6. Since the kinetic diameter of krypton is 3.6 Å and xenon is 3.96 Å, zeolites SAPO-34 (pore size 3.8 Å) and DDR (pore size 3.6 Å) were studied because their pore sizes are between or equal to the kinetic diameters of krypton and xenon; therefore, Kr and Xe could be separated by size-exclusion. Also, zeolite MFI (average pore size 5.5 Å) permeance and selectivity were evaluated to produce a baseline for comparison, and amorphous carbon membranes (pore size < 5 Å) were evaluated for Kr/Xe separation as well.
After permeation testing, MFI, DDR, and amorphous carbon membranes did not separate Kr and Xe with high selectivity and high Kr permeance. However, SAPO-34 zeolite membranes were able to separate Kr and Xe with an average Kr/Xe ideal selectivity of 11.8 and an average Kr permeance of 19.4 GPU at ambient temperature and a 1 atm feed pressure. Also, an analysis of the SAPO-34 membrane defect permeance determined that the average Kr/Xe selectivity decreased by 53% at room temperature due to unselective defect permeance by Knudsen diffusion. However, sealing the membrane defects with polydimethylsiloxane increased Kr/Xe selectivity by 32.8% to 16.2 and retained a high Kr membrane permeance of 10.2 GPU at ambient temperature. Overall, this research has shown that high quality SAPO-34 membranes can be consistently fabricated to achieve a Kr/Xe ideal selectivity >10 and Kr permeance >10 GPU at ambient temperature and 1 atm feed pressure. Furthermore, a scale-up analysis based on the experimental results determined that a cross-flow SAPO-34 membrane with a Kr/Xe selectivity of 11.8 and an area of 4.2 m2 would recover 99.5% of the Kr from a 1 L/min feed stream containing 0.09% Kr and 0.91% Xe at ambient temperature and 1 atm feed pressure. Also, the membrane would produce a retentate stream containing 99.9% Xe. Based on the SAPO-34 membrane analysis results, further research is warranted to develop SAPO-34 membranes for separating 85Kr and Xe.
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Bhandari, Dhaval Ajit. "Hollow fiber sorbents for the desulfurization of pipeline natural gas." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42838.
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Pipeline natural gas is the primary fuel of choice for distributed fuel cell-based applications. The concentration of sulfur in odorized natural gas is about 30 ppm, with acceptable levels being <1 ppm for catalyst stability in such applications. Packed bed technology for desulfurization suffers from several disadvantages including high pressure drop and slow regeneration rates that require large unit sizes.
We describe a novel Rapid Temperature Swing Adsorption (RTSA) system utilizing hollow fibers with polymer 'binder', impregnated with high loadings of sulfur selective sorbent 'fillers'. Steam and cooling water can be utilized to thermally swing the sorbent during the regeneration cycles. An impermeable, thin polymer barrier layer on the outside of fiber sorbents allows only thermal interactions with the regeneration media, thereby promoting consistent sorption capacity over repeated cycles. A simplified flow pattern minimizes pressure drop, porous core morphology maximizes sorption efficiencies, while small fiber dimensions allows for rapid thermal cycles.
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Bai, He. "High temperature proton-exchange and fuel processing membranes for fuel cells and other applications." Columbus, Ohio : Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1204732417.
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Yahia, Marei Abdelrahim Mohamed. "Bio(molecular) control of selective ion transport, gas separation and catalytic enzyme-based reactions using functionalized membranes." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS251/document.
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Différents travaux de recherche ont été décrits dans cette thèse. Les travaux de recherche peuvent être résumés comme suit. Le premier chapitre a porté sur l'identification d’inhibiteurs puissants efficaces vis-à-vis de de l'isoenzyme anhydrase carbonique humaine I (hCAI). Considérant l'importance pharmacologique de trouver des inhibiteurs (CAIs) et des activateurs (AACs) sélectifs aux isoformes de l’anhydrase carbonique ), l'anhydrase carbonique humaine I (hCAI) a été confrontée en parallèle à diverses bibliothèques dynamiques constitutionnelles (CDL). Dans le deuxième chapitre, des réseaux constitutionnels dynamiques ont été préparés sous forme de systèmes membranaires liquides et solides agissant comme un réseau pour le transport spécifique des ions lanthanides. Le transport est basé sur la capacité de complexation des lanthanides (La + 3, Lu + 3, Eu + 3) avec les groupes polyéther fonctionnels situés dans les matériaux membranaires. Dans le troisième chapitre, l'approche proposée consiste en l'utilisation de membranes liquides ioniques supportées (SILMs) comprenant deux enzymes différentes de l'anhydrase carbonique, l’enzyme thermo-résistante SspCA et l'enzyme bovine-CA, qui catalysent la réaction de conversion réversible du CO2 en bicarbonate en favorisant la force motrice vers le transport de CO2. La stabilité des membrane, leur perméabilité vis-à-vis de CO2 et de N2 ainsi que la sélectivité idéale (CO2 / N2) ont été déterminées pour les membranes développées. Le quatrième chapitre porte sur la synthèse et la caractérisation de membranes polymères denses pour une application en séparation de gaz. Les mesures de perméabilité aux gaz des membranes polymères synthétisées ont montré que la perméabilité de CO2 est supérieure à celle des autres gaz testés (CH4 et N2). Dans le dernier chapitre, des membranes de PVDF ont été fonctionnalisées avec une enzyme, la phosphotriestérase (PTE), selon deux méthodes différentes pour construire un réacteur à membrane biocatalytique (BMR) avec pour finalité la bioconversion et la séparation sélective du substrat paraoxon. La première méthode met en œuvre une dispersion réversible de nanoparticules magnétiques de PTE qui est immobilisée à la surface de la membrane de PVDF sous l’effet d'un champ magnétique externe. A l’inverse, la seconde méthode porte sur le greffage chimique de l'enzyme PTE, après modification de la surface de la membrane de PVDF native (DAMP-GA-enzymatique). Les deux techniques d'immobilisation d'enzymes ont montré une bonne efficacité et une sensibilité à l'égard de la bioconversion du paraoxon dans les différentes conditions appliquées dans un réacteur à membrane biocatalytique (BMR).De façon globale, les concepts développés dans ce travail de thèse permettront d’ouvrir de nouvelles pistes de recherche allant vers le développement d'une membrane polymère sélective au transport d’ions, de gaz mais aussi active dans les réactions catalytiques enzymatiques grâce à un contrôle bio-moléculaire au niveau des matériaux membranairesDifferent research works have been described in this thesis. The research works can be summarized as the following. The first chapter deals with the identification of effective potent inhibitors for the human carbonic anhydrase I (hCAI) isozyme. Considering the pharmacological importance to find selective CA inhibitors (CAIs) and CA activators (CAAs), human carbonic anhydrase I (hCAI) has been subjected to a parallel screening of various constitutional dynamic libraries (CDL). In the second chapter, constitutional dynamic networks have been used in liquid and solid membrane systems as a carrier network for transporting lanthanides. The transport is based on the complexing ability of lanthanides metals (La+3, Lu+3, and Eu+3) with the functional polyether groups in the membrane materials. In the third chapter, the proposed approach consists in using supported ionic liquid membranes (SILMs) comprising two different carbonic anhydrase enzymes, the thermo-resistant SspCA enzyme and the Bovine-CA enzyme, which catalyze the reaction of reversible conversion of CO2 to bicarbonate, enhancing the driving force for CO2 transport. Membrane stability, CO2 and N2 permeability and (CO2/N2) ideal selectivity were determined for the membranes developed. In the fourth chapter, the research work consists in the synthesis and characterization of dense polymeric membranes for gas separation application. The gas permeability measurements for the synthesized polymeric membranes showed that the permeability of CO2 is higher than other used gases (N2 and CH4). In the last chapter, two different methods of PVDF membrane functionalization with a phosphotriesterase (PTE) enzyme have been developed to construct biocatalytic membrane reactor (BMR) for bioconversion and selective separation of paraoxon substrate. The first method employs reversible dispersion of magnetic nanoparticle immobilized with PTE using an external magnetic field on the surface of native PVDF membrane. On the contrary, the second method comprises chemical grafting of the PTE enzyme, after surface modification of the native PVDF membrane (DAMP-GA-Enzyme). Both methods of enzyme immobilization showed good efficiency and sensitivity towards the bioconversion of paraoxon substrate at different conditions applied in a biocatalytic membrane reactor (BMR).In general, the concepts developed in this thesis research work will help bring new tracks on the way to the development of a polymeric membrane for selective ion and gas separation but also for selective catalytic reaction under bio(molecular) control
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Tilli, Paola. "Production, characterization and modeling of hollow fiber membranes for biogas purification." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Find full textAbstract:
One type of technology for biogas purification which has experienced substantial growth during past decades is membrane-based technology which presents the advantage of high energy efficiency, simplicity in design and environmental compatibility. The market for CO₂ is dominated by polymeric membranes due to their relatively low manufacturing cost. In this work, the performance of different P84 hollow fibers membranes for CO₂/CH₄ separation is investigated. Different spinning parameters are studied on their effect on gas separation performance of the produced fibers. The attention is focused on air gap length and spinning temperature, since they both affect the formation of the selective layer during the spinning process. Scanning Electron Microscopy (SEM) is used to investigate the morphological characteristics of the developed fibers. Permeation rates of CO₂ and N₂ are measured using the pressure increase method. The achieved ideal selectivity was 30/40 for CO₂/N₂ separation, while permeances are quite low. The permeance of CO₂ through asymmetric hollow fibers increases with pressure because of plasticization. Both gases permeance increases by increasing the air gap and higher spinning temperatures lead to lower permeances. Finally, NE-LF model is used to calculate CO₂ and CH₄ solubility and CO₂/CH₄ solubility selectivity in P84. Large deviation from ideal conditions is predicted underlining a marked competition which affects more CH₄ than CO₂ and results in a real solubility selectivity higher than the ideal one. By considering that real mixed gas perm-selectivity generally presents negative deviation, it follows that diffusivity of CH₄ in P84 is enhanced in presence of CO₂ lowering the diffusivity-selectivity.
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Gu, Yingying. "Membranes polymères fonctionnalisées par des poly(liquide ionique)s et des nanoparticules de palladium : applications au captage de CO2 et aux membranes catalytiques." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30157/document.
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Des membranes supports en polymère ont été photo-greffées par des poly(liquide ionique)s (polyLIs) à base d'imidazolium. Les polyLIs permettent de séparer le CO2 d'autres gaz et de stabiliser des nanoparticules. Dans le cas du captage de CO2, les expériences montrent qu'une couche fine homogène de gel réticulé en polyLI gonflé par du liquid ionique (LI) est obtenue sur la surface de fibres creuses. Les fibres ainsi obtenues ont montré des perméances au CO2 plus élevées (600-700 GPU) que des membranes commerciales et des sélectivités de CO2/N2 comparables (13 et 17). Dans le cas de membranes catalytiques, des nanoparticules de palladium (NPPd) servant de catalyseur ont été immobilisées en forte concentration locale au sein d'une couche de polyLI greffée à la surface de membranes. La réactivité des membranes catalytiques a été testée en configuration de contacteur traversé sur différentes réactions (couplage croisé C-C, hydrogénation, etc). Une conversion totale est obtenue pour des temps de séjours de quelques secondes, sans aucun sous-produit formé. Comparée aux NPPd colloïdaux dans un réacteur en batch, la membrane catalytique accélère les réactions d'environ 2000 fois en terme de temps de réaction sans perte de NPPd; la sélectivité est aussi accrue. Le réacteur membranaire catalytique a été modélisé afin d'obtenir les profils de concentration et de température et une meilleure compréhension des performances obtenues. Les membranes catalytiques se révèlent isothermes et les constantes cinétiques sont calculées. Enfin, les capacités de production de ces membranes catalytiques à une échelle industrielle sont estimées à environ 3 t/(hm3) pour le couplage de SuzukiPolymeric support membranes were modified via photo-grafting by poly(ionic liquid)s (polyILs), featuring in the capability to separate CO2 from other gases and to stabilize metallic nanoparticles (MNPs). For CO2 capture, a thin polyIL-IL gel layer was homogenously coated on support hollow fibers. The composite fibers show high CO2 permeance and reasonable CO2/N2 selectivity. For the catalytic membrane, palladium NPs were generated inside a grafted polyLI layer. Compared to colloidal palladium system in a batch reactor, the catalytic membrane, as a contactor membrane reactor, is more efficient in terms of reaction time (ca. 2000 times faster), selectivity and MNP retainability. Theoretical study on reactor modeling, concentration & temperature profiles, and production capacity was done for an overall understanding of the catalytic membrane
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Li, Kang. "Gas separation using membranes." Thesis, University of Salford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292882.
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Pengilley, Christine. "Membranes for gas separation." Thesis, University of Bath, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.678858.
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The effective separation of ammonia from the synthesis loop in ammonia synthesis plants is an important step in its manufacture. This work presents the use of nanocomposite MFI zeolite membranes prepared by a pore-plugging method for this separation process. Performance of a zeolite membrane is highly dependent on the operating conditions. Therefore, the influences of differential pressure, temperature, sweep gas flow, feed gas flow and gas composition are studied experimentally. Transport of NH3 in this membrane is by surface diffusion in the intracrystalline (zeolite) pores in parallel with capillary condensation in the intercrystalline (non-zeolite) pores. The separation of NH3 from a mixture with H2 and N2 is by preferential adsorption of NH3, which hinders the permeation of weakly adsorbed H2 and N2. Differential pressure has only relatively small effects in the pressure range 300kPa – 1550kPa. Increase in sweep flow rate has little effect on NH3 gas permeance, but H2 and N2 permeances increase thereby decreasing the selectivities. Increase in feed flowrate also has little effect on NH3 permeance. However, the N2 and H2 permeances increase and there is a subsequent decrease in selectivities. Membrane performance was found to be highly dependent on temperature. NH3 permeance in the mixture increases linearly with temperature. NH3 selectivity was found to increase with temperature up to 353K after which it starts to decrease due to N2 and H2 permeances increasing with temperatures beyond 353K (αNH3/N2 = 46 and αNH3/H2 = 15) and is therefore the optimum temperature for separation. A potential barrier model is developed to describe the hindering effect of NH3 on H2 and N2 permeance. The model fails to predict correctly H2 and N2 permeances in the ternary mixture using pure gas (H2 and N2) permeances. Binary mixture permeation H2/N2 studies showed that there are diffusion effects (single file diffusion) that have not been taken into account in the potential barrier model. When permeances of the individual components in the binary mixture are used in the model instead of the pure gas permeances, there is an improved agreement between experimental and predicted results.
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Shahidi, Kazem. "Composite membranes for gas separation." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/32485.
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Dans ce travail, une méthode efficace est présentée pour la production de membranes composites planes à haute performance pour la séparation de gaz en utilisant une quantité limitée de solvant. En particulier, une série de polydiméthylsiloxane/polyéthylène de basse densité (PDMS/LDPE) a été produite en apposant une couche de PDMS active sur un support de LDPE microporeux produit par extrusion continue et lixiviation de sel et immersion dans l'eau chaude. La méthode proposée est simple et de faible coût car elle est basée sur des matériaux peu dispendieux (LDPE et PDMS) et utilise peu de solvant écologique (eau). En vue d'améliorer la performance et les propriétés des membranes composites, des particules de silice fumée traitée avec le triméthylsiloxy (TFS) ont été incorporées dans la couche de PDMS pour produire des membranes nano-composites PDMS-TFS/LDPE. Les membranes ont ensuite été caractérisées en termes de morphologie, de porosité et de distribution de tailles de pores, ainsi que les propriétés thermiques, mécaniques, de sorption et de perméation. Comme les caractéristiques de la membrane dépendent des conditions de mise en oeuvre, la production des membranes composites a été optimisée en fonction de différents revêtements, de la concentration en nanoparticules et de la concentration de la couche de revêtement. Les performances membranaires (perméabilité et sélectivité) ont été étudiées pour différentes conditions opératoires (température et pression) et les résultats ont montré que la membrane nano-composite PDMS-TFS10%/LDPE est appropriée pour différentes applications industrielles dans la séparation d'hydrocarbures supérieurs.In this work, an efficient method with a limited amount of solvent use is presented to produce high-performance flat sheet composite membranes for gas separation. In particular, a series of polydimethylsiloxane/low-density polyethylene (PDMS/LDPE) membranes were produced by coating an active PDMS layer on a microporous LDPE support via continuous extrusion and salt leaching using immersion in hot water. The proposed method is simple and cost-effective since it is based on inexpensive materials (LDPE and PDMS) and uses a low amount of an environmentally friendly solvent (water). To improve the composite membranes performance and properties, trimethylsiloxy grafted fumed silica (TFS) particles were incorporated into the PDMS layer to produce PDMS-TFS/LDPE nano-composite membranes. The membranes were then characterized in terms of morphology, porosity and pore size distribution, as well as thermal, mechanical, sorption and permeation properties. Since the membrane properties depend on the processing conditions, the composite membranes production was optimized for a different number of coatings, nano-particles loading and coating concentration. Membrane performance (permeability and selectivity) was studied under different operating conditions (temperature and pressure), and the results showed that the PDMSTFS10%/ LDPE nano-composite membrane is highly suitable for different industrial applications of higher hydrocarbon separations.
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Bozorg, Marjan. "Optimization of membrane process architecture." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0252.
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Les procédés de séparation membranaire sont une technologie bien connue et déjà largement utilisée dans le domaine de la purification des gaz. Ces procédés sont applicables à de nombreux secteurs d’activités industriels. Selon les performances de séparation recherchées, elles peuvent constituer une alternative intéressante aux technologies existantes de traitement des gaz (adsorption, cryogénie, contacteurs gaz/liquide). Pour exploiter au mieux cette technologie, le développement d'outils d’aide à la décision permettant d’identifier les procédés et les conditions opératoires économiquement avantageux est absolument nécessaire. Bien que les approches expérimentales d'optimisation appliquées à différentes études de cas conservent un intérêt certain, une approche générale et sa validation dans le cadre de différentes études de cas font toujours défaut. L’objectif principal de cette thèse est de développer un outil numérique le plus générique possible d’optimisation de procédés de séparation membranaire. Dans ce travail, la synthèse du procédé membranaire est traitée et modélisée comme un problème d'optimisation mathématique non linéaire et non convexe basé sur un paradigme de superstructure couvrant une combinatoire d'unités (modules membranaires, compresseurs, pompes à vide) et de connexions la plus exhaustive possible. Des fonctions de coûts réalistes et détaillées sont utilisées comme fonction objectif dans l'optimisation. Une stratégie d'optimisation globale continue, qui peut se considérer comme la composition de deux algorithmes : Multistart et Monotonic Basin Hopping (MBH) ; est présentée pour résoudre le problème d'optimisation susmentionné. L'efficacité de cette démarche d'optimisation est dans un premier temps validée en comparant sa solution à celles présentées dans la littérature. La méthode proposée est ensuite appliquée à l'optimisation de plusieurs cas emblématiques de la séparation de gaz (CO2 de gaz de haut fourneaux, séparation O2/N2 de l’air, traitement du biogaz et du gaz naturel). Différents degrés de liberté du système sont permis et analysés selon les cas (pressions variables, type de membrane variable). L'analyse détaillée des résultats est discutée en termes d’architecture de procédés et de distribution des coûts (CAPEX, OPEX)Membrane separation is a well-known technology in gas purification, which is applicable in different aspects of the industry. Over the last decades, depending on the required separation performances, it became a viable alternative to several gas separation technologies (adsorption, cryogenics, gas /liquid contactors). To exploit at best this technology, nevertheless, tools to find cost-effective designs and operating conditions are necessary. While experimental optimization approaches applied to different case studies have been investigated extensively, a more generic optimization approach and its validation along different case studies are still missing. The work of this thesis starts with this key observation and tries to fill this gap. The membrane process synthesis is modelled as a nonlinear and non-convex mathematical optimization problem based on a superstructure paradigm covering a wide range of possible units (membrane modules, compressors, and vacuum pumps) and connections as exhaustive as possible. Realistic and detailed cost functions are used as the objective in the optimization. A continues global optimization strategy, that can be considered as the composition of two algorithms: Multistart and Monotonic Basin Hopping (MBH); is presented to solve the aforementioned optimization problem. The efficiency of this overall optimization approach is, first, validated by comparing its solution with the ones presented in the literature. Then, the proposed method is applied to the optimization of several important gas separation cases (CO2 recovery from blast furnace gas, O2/N2 air separation, and biogas and natural gas purification) by increasing the membrane system degree of freedom step by step. Detailed analysis of the results is discussed in terms of process architecture and cost distribution (CAPEX, OPEX)
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Nasiri, Syah Johan Ali. "Gas permeabilities and separation in membranes." Thesis, University of Salford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238802.
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Iarikov, Dmitri D. "Novel inorganic membranes for gas separation." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31238.
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A literature survey was performed to evaluate the state-of-the-art membrane systems for CO2/CH4 separation which is critical in the natural gas industry. The systems that were reviewed included zeolite, carbon, polymeric, mixed matrix, amorphous silica, and supported ionic liquid membranes. Supported ionic liquid CO2/CH4 selective membranes were synthesized in our laboratory by applying room temperature ionic liquids (RTILs) to porous inorganic α-alumina supports. The supported ionic liquid membranes (SILMs) displayed CO2 permeance of 1x10-9 to 3x10-8 mol m-2 s-1 Pa-1 and CO2/CH4 selectivity of up to 50 which is comparable with the current polymeric separation systems. It is concluded that, although the RTIL membranes showed good CO2/CH4 selectivity, the CO2 permeance was too low for industrial applications. A new type of SILM was prepared by dissolving 1-aminopyridinium iodide which contained amine functionality in other ionic liquids which improved the CO2 permeance and selectivity of these membranes.
The H2 gas separation is an important process because it has many industrial applications in petroleum processing and chemical synthesis. Amorphous silica membranes for H2 separation were prepared on hollow fiber (HF) inorganic supports using chemical vapor deposition (CVD) of tetraethyl orthosilicate (TEOS). These membranes exhibited good H2 permeance on the order of 10-7 mol m-2 s-1 Pa-1 together with H2/CO2 selectivity of over 100. The separation was achieved using a new hybrid intermediate layer that was developed by depositing a mesoporous silica layer on top of γ-alumina.
Master of Science
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Sarofeim, Marie Thérèse. "Plasma polymerized membranes for gas separation." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/9649.
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A plasma-polymerized thin layer was deposited on the top surface of the skin layer of the asymmetric polyethersulfone Victrex (PES) membrane to plug the ultrafine pores. Aniline was used as the monomer gas of plasma polymerization. Surface characterization by X-ray photoelectron spectroscopy (XPS) measurements has been used to gain insights into the chemistry of plasma-modified membrane surfaces. The steady-state permeation rates for hydrogen, helium, methane, nitrogen, oxygen and carbon dioxide through the asymmetric PES membranes with the plasma modification were measured to evaluate the permeability and the permselectivity. The effect of polyaniline plasma and deposition time on the transport properties of plasma deposits are also discussed. In another set of experiments mixtures of CH$\sb4$/CO$\sb2$ with known compositions were separated using a laminated PES membrane. The modified resistance model was employed to analyze the data of PES membranes laminated with a layer of 1.5 mil silicone unbacked rubber.
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Stevens, Nancy Shanan Moore. "Composite membranes for high temperature gas separations." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/10082.
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Briceño, Mejías Kelly Cristina. "Carbon molecular sieve membranes for gas separation." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/145378.
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Membrane separations are simple, energy efficient processes, which can be economically competitive with traditional separation technologies. In the case of gas separation both dense and porous materials have been developed for different application where hydrogen production is one of the most important niches of development. Hydrogen is being one of the most important vectors to develop alternative clean power generation sources. Nowadays, a lot of processes require the fabrication of pure hydrogen for efficiency and better performance. Different materials have been reported as gas separation membranes but still numerous problems related to stability, cost and fabrication must be overcome. The actual goal is to achieve materials that report good separation properties in new type of configuration facing industrial applications.
Carbon molecular sieve membranes (CMSM) achieve high separation factors and permeance values than polymeric membranes. During the last 30 years they have gained importance due to their excellent performance as gas separation membranes. However, most research work has been focused on flat or hollow fiber configurations and minor attention has been done to supported CMSM. The main reason is due the difficulties associated to fabricate a defect free membrane using a highly reproducible fabrication method that allow to obtain a carbon layer after one polymer precursor coating step. In tubular configuration, these hybrid membranes are suitable for scaling up towards industrial applications, being more competitive than commercial unsupported hollow fiber membranes and films, especially under high pressure and temperature.
The main objective of this work was to explore alternative fabrication methods for the fabrication of supported CMSM. In order to achieve this objective polyimide was coated over inorganic supports using two different approaches. The two methods reported in this thesis were spinning-coating and dip-coating. The idea of spinning¬coating was adapted from fabrication of supported carbon planar film. In this work it was developed the same idea coating TiO2 tubular supports under rotation with polyimide (Matrimid®). The thickness of the carbon membranes was controlled adjusting the viscosity of the polymeric solution, and after an exhaustive solvent
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elimination it was possible to obtain a defect free carbon membrane. The influence of methanol washing, pyrolysis temperature (550-700ºC), and presence of the support allowed to extracting conclusions about the characteristics of the carbon material. Single gas permeance of H2, CO, CO2, N2, CH4 were obtained and ideal selectivity computed from this measurements indicated the presence of pinholes on the carbon membrane. However, the characterization of this carbon obtained after 550º and 700º C by adsorption-desorption analysis allowed to confirm the microporosity of the carbon layer. As an important contribution of this work the influence of the support as pore modifier of the carbon structure is presented after analysis of supported and unsupported samples. Different characterization techniques are presented and integrated in this work to analyze the microporous character of the carbon layer (immersion calorimetry, AFM) and to evaluate the mesoporous characteristics of the asymmetric membrane (liquid-liquid displacement porosimetry). An additional coating procedure with polydimethylsiloxane (PDMS) was performed to decrease the influence of pinholes which caused a permeance decrease but increase on ideal selectivity values over Knudsen theoretical index.
As a second fabrication technique, the modification of Al2O3 inorganic support allowed to achieve microporosity in the support that allowed the fabrication of CMSM by dip¬coating procedure. Similarly to the dip-coating method, viscosity and polymer concentration were optimized in order to achieve high ideal separation factors for hydrogen pairs. For the type of membranes obtained by this method single gas permeance of H2, He, CO2, O2, N2, CH4, Propane, n-butane, 1-butene, SF6 was performed. Influence of pyrolysis temperature, aging, non-solvent immersion, and support were also studied as pore modifier of the carbon membrane. However, for these membranes the characterization was focused on the effect on permeance and selectivity more than in the characterization of the material.
The findings described in this PhD thesis open new perspectives for alternative fabrication techniques of CMSM. This work reports not only the permeance and selective properties of CMSM as the traditional approaches rule. Moreover, brings how each fabrication variable could affect the final properties of the membrane. Integration of structure and properties are presented as an alternative strategy to design new pore architecture on CMSM.
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Hopkins, Janet. "Plasma treatment of polysulfone gas separation membranes." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5231/.
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The chemical and topographical nature of a polymer surface can be changed by non-equilibrium glow discharge treatment. Surface modification of polysulfone and polyethersulfone was examined using a variety of plasma treatments at a fixed power, pressure and treatment time. The modification observed was found to be dependent upon the type of feed gas employed. Tetrafluoromethane plasmas fluorinate polymer surfaces. The influence of polymeric structure on the extent of modification was examined. Phenyl ring containing polymers experienced a greater extent of modification compared to saturated polymers. The extent of modification is dependent upon both the fluorination mechanism and the surface affinity. Plasmas contain a variety of species accompanied by an electromagnetic spectrum. The role of vacuum ultraviolet radiation in a plasma was investigated as a function of feed gas (argon, krypton, xenon and oxygen) on polyethylene and polystyrene, in an oxygen atmosphere. The xenon vacuum ultraviolet treatment gave rise to the greatest oxidation whilst the O(_2) vacuum ultraviolet treatment was found to result in the least oxidation. The activation mechanisms varied with the feed gas chosen for the experiment. Non-equilibrium glow discharge treatment can alter the transport properties of gases permeating through an asymmetric polysulfone membrane. The selectivity and permeability alter as a function of the treatment. The deposition of a methane plasma polymer onto the surface of the membrane resulted in an increase in the gas flux. Similarly CF(_4) plasma treatment also gave rise to an increase in the gas flux. The deposition of a methane plasma polymer followed by a CF(_4) plasma treatment resulted in a decrease in gas flux and a small increase in the oxygen/nitrogen selectivity.
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Deshmukh, Sandeep Prabhakar. "Composite hollow fibre membranes for gas separation." Thesis, University of Leeds, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.423301.
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Zhou, Jian. "Polyacrylonitrile hollow fibre membranes for gas separation." Thesis, University of Leeds, 1996. http://etheses.whiterose.ac.uk/424/.
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Polyacrylonitrile (PAN) hollow fibres have been spun by a dry-jet wet spinning technique, using a commercial PAN polymer (Courtelle) redissolved in dimethylformamide (DMF). After failure to produce satisfactory porous hollow fibres from PAN/DMF solutions, a series of studies on the porous substructure of PAN cast films prepared with a variety of additives in the casting solution and at varying temperatures of the coagulation bath were carried out. A porous and flexible PAN cast film was produced when it was precipitated in water at 55 °C with CuSO4 present in the casting solution. Hollow fibres produced from a spinning solution composed of 25wt% PAN, 70wt% DMF and 5wt% CuSO4 were more porous and flexible than those produced from 25wt% PAN and 75wt% DMF spinning solution, and appeared to be more suitable for gas separation studies. The permeability of the PAN hollow fibre membranes to single gases was studied. The experimental results showed that the calculated pore radius on the surface of the fibre was in the range of 4- 32 nm. After coating with silicone rubber, the membranes showed very poor gas permeability and selectivity. Since PAN has a low intrinsic gas permeability, the low permeability observed is ascribed to a thick skin layer. The low selectivity of the membranes is related to their high surface porosity (> 10-4), or to the large pores present which are imperfectly blocked. With such fibres, little or no gas will pass through the membranes by solution-diffusion in the PAN. In order to reduce the surface porosity on the skin layer of the hollow fibres, a dualbath coagulation spinning system was used. The gas permeability of H2 in these membranes is lower than that obtained by the single bath coagulation system, while the gas permeability of the other gases, such as CO2 and CH4, were too low to measure. These results indicate that a high selectivity can be obtained by the dual bath coagulation spinning system although the selectivity is accompanied by too low a permeability, which is itself caused by too thick a skin layer. Surface modifications of PAN hollow fibre were carried out in order to modify the surface porosity of the fibres. After the treatments, the hollow fibre membranes did not give significant improvement in gas permeability and selectivity. But, when PAN hollow fibres were treated with cuprammonium hydroxide solution at room temperature, the fibres became coloured and no longer soluble in the usual solvents. The insolubility of the fibres is presumed to be due to a newly-formed crosslinked structure. The crosslinking of the fibres is reversed when the fibres are treated with EDTA solution. It has been observed that the presence of the copper in the fibres increases the tensile strength and decreases the elongation of the hollow fibres. The interaction of the PAN fibre with the cuprammonium hydroxide gave no improvement in gas separation performance but might be the basis for general acrylic fibre modification.
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Zou, Yiran. "Gas separation using supported ionic liquid membranes." Thesis, Queen's University Belfast, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517535.
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Lui, Amy M. Y. "Solvent exchange drying of gas separation membranes." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5477.
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Steel, Keisha Marie. "Carbon membranes for challenging gas separations /." Full text (PDF) from UMI/Dissertation Abstracts International, 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3004380.
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Chiu, William. "Processing of Supported Silica Membranes for Gas Separation." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1349815421.
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Escorihuela, Roca Sara. "Novel gas-separation membranes for intensified catalytic reactors." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/121139.
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[ES] La presente tesis doctoral se centra en el desarrollo de nuevas membranas de separación de gases, así como su empleo in-situ en reactores catalíticos de membrana para la intensificación de procesos. Para este propósito, se han sintetizado varios materiales, como polímeros para la fabricación de membranas, catalizadores tanto para la metanación del CO2 como para la reacción de síntesis de Fischer-Tropsch, y diversas partículas inorgánicas nanométricas para su uso en membranas de matriz mixta. En lo referente a la fabricación de las membranas, la tesis aborda principalmente dos tipos: orgánicas e inorgánicas. Con respecto a las membranas orgánicas, se han considerado diferentes materiales poliméricos, tanto para la capa selectiva de la membrana, así como soporte de la misma. Se ha trabajado con poliimidas, puesto que son materiales con temperaturas de transición vítrea muy alta, para su posterior uso en reacciones industriales que tienen lugar entre 250-300 ºC. Para conseguir membranas muy permeables, manteniendo una buena selectividad, es necesario obtener capas selectivas de menos de una micra. Usando como material de soporte otro tipo de polímero, no es necesario estudiar la compatibilidad entre ellos, siendo menos compleja la obtención de capas finas. En cambio, si el soporte es de tipo inorgánico, un exhaustivo estudio de la relación entre la concentración y la viscosidad de la solución polimérica es altamente necesario. Diversas partículas inorgánicas nanométricas se estudiaron para favorecer la permeación de agua a través de los materiales poliméricos. En segundo lugar, en cuanto a membranas inorgánicas, se realizó la funcionalización de una membrana de paladio para favorecer la permeación de hidrógeno y evitar así la contaminación por monóxido de carbono. El motivo por el cual se dopó con otro metal la capa selectiva de la membrana metálica fue para poder emplearla en un reactor de Fischer-Tropsch. Con relación al diseño y fabricación de los reactores, durante esta tesis, se desarrolló el prototipo de un microreactor para la metanación de CO2, donde una membrana polimérica de capa fina selectiva al agua se integró para evitar la desactivación del catalizador, y a su vez desplazar el equilibrio y aumentar la conversión de CO2. Por otro lado, se rediseñó un reactor de Fischer-Tropsch para poder introducir una membrana metálica selectiva a hidrogeno y poder inyectarlo de manera controlada. De esta manera, y siguiendo estudios previos, el objetivo fue mejorar la selectividad a los productos deseados mediante el hidrocraqueo y la hidroisomerización de olefinas y parafinas con la ayuda de la alta presión parcial de hidrógeno.[CAT] La present tesi doctoral es centra en el desenvolupament de noves membranes de separació de gasos, així com el seu ús in-situ en reactors catalítics de membrana per a la intensificació de processos. Per a aquest propòsit, s'han sintetitzat diversos materials, com a polímers per a la fabricació de membranes, catalitzadors tant per a la metanació del CO2 com per a la reacció de síntesi de Fischer-Tropsch, i diverses partícules inorgàniques nanomètriques per al seu ús en membranes de matriu mixta. Referent a la fabricació de les membranes, la tesi aborda principalment dos tipus: orgàniques i inorgàniques. Respecte a les membranes orgàniques, diferents materials polimèrics s'ha considerat com a candidats prometedors, tant per a la capa selectiva de la membrana, així com com a suport d'aquesta. S'ha treballat amb poliimides, ja que són materials amb temperatures de transició vítria molt alta, per al seu posterior ús en reaccions industrials que tenen lloc entre 250-300 °C. Per a aconseguir membranes molt permeables, mantenint una bona selectivitat, és necessari obtindre capes selectives de menys d'una micra. Emprant com a material de suport altre tipus de polímer, no és necessari estudiar la compatibilitat entre ells, sent menys complexa l'obtenció de capes fines. En canvi, si el suport és de tipus inorgànic, un exhaustiu estudi de la relació entre la concentració i la viscositat de la solució polimèrica és altament necessari. Diverses partícules inorgàniques nanomètriques es van estudiar per a afavorir la permeació d'aigua a través dels materials polimèrics. En segon lloc, quant a membranes inorgàniques, es va realitzar la funcionalització d'una membrana de pal¿ladi per a afavorir la permeació d'hidrogen i evitar la contaminació per monòxid de carboni. El motiu pel qual es va dopar amb un altre metall la capa selectiva de la membrana metàl¿lica va ser per a poder emprar-la en un reactor de Fischer-Tropsch. En relació amb el disseny i fabricació dels reactors, durant aquesta tesi, es va desenvolupar el prototip d'un microreactor per a la metanació de CO2, on una membrana polimèrica de capa fina selectiva a l'aigua es va integrar per a així evitar la desactivació del catalitzador i al seu torn desplaçar l'equilibri i augmentar la conversió de CO2. D'altra banda, un reactor de Fischer-Tropsch va ser redissenyat per a poder introduir una membrana metàl¿lica selectiva a l'hidrogen i poder injectar-lo de manera controlada. D'aquesta manera, i seguint estudis previs, el objectiu va ser millorar la selectivitat als productes desitjats mitjançant el hidrocraqueix i la hidroisomerització d'olefines i parafines amb l'ajuda de l'alta pressió parcial d'hidrogen.
[EN] The present thesis is focused on the development of new gas-separation membranes, as well as their in-situ integration on catalytic membrane reactors for process intensification. For this purpose, several materials have been synthesized such as polymers for membrane manufacture, catalysts for CO2 methanation and Fischer-Tropsch synthesis reaction, and inorganic materials in form of nanometer-sized particles for their use in mixed matrix membranes. Regarding membranes manufacture, this thesis deals mainly with two types: organic and inorganic. With regards to the organic membranes, different polymeric materials have been considered as promising candidates, both for the selective layer of the membrane, as well as a support thereof. Polyimides have been selected since they are materials with very high glass transition temperatures, in order to be used in industrial reactions which take place at temperatures around 250-300 ºC. To obtain highly permeable membranes, while maintaining a good selectivity, it is necessary to develop selective layers of less than one micron. Using another type of polymer as support material, it is not necessary to study the compatibility between membrane and support. On the other hand, if the support is inorganic, an exhaustive study of the relation between the concentration and the viscosity of the polymer solution is highly necessary. In addition, various inorganic particles were studied to favor the permeation of water through polymeric materials. Secondly, as regards to inorganic membranes, the functionalization of a palladium membrane to favor the permeation of hydrogen and avoid carbon monoxide contamination was carried out. The membrane selective layer was doped with another metal in order to be used in a Fischer-Tropsch reactor. Regarding the design and manufacture of the reactors used during this thesis, a prototype of a microreactor for CO2 methanation was carried out, where a thin-film polymer membrane selective to water was integrated to avoid the deactivation of the catalyst and to displace the equilibrium and increase the CO2 conversion. On the other hand, a Fischer-Tropsch reactor was redesigned to introduce a hydrogen-selective metal membrane and to be able to inject it in a controlled manner. In this way, and following previous studies, the aim is to enhance the selectivity to the target products by hydrocracking and hydroisomerization the olefins and paraffins assisted by the presence of an elevated partial pressure of hydrogen.
I would like to acknowledge the Spanish Government, for funding my research with the Severo Ochoa scholarship.
Escorihuela Roca, S. (2019). Novel gas-separation membranes for intensified catalytic reactors [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/121139
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Sadeghi, Forouzan. "Development of nanocomposite materials for gas separation membranes." Thesis, University of Ottawa (Canada), 2007. http://hdl.handle.net/10393/27553.
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The objective of this study is to improve the compatibility of nanoparticles in composite materials. This was achieved by developing a method in which an inorganic precursor contained in a stable water/oil (W/O) emulsion was mixed with a polymer solution containing a second inorganic precursor. Inorganic polymerization occurred in the aqueous domain of the W/O emulsion. The in-situ synthesis of the precursor was performed in order to enhance the nanoscale compatibility between the inorganic material and polymer. This technique produced materials which we have named: emulsion polymerized mixed matrix (EPMM) materials.
A series of poly (2,6-dimethyl-1,4-phenylene oxide) (PPO)-based organic-inorganic membranes were prepared by employing this method. A W/O emulsion containing aluminium hydroxonitrate was added to a PPO solution containing tetraethyl orthosilicate (TEOS). Droplet sizes in the W/O emulsions, observed by dynamic light scattering (DLS) ranged from 254 to 344 nm.
Scanning electron micrography (SEM), electron diffractive X-Ray (EDX), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and gas permeation and separation measurements were carried out to characterize the EPMM membranes. SEM indicated the presence of inorganic particles in the PPO matrix, and EDX measurements showed the embedded particles contained Al and Si elements, which confirmed the hydrolysis and condensation of TEOS with aluminium hydroxonitrate. DSC analysis showed a decrease in the glass transition of the EPMM membranes with increasing of TEOS loading. The fractional free volume of the EPMM membranes was predicted through the measurement of the heat capacity jump at the glass transition temperature. The integrity of the EPMM membranes was confirmed in gas separation test with air, in which the ideal selectivity for O2/N2 was observed to be as high as 4.56.
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Mokrani, Touhami. "Transport of gases across membranes." Thesis, Peninsula Technikon, 2000. http://hdl.handle.net/20.500.11838/878.
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Thesis (MTech (Chemical Engineering))--Peninsula Technikon, 2000.Oxygen transport across biofilms and membranes may be a limiting factor in the operation of a membrane bio-reactor. A Gradostat fungal membrane bio-reactor is one in which fungi are immobilized within the wall of a porous polysulphone capillary membrane. In this study the mass transfer rates of gases (oxygen and carbon dioxide) were investigated in a bare membrane (without a biofilm being present). The work provides a basis for further transport study in membranes where biomass is present. The diaphragm-cell method can be employed to study mass transfer of gases in flat-sheet membranes. The diaphragm-cell method employs two well-stirred compartments separated by the desired membrane to be tested. The membrane is maintained horizontally. -The gas (solute) concentration in the lower compartment is measured versus time, while the concentration in the upper liquid-containing compartment is maintained at a value near zero by a chemical reaction. The resistances-in-series model can be used to explain the transfer rate in the system. The two compartments are well stirred; this agitation reduces the resistances in the liquid boundary layers. Therefore it can be assumed that in this work the resistance in the membrane will be dominating. The method was evaluated using oxygen as a test. The following factors were found to influence mass transfer coefficient: i) the agitation in the two compartments; ii) the concentration of the reactive solution and iii) the thickness of the membrane.
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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.
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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.
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Sterescu, Dana Manuela. "Fullerene and dendrimer based nano-composite gas separation membranes." Enschede : University of Twente [Host], 2007. http://doc.utwente.nl/57927.
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