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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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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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Zhou, Yi. "Membrane-Based Gas Separation For Carbon Capture." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595254659184073.
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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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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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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.
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Kratochvil, Adam Michal. "Thickness dependent physical aging and supercritical carbon dioxide conditioning effects on crosslinkable polyimide membranes for natural gas purification." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29678.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Koros, William; Committee Member: Beckham, Haskell; Committee Member: Eckert, Charles; Committee Member: Henderson, Cliff; Committee Member: Meredith, Carson. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Kemmerlin, Ruben Kyle. "Carbon molecular sieve membranes for aggressive sour gas separations." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50135.
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It had been shown that the transport properties of CMS membranes varies as a function of H₂S exposure making the conditioning protocol an important step in identifying the steady state properties of CMS membranes. In this study the conditioning of CMS membranes with H₂S was studied for the determination of the acid gas steady state transport properties. The conditioned steady state has been shown to be the same state for both an extended conditioning protocol using high pressure mixed gas and a rapid conditioning protocol using pure H₂S. The rate of conditioning does vary between the two conditioning protocols as the rapid conditioning protocol takes 48 hours less to reach the conditioned steady state. The results of this study also show that oxygen doping during the formation of the CMS membrane affects the final, conditioned steady state transport properties.
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Kiyono, Mayumi. "Carbon molecular sieve membranes for natural gas separations." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42798.
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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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Lin, Han. "GRAPHENE OXIDE-BASED MEMBRANE FOR LIQUID AND GAS SEPARATION." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron1595260029225206.
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El-Amari, Abdulla Ali. "Separation of acidic gases using hollow fibre membrane contractors." Thesis, University of Salford, 2002. http://usir.salford.ac.uk/26653/.
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Gas absorption in hollow fibre contactors is being increasingly used due to their enormous surface area/volume ratio. The capability of the hollow fibre membrane modules for the removal of CO 2 and SO2 from a binary gas mixture has been investigated experimentally. Four different modules were used in this study. The membranes in modules one and two were made of microporous polypropylene. The third module was made of non-porous silicone rubber (polydimethylsiloxane) while the latter one was a polyvinylidenefluoride (PVDF) asymmetric hollow fibre membrane. The gas mixtures used in the experiments were composed of 9.5% CO2 and 1% SO2 in N 2 , which was introduced into the hollow fibre lumen, while the absorbent liquid was fed into the shell side of module. The absorbent liquids used were water, aqueous solutions of diethanolamine (DBA) and ammonia at different concentrations (5, 10 and 20 wt%). The effects of different operating conditions on the permeation process have been investigated for co-current and counter-current flow patterns. In addition, to improve the silicone rubber hollow fibre membrane performance, baffles were installed within the shell of the permeator to increase liquid fibre contact. The results obtained showed that the use of baffles within the shell of the permeator improved the separation performance of the non-porous membrane module without any substantial increase in the physical size of the contacting device. Studies also showed that improved performance was observed when the system was operated under a counter-current flow pattern. The results showed that the use of an absorbent liquid in the permeate side of the fibres increased the selectivity of the membranes used, and reduced the need to maintain a high pressure ratio across the membrane. A decrease in the feed gas flow rate or increase in liquid flow rate generally improved the removal of gases. The results showed that the use of aqueous reactive solutions as an absorbing medium in the permeate side of the hollow fibre permeator can significantly improve CO2 removal from the gas mixture. However, the main problem when using a microporous membrane coupled with aqueous solutions of diethanolamine as absorbent was wetting of the microporous membrane by amine solutions. For 862 separation, the highest removal was attained using the microporous membrane coupled with water as absorbent liquid. This demonstrates that a hollow fibre based device can be a very efficient gas liquid contactor. The separation process was simulated with a numerical model based on the effective permeabilities of gases and compared with the experimental results. The model simulations showed good agreement with the experimental observations.
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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.
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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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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.
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Shahid, Salman. "Polymer-Metal Organic Frameworks (MOFs) Mixed Matrix Membranes For Gas Separation Applications." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS141/document.
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Le comportement plastifiant de polymères purs a été bien étudié dans la littérature. Toutefois, il n'y a eu que peu d'études concernant les membranes à matrices mixtes (MMM). Dans le chapitre 2 de cette thèse, le comportement plastifiant de MMM préparés à partir de nanoparticules mésoporeuses Fe(BTC) et du polymère Matrimid® est étudié avec un gaz pur ou en mélange. Les réseaux métaux-organiques (MOF) sous forme particulaires ont présenté une relativement bonne compatibilité avec le polymère. L'incorporation de Fe(BTC) dans du Matrimid® a permis d'augmenter la perméabilité et la sélectivité des membranes. Pour de faibles pressions de 5 bars, les MMM ont une perméabilité au CO2 de 60% plus grande ainsi qu'une sélectivité de 29% plus grande à comparer à la sélectivité idéale de membranes Matrimid®. Il a été observé que la présence de particules Fe(BTC) retardait l'effet plastifiant vers de plus grandes pressions. De plus, cette pression augmente avec le taux de MOF au sein du matériau. Ce retard est attribué à la mobilité réduite des chaînes polymères dans l'entourage des particules Fe(BTC). Egalement, pour des concentrations en MOF plus élevées, les membranes présentent une sélectivité plus ou moins constante sur toute la gamme de pression étudiée. Le chapitre 3 présente ensuite la préparation et le caractère plastifiant des MMMs basées sur trois types de MOFs (MIL-53(Al) (MOF « repirant »), ZIF-8 (MOF « flexible ») and Cu3(BTC)2 (MOF « rigide »)) dispersés dans le Matrimid®. Les performances en gaz pur ou en mélange ont été étudiées en fonction de la quantité de MOF introduite. Parmi les trois systèmes MOF-MMM, les membranes avec le Cu3(BTC)2 ont présenté la plus haute sélectivité alors que les membranes avec du ZIF-8 ont montré une plus grande perméabilité. Ces améliorations sont essentiellement le fait de la structure cristalline du MOF et de son interaction avec les molécules de CO2. Le chapitre 4 décrit la préparation de membranes à base de mélange Matrimid® polyimide (PI)/polysulfone (PSF) contenant des particules de ZIF-8 pour la séparation gazeuse à haute pression. Un mélange optimisé avec un rapport PI/PSF de 3:1 a été utilisé pour une étude sur la stabilité et la performance de ces MMMs incorporant différentes concentration de ZIF-8. PI et PSF étant miscibles, une bonne compatibilité avec les particules de ZIF-8 est observée. Les MMMs PI/PSF-ZIF-8 ont démontré une amélioration significative de la perméabilité en CO2 lors de l'augmentation de la concentration en ZIF-8, ce qui a été attribué à une augmentation modérée de la capacité de sorption et à une diffusion plus rapide au travers des particules de ZIF-8. Lors des mesures en gaz purs, les membranes PI/PSF (3:1) ont présenté une plastification vers 18 bars alors que l'introduction de ZIF-8 repousse cette valeur à 25 bars. En mélange de gaz, les MMMs PI/PSF-ZIF-8 ont abouti à une suppression de la plastification comme l'a confirmé une mesure constante de la perméabilité et de la sélectivité du CH4, et cet effet est plus accentué avec l'augmentation de la concentration en ZIF-8. Les résultats en séparation des gaz avec les MMMs PI/PSF-ZIF-8 montrent une performance supérieure à celle du Matrimid® ce qui laisse augurer un élargissement du spectre d'application de ces membranes, particulièrement pour la séparation du CO2 à haute pression. Dans le chapitre 5, une nouvelle voie de préparation des MMMs via la fusion contrôlée de particules a été introduite. La modification du Matrimid® par du 1-(3-aminopropyl)-imidazole a permis d'améliorer considérablement la compatibilité avec les particules de ZIF-8. Il a ainsi été possible de préparer des MMMs contenant 30% de MOF sans perte de sélectivité. En augmentant la concentration en ZIF-8, les MMMs ont de meilleures performances dans la séparation de mélange CO2/CH4 à comparer au polymère initial. La perméabilité a augmenté de plus de 200% avec une augmentation de 65% de sélectivité pour le mélange CO2/CH4The plasticization behavior of pure polymers is well studied in literature. However, there are only few studies on the plasticization behavior of mixed matrix membranes. In Chapter 2 of this thesis, pure and mixed gas plasticization behavior of MMMs prepared from mesoporous Fe(BTC) nanoparticles and the polymer Matrimid® is investigated. All experiments were carried with solution casted dense membranes. Mesoporous Fe(BTC) MOF particles showed reasonably good compatibility with the polymer. Incorporation of Fe(BTC) in Matrimid® resulted in membranes with increased permeability and selectivity. At low pressures of 5 bar the MMMs showed an increase of 60 % in CO2 permeability and a corresponding increase of 29 % in ideal selectivity over pure Matrimid® membranes. It was observed that the presence of Fe(BTC) particles increases the plasticization pressure of Matrimid® based MMMs. Furthermore, this pressure increases more with increasing MOF loading. This delay in plasticization is attributed to the reduced mobility of the polymer chains in the vicinity of the Fe(BTC) particles. Also, at higher Fe(BTC) loadings, the membranes showed more or less constant selectivity over the whole pressure range investigated. Chapter 3 subsequently presented the preparation and plasticization behavior of MMMs based on three distinctively different MOFs (MIL-53(Al) (breathing MOF), ZIF-8 (flexible MOF) and Cu3(BTC)2 (rigid MOF)) dispersed in Matrimid®. The ideal and mixed gas performance of the prepared MMMs was determined and the effect of MOF structure on the plasticization behavior of MMMs was investigated. Among the three MOF-MMMs, membranes based on Cu3(BTC)2 showed highest selectivity while ZIF-8 based membranes showed highest permeability. The respective increase in performance of the MMMs is very much dependent on the MOF crystal structure and its interactions with CO2 molecules. Chapter 4 described the preparation of Matrimid® polyimide (PI)/polysulfone (PSF)-blend membranes containing ZIF-8 particles for high pressure gas separation. An optimized PI/PSF blend ratio (3:1) was used and performance and stability of PI/PSF mixed matrix membranes filled with different concentrations of ZIF-8 were investigated. PI and PSF were miscible and provided good compatibility with the ZIF-8 particles, even at high loadings. The PI/PSF-ZIF-8 MMMs showed significant enhancement in CO2 permeability with increased ZIF-8 loading, which was attributed to a moderate increase in sorption capacity and faster diffusion through the ZIF-8 particles. In pure gas measurements, pure PI/PSF blend (3:1) membranes showed a plasticization pressure of ~18 bar while the ZIF-8 MMMs showed a higher plasticization pressures of ~25 bar. Mixed gas measurements of PI/PSF-ZIF-8 MMMs showed suppression of plasticization as confirmed by a constant mixed gas CH4 permeability and a nearly constant selectivity with pressure but the effect was stronger at high ZIF-8 loadings. Gas separation results of the prepared PI/PSF-ZIF-8 MMMs show an increased commercial viability of Matrimid® based membranes and broadened their applicability, especially for high-pressure CO2 gas separations. In Chapter 5, a novel route for the preparation of mixed matrix membranes via a particle fusion approach was introduced. Surface modification of the polymer with 1-(3-aminopropyl)-imidazole led to an excellent ZIF-8-Matrimid® interfacial compatibility. It was possible to successfully prepare MMMs with MOF loadings as high as 30 wt.% without any non-selective defects. Upon increasing the ZIF-8 loading, MMMs showed significantly better performance in the separation of CO2/CH4 mixtures as compared to the native polymer. The CO2 permeability increased up to 200 % combined with a 65 % increase in CO2/CH4 selectivity, compared to the native Matrimid®. Chapter 6 finally discussed the conclusions and directions for future research based on the findings presented in this thesis
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Adams, Ryan Thomas. "High molecular sieve loading mixed matrix membranes for gas separations." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39470.
Full textAbstract:
Traditional gas separation technologies are thermally-driven and can have adverse environmental and economic impacts. Gas separation membrane processes are not thermally-driven and have low capital and operational costs which make them attractive alternatives to traditional technologies. Polymers are easily processed into large, defect-free membrane modules which have made polymeric membranes the industrial standard; however, polymers show separation efficiency-productivity trade-offs and are often not thermally or chemically robust. Molecular sieves, such as zeolites, have gas separation properties that exceed polymeric materials and are more thermally and chemically robust. Unfortunately, formation of large, defect-free molecular sieve membranes is not economically feasible. Mixed matrix membranes (MMMs) combine the ease of processing polymeric materials with the superior transport properties of molecular sieves by dispersing molecular sieve particles in polymer matrices to enhance the performance of the polymers.
MMMs with high molecular sieve loadings were made using polyvinyl acetate (PVAc) and various molecular sieves. Successful formation of these MMMs required substantial modifications to low loading MMM formation techniques. The gas separation properties of these MMMs show significant improvements over PVAc properties, especially for high pressure mixed carbon dioxide-methane feeds that are of great industrial relevance.
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Ward, Jason Keith. "Crosslinkable mixed matrix membranes for the purification of natural gas." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/39465.
Full textAbstract:
Mixed matrix nanocomposite membranes composed of a crosslinkable polyimide matrix and high-silica molecular sieve particles were developed for purifying natural gas. It was shown that ideal mixed matrix effects were not possible without sieve surface modification. A previously developed Grignard procedure was utilized to deposit magnesium hydroxide nanostructures on the sieve surface in order to enhance polymer adhesion. Analyses of Grignard-treated sieves pointed to the formation of non-selective voids within the surface deposited layer. These voids were suspected to lead to lower-than-expected membrane performance. In order to improve membrane transport, a reactive sizing procedure was developed to fill these voids with polyimide-miscible material. In a serendipitous discovery, as-received sieves--when treated with this reactive sizing procedure--resulted in nearly identical membrane performance as reactive-sized, Grignard-treated sieves. This observation lead to the speculation of a non-ideal transport mechanism in mixed matrix membranes.
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Kim, Danny Jinsoo. "Effects of polymerization conditions and imidization methods on performance of crosslinkable polymer membrane for CO₂/CH₄ separation." Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/48938.
Full textAbstract:
Natural gas feeds often contain contaminants such as CO₂, H₂S, H₂O, and small hydrocarbons. Carbon dioxide is a major contaminant reducing the heating value of the gas and causing pipeline corrosion, so CO₂ level should be lowered to
below 2% to meet the United States pipeline specifications. Membrane separation technology can be advantageous over cryogenic distillation and amine adsorption in terms of cost and efficiency. The key hurdle to overcome in polymeric membrane separation technology is improvement in selectivity, productivity, and durability without introducing significant additional cost. The ultimate goal of this study is to analyze effects due to polymerization
conditions and imidization methods on properties of 1,3-propanediol monoesterified crosslinkable polyimide (PDMC). Hillock, Omole, Ward, and Ma did work on PDMC synthesis; however, variability of polymer properties remains a challenge that must be overcome for industrial implementation of PDMC material. First, reaction temperature and reaction time of polymerization prior to
imidization were considered as key conditions to affect molecular weight, crosslinkability and transport properties of polymer. Batches with controlled reaction
temperature and time were prepared, and properties of each dense film were measured and optimized in terms of permeability, selectivity, and plasticization suppression. Second, imidization methods for PDMC were also studied. There are mainly two kinds of Imidization: chemical Imidization and thermal Imidization. Surprisingly,
thermally imidized PDMC showed 70% higher permeability than chemically imidized samples with minimal acrifice in selectivity. At high reaction temperature during the thermal imidization, transamidation can occur. It is believed that the transamidation
led to more randomized sequence distribution in the thermally imidized samples. We thus hypothesize that the higher permeability of the thermally imidized PDMC results
from greater uniformity of the sequence distribution, as compared to the chemically
imidized sample that does not experience high temperature during imidization. XRD, DSC, DMA, and permeation instruments checked and supported this hypothesis. FTIR, TGA, and NMR ruled out the possibility of an alternate hypothesis related to side reaction. Finally, effects of aggressive feed conditions on both chemically imidized
PDMC and thermally imidized PDMC dense film were examined. The aggressive feed conditions include high CO₂ partial pressure, operating temperatures, and exposure to high feed pressure. Testing aggressive feed conditions for dense film should be pursued before pursuing hollow fiber applications, to decouple effects on the basic material from those on the more complex asymmetric morphology. This study enables understanding of the disparity between various previous
researchers’ selectivity and permeability values. The work shows clearly that polymerization conditions and imidization methods must be specified and controlled to achieve consistently desirable polymer properties. In addition, for batch scale-up and development to a hollow fiber, this fundamental study should enable production of high molecular weight PDMC with good fiber spinnability and defect-free structure.
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Lee, Michael James. "Novel microporous polymers for use as gas separation membranes." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25786.
Full textAbstract:
Polymers of Intrinsic Microporosity (PIMs) combine the desirable processability of polymers with a significant degree of microporosity generated from the inefficient packing of their rigid and contorted structures. They are attracting attention for a variety of applications including as membrane materials for gas separations. Over the last 30 years, membranes have become an established technology for separating gases and are likely to play key role in reducing the environmental impact and costs of many industrial processes such as O2 or N2 enrichment from air, natural gas upgrading and hydrogen recovery from ammonia production. This thesis describes the synthesis of a series of novel PIMs, primarily PIM-polyimide structures (PIM-PI) and investigates their potential in such applications. In particular, it focuses on the design and synthesis of solution processable PIMs in order to study how structural differences affect the gas permeability. The first section describes the synthesis of a variety of PIM-PIs using large bulky diamines derived from spirobisindane (SBI) and biphenylfluorene (BPF) structures which are useful monomers for achieving high BET (Brunauer-Emmett- Teller) surface areas (> 650 m2 g-1). The second section describes a whole series PIs based on novel and literature based Tröger’s base (TB) diamine monomers. Most of these exhibited good solubility, excellent thermal stability and intrinsic microporosity, with apparent BET surface areas in the range 450-739 m2 g-1. Notably, a polyimide derived from Me2TB and pyromellitic anhydride demonstrates gas permeability data above the 2008 upper bounds for important gas pairs such as O2/N2, H2/N2 and H2/CH4. The third section aims to enforce rigidity within the polymers further by incorporating differently substituted monomers based on rigid ethanoanthracene (EA) units. This includes the formation of a novel EA-EA based PI with an exceptionally rigid polymeric structure, possessing a BET surface area of 694 m2 g-1. In addition to very high permeability, this polymer demonstrates improved gas selectivity due to its enhanced performance as a molecular sieve, placing it amongst some of the highest performing polymers to date. The final section looks at other ways in which rigidity can be enforced including the formation of TB-polymers and thermally rearranged (TR) polymers and assesses their potential for future investigations.
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Harlacher, Thomas [Verfasser]. "Membrane separation processes for Argon plasma gas recovery / Thomas Harlacher." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1049352165/34.
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Xu, Liren. "Carbon molecular sieve hollow fiber membranes for olefin/paraffin separations." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50130.
Full textAbstract:
Olefin/paraffin separation is a large potential market for membrane applications. Carbon molecular sieve membranes (CMS) are promising for this application due to the intrinsically high separation performance and the viability for practical scale-up. Intrinsically high separation performance of CMS membranes for olefin/paraffin separations was demonstrated. The translation of intrinsic CMS transport properties into the hollow fiber configuration is considered in detail. Substructure collapse of asymmetric hollow fibers was found during Matrimidﾮ CMS hollow fiber formation. To overcome the permeance loss due to the increased separation layer thickness, 6FDA-DAM and 6FDA/BPDA-DAM polyimides with higher rigidity were employed as alternative precursors, and significant improvement has been achieved. Besides the macroscopic morphology control of asymmetric hollow fibers, the micro-structure was tuned by optimizing pyrolysis temperature protocol and pyrolysis atmosphere. In addition, unexpected physical aging was observed in CMS membranes, which is analogous to the aging phenomenon in glassy polymers. For performance evaluation, multiple "proof-of-concept" tests validated the viability of CMS membranes under realistic conditions. The scope of this work was expanded from binary ethylene/ethane and propylene/propane separations for the debottlenecking purpose to mixed carbon number hydrocarbon processing. CMS membranes were found to be olefins-selective over corresponding paraffins; moreover, CMS membranes are able to effectively fractionate the complex cracked gas stream in a preferable way. Reconfiguration of the hydrocarbon processing in ethylene plants is possible based on the unique CMS membranes.
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Nakaye, Shoeji. "Studies on a thermal method of gas separation with porous membrane." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215512.
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Cooper, Charlie Austin. "CVD Modification and Vapor/Gas Separation Properties of Alumina Membranes." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1004998070.
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Liu, Ran. "Synthesis and Characterization of Novel Polybenzimidazoles and Post-modifications for Membrane Separation Applications." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/96200.
Full textAbstract:
Polybenzimidazoles, a class of aromatic heterocyclic polymers, are well known due to their remarkable thermal stability, mechanical properties and chemical resistance which are often required in extreme operation conditions. Because of these properties, polybenzimidazoles are excellent candidates in various application areas including proton exchange membrane fuel cells, gas separation membranes, reverse osmosis and nanofiltration, and high performance coatings. The following studies are focused on the synthesis, characterization and related properties of polybenzimidazoles and polybenzimidazole based materials.
A novel sulfonyl-containing tetraamino-substituted monomer (3,3',4,4'-tetraaminodiphenylsulfone) was synthesized and polymerized with three different diacid monomers to make polybenzimidazoles. The new monomer synthesis route with reduced steps relative to the existing literature method increased the overall yield by a factor of three. The sulfonyl-containing polybenzimidazoles have enhanced solubilities in common organic solvents including dimthylsulfoxide, dimethylacetamide and N-methyl-2-pyrrolidone in comparison with the commercial polybenzimidazole, Celazole ®, poly(2,2'-(m-phenylene)-5,5'-bibenzimidazole). The improvements in solubility are attributed to the introduction of polar sulfonyl linking moiety in the monomer. Remarkable thermal stabilities (high Tg, > 428 oC) were demonstrated through Dynamic Mechanical Analysis (DMA) and Thermogravimetric Analysis (TGA). A well designed film casting process was investigated and established. Polybenzimidazoles were
fabricated into transparent thin films (20-30 μm thick) for gas transport measurements. These novel polybenzimidazole films exhibited extraordinary gas separation properties, especially for H2/CO2 separation.
There is a trade-off relationship between gas permeability and selectivity through dense, non-porous polymer membranes that was discovered by Robeson in 1991. The ultimate goal for developing gas separation membranes is to improve both permeability and selectivity simultaneously. Gas permeability is related to the free volume between polymer chains. In order to improve gas permeability, we hypothesized a concept that increasing free volume could be achieved by thermally degrading sacrificial components and volatilizing their byproducts from a glassy matrix. Volatile components were introduced into the films to preoccupy the spaces between polymer chains. Once they were degraded and removed through the thermal treatment, it was hypothesized that the preoccupied spaces would remain empty due to the glassy nature of the matrix at the heat treatment temperature, thus resulting in more free volume. Two post- modification strategies including grafting and blending were utilized to incorporate the volatile components, poly(propylene oxide) and poly(ethylene oxide). Post-modified polybenzimidazole films impressively showed significant enhancements in both gas permeability and selectivity for H2/CO2 separation. The H2 permeability of the post-modified TADPS-OBA polybenzimidazole increased from 3.1-6.2 Barrers to 5.2-7.5 Barrers (up to 66% increase). The selectivity for H2/CO2 increased from 7.5-10.5 to 10.1-13.0 (up to 33% increase). The study on the potential effects of water vapor on the separation performance of PBI membranes was discussed in the appendix.Ph. D.
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Achoundong, Carine Saha Kuete. "Engineering economical membrane materials for aggressive sour gas separations." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50289.
Full textAbstract:
The goal is of this project was to identify principles to guide the development of high performance dense film membranes for natural gas sweetening using hydrogen sulfide and carbon dioxide gas mixtures as models under aggressive sour gas feed conditions. To achieve this goal, three objectives were developed to guide this research.
The first objective was to study the performance of cellulose acetate (CA) and an advanced crosslinkable polyimide (PDMC) dense film membrane for H₂S separation from natural gas.
The second objective was to engineer those polymers to produce membrane materials with superior performance as measured by efficiency, productivity, and plasticization resistance, and the third objective was to determine the separation performance of these engineered membrane materials under more aggressive, realistic natural gas feeds, and to perform a detailed transport analysis of the factors that impact their performance.
Work on the first objective showed that in neat CA, penetrant transport is controlled by both the solubility and mobility selectivity, with the former being more dominant, leading to a high overall CO₂/CH₄ (33) and H₂S/CH₄ (35) ideal selectivities. However, in uncrosslinked PDMC, H₂S/CH₄ selectivity favored sorption only, whereas CO₂/CH₄ selectivity favored both mobility and sorption selectivity, leading to a high CO₂/CH₄ (37) but low H₂S/CH₄ (12) ideal selectivities. However, the latter polymer showed more plasticization resistance for CO₂.
In the second objective, both materials were engineered. A new technique referred to as “GCV-Modification” was introduced in which cellulose acetate was grafted using vinyltrimethoxysilane (VTMS), then hydrolyzed and condensed to form a polymer network. PDMC was also covalently crosslinked to enhance its performance. GCV-Modified CA showed significant performance improvements for H₂S and CO₂ removal; the permeability of CO₂ and H₂S were found to be 139 and 165 Barrer, respectively, which represented a 30X and 34X increase compared to the pristine CA polymer. The H₂S/CH₄ and CO₂/CH₄ ideal selectivities were found to be 39 and 33, respectively. Crosslinked PDMC showed a higher CO₂/CH₄ selectivity of 38 with a better plasticization resistance for CO₂ and H₂S.
In the third objective, these materials were tested under aggressive ternary mixtures of H₂S/CO₂/CH₄ with both vacuum and nonvacuum downstream. Even under aggressive feed conditions, GCV-Modified CA showed better performance vs. PDMC, and it remained were fairly stable, making it a potential candidate for aggressive sour gas separations, not only because of its significantly higher productivity, which will help decrease the surface area needed for separation, thereby reducing operating costs, but also because of the lower cost of the raw material GCV-Modified CA compared to PDMC.
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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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Van, Vuuren Marcelle. "Membrane gas separation of Fischer-Tropsch gases / by M. van Vuuren." Thesis, North-West University, 2005. http://hdl.handle.net/10394/1140.
Full textAbstract:
Membrane-based gas separation has attracted considerable interest over the past few years
because of its low energy consumption and cost-effective separation. Many studies have been
conducted related to amorphous silica membrane. This membrane has been reported to
perform well with respect to separating various gases including the Sasol Fischer Tropsch
gases Hydrogen, Methane and Carbon dioxide.
This study is devoted to the investigation of the performance of a commercially available
amorphous silica membrane for the separation of a typical Fischer Tropsch gas mixture.
For both single and binary permeation experiments performed, it was found that the membrane
permeation of the gases Hydrogen, Methane and Carbon dioxide is independent of the transmembrane
pressure.
As far as temperature is concerned, it was established that the permeation of the three gases is
inversely dependent on an increase in operating temperature. This was observed for both
single and binary permeation experiments.
In general, higher fluxes were achieved if the gases were fed directly onto the support (shell
side feed).
Selectivity towards Hydrogen was not significantly influenced by any of the operating
parameters investigated (temperature, trans-membrane pressure, membrane orientation).
The overall conclusions that were made based on the results obtained are that this membrane
can essentially be classified as a Knudsen-type membrane, since selectivity values are in the
region of Knudsen transport. The selectivity values are thus not large enough to qualify this
membrane as a successful gas separation membrane.
It was however, established that this membrane may perform more effectively if used for
pervaporation application purposes.Thesis (M.Ing. (Chemical Engineering))--North-West University, Potchefstroom Campus, 2006.
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Farr, Isaac Vincent. "Synthesis and Characterization of Novel Polyimide Gas Separation Membrane Material Systems." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/28590.
Full textAbstract:
Phenylindane monomers 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (DAPI), 5,6-diamino-1-(4-aminophenyl)-1,3,3-trimethylindane (TAPI) and 6-hydroxy-
1-(4-hydroxyphenyl)-1,3,3-trimethylindane (DHPI) were synthesized and characterized. DAPI, as well as other diamines, were then utilized in solution step polycondensation with a number of commercially available dianhydrides using either the two-step ester-acid solution imidization or the high temperature solution imidization routes. High molecular weight soluble fully cyclized polyimides were successfully synthesized using a 1:1 molar ratio of dianhydride to diamine. The polyimides were film forming and were characterized by size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and selective gas permeation methods, as well as other techniques. The O2 permeation and O2/N2 selectivity values obtained for materials prepared in this thesis are discussed in relation to the concept of an "upper bound", as defined in the literature concerning gas separation membranes.
The series of polyimides based on DAPI and several dianhydrides were found to have high glass transition temperatures (247°C-368°C) and very good short-term thermal stability as shown by TGA, despite the partially aliphatic character of DAPI. The 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzenefurandione (6FDA)/DAPI system also exhibited low weight loss under nitrogen at 400°C, which was comparable to that of a wholly aromatic polyimide based on 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA)/4,4'-oxydianiline (ODA) which is known to have high thermal stability. In addition, the 6FDA/DAPI polyimides had a refractive index value of 1.571 from which the dielectric constant was calculated, giving an attractively low estimated value of 2.47.
The rigid, bulky and isomeric structure of DAPI in the repeat unit imparted film forming characteristics that allowed production of solvent cast membranes which displayed a range of O2 permeability and O2/N2 selectivity characteristics. High O2 permeabilities were observed for polyimides in which the DAPI structure predominated in relation to the overall polymer repeat unit, i.e. in combination with low molar mass dianhydrides. The more flexible dianhydrides afforded a greater degree of molecular freedom and were thought to result in a more tightly packed polymer conformation which decreased the rate of gas penetration through thin films. The DAPI/3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) system showed the best combination of O2 permeability and O2/N2 selectivity values (2.8Ba and 7.3, respectively). Modest variations in the DAPI isomeric ratio did not significantly effect the gas permselectivity properties.
High molecular weight polyimides based on DAPI and BTDA were synthesized by three different routes. The ester-acid and thermal imidization methods produced polyimides with the highest Tgs and best thermal stability in air, as compared to the chemical imidization procedure. For example, a Tg increase of 22°C and a 68°C increase in the 5% weight loss were found for the ester-acid imidized DAPI/BTDA polyimide over those found for the chemically imidized version. The higher Tg and 5% weight loss values were attributed to the elimination of residual uncyclized amide acid moieties.
Polyimides derived from 6FDA were synthesized by the high temperature solution imidization method. Thin films, cast from NMP, were tough and creasable and afforded high Tg (>295°C) systems with good thermal stability. When combined with rigid diamines, 6FDA contributed to high O2 permeation and moderate O2/N2 selectivity. The high O2 permeability was ascribed to hindered interchain packing attributed to the bulky CF3 groups. The exceptionally high oxygen permeability and O2/N2 selectivity values of the 9,9-bis(4-aminophenyl) fluorene (FDA)/6FDA system, were near the desirable "upper bound" for gas separation membrane materials, while those of 3,7-diamino-2,8-dimethyl-dibenzothiophene-5,5-dioxide (DDBT)/6FDA were actually above the upper bound.
High performance polymers based on 4,4'-bis [4-(3,4-dicarboxyphenoxy)]biphenyl dianhydride (BPEDA), 2,2'-bis [4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride (BPADA), 2,2-bis(3-amino-4-methylphenyl)hexafluoroisopropylidene dianhydride (Bis-AT-AF) and 3,7-diamino-2,8-dimethyl-dibenxothiophene-5,5-dioxide (DDBT) were also synthesized in this work. Additionally, they were characterized with regard to molecular weight, glass transition temperature, and thermal stability.
Polyimide systems containing hydroxyl moieties in the repeat unit were also investigated. Incorporation of hydroxyl moieties in the repeat unit enhanced chain stiffness via intermolecular hydrogen bonding and showed Tg increases of ~30°C Hydroxyl moieties also decreased the thermal stability values typically observed for polyimides. High O2/N2 selectivity was achieved with all of the 4,4'-diaminobiphenyl-3,3'-diol (HAB) containing polymers. However, these materials also had low O2 permeabilities, which suggested a tightly packed structure, possibly facilitated by hydrogen bonding. In contrast to suggestions in the literature, the comparison between a polyimide having pendant hydroxyl groups and another having the same repeat unit without them did not reveal a significant change in permselectivity behavior.
The synthesis, characterization and crosslinking behavior of functional polyimides containing phenol, amine and acetylene moieties are also described. A crosslinking reaction of oligomers containing phenol moieties with a tetrafunctional epoxy resin was achieved 100°C below the "dry" glass transition temperature and was attributed to residual solvent. Utilization of this crosslinking mechanism could allow membrane optimization by investigating the influence of a number of variables, such as the concentration of the phenolic moiety, epoxy weight percent, catalyst concentration and residual solvent content.Ph. D.
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Malpass-Evans, Richard. "Microporous polymers containing tertiary amine functionality for gas separation membrane fabrication." Thesis, Cardiff University, 2014. http://orca.cf.ac.uk/65421/.
Full textAbstract:
This research reported in this thesis is based on the synthesis of novel polymers of intrinsic microporosity (PIMs) with the aim of fabricating membranes for gas separation applications. PIMs are composed of rigid and awkwardly-shaped monomeric segments which lack the conformational and rotational freedom needed to pack space efficiently. As a result these polymers display high BET surface areas and display excellent gas permeabilities when solution-cast into films which can be used as gas separation membranes. This thesis describes the synthesis of a range of aromatic diamine, tetraamine, dianhydride, and dicarboxylic acid monomers that conform to the PIM design concept, featuring rigid and contorted architectures. These monomers were then used to synthesise five classes of polymer featuring tertiary amine functionality. Structure-property relationships were established between these polymers and BET surface area measurements. Polymers that displayed adequate film forming properties were also evaluated by our collaborators at The Institute of Membrane Technology for their gas transport parameters. Chapter 6 describes the synthesis of a new class of polymer, Tröger's Base PIMs, featuring a novel polymerisation reaction using chemistry first reported 127 years ago. One of these polymers, DMEA.TB, displays a BET surface area of 1028 m2/g which is the highest recorded for any soluble polymer to date. DMEA.TB places gas permeation data for technologically important gas pairs far over the present Robeson upper bound and has unrivalled potential to separate mixtures containing hydrogen. Chapter 7 deals with quaternerisation and subsequent ion exchange of selected Tröger's Base polymers. Chapter 8 discusses the synthesis of three novel polyimides using highly rigid and contorted ethanoanthracene monomers containing methyl groups that restrict rotation around polymer segments. These polymers display only moderate gas permeation characteristics and possess BET surface areas of up to 694 m2/g. Chapter 9 describes the synthesis of a new class of zwitterionic polysquaraines however, these polymers were shown to be non-porous due to strong ionic/hydrogen bonding. Chapter 10 describes the synthesis of polybenzimidazoles using the PIM design concept but it was found that extensive hydrogen bonding reduces free volume, forming non porous solids. Chapter 11 describes the synthesis of novel polypyrrolones with surface areas of up to 284 m2/g however, film formation was not possible with these materials. Chapter 12 features a brief investigation onto the cross-linking of a Tröger's Base membrane using hydrolysed PIM-1 as polyanionic counterion.
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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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Linck, Nicholas W. "MIXED MATRIX FLAT SHEET AND HOLLOW FIBER MEMBRANES FOR GAS SEPARATION APPLICATIONS." UKnowledge, 2018. https://uknowledge.uky.edu/cme_etds/89.
Full textAbstract:
Mixed matrix membranes (MMM) offer one potential path toward exceeding the Robeson upper bound of selectivity versus permeability for gas separation performance while maintaining the benefits of solution processing. Many inorganic materials, such as zeolites, metal-organic frameworks, or carbon nanotubes, can function as molecular sieves, but as stand-alone membranes are brittle and difficult to manufacture. Incorporating them into a more robust polymeric membrane matrix has the potential to mitigate this issue.
In this work, phase inversion polymer solution processing for the fabrication and testing of asymmetric flat sheet mixed matrix membranes was employed with CVD-derived multiwall carbon nanotubes (MWCNTs) dispersed in a polyethersulfone (PES) matrix. The effect of MWCNT loading on membrane separation performance was examined. Notably, a distinct enhancement in selectivity was measured for several gas pairs (including O2/N2) at relatively low MWCNT loading, with a peak in selectivity observed at 0.1 wt% loading relative to PES. In addition, no post-treatment (e.g. PDMS caulking) was required to achieve selectivity in these membranes. In contrast, neat PES membranes and those containing greater than 0.5 wt.% MWCNT showed gas selectivity characteristic of Knudsen diffusion through pinhole defects. These results suggested that at low loading, the presence of MWCNTs suppressed the formation of surface defects in the selective layer in flat sheet mixed matrix membranes.
Additionally, a bench-scale, single-filament hollow fiber membrane spinning line was designed and purpose-built at the University of Kentucky Center for Applied Energy Research (CAER). Hollow fiber membrane spinning capability was developed using polyethersulfone (PES) solution dopes, and the process was expanded to include polysulfone (PSf) as well as mixed matrix membranes. The effects of key processing parameters, including the ratio of bore to dope velocities, the spinning air gap length, and the draw-down ratio, were systematically investigated. Finally, direct hollow fiber analogues to flat sheet mixed matrix membranes were characterized. Consistent with the flat sheet experiments, the mixed matrix hollow fiber membranes showed a local maximum in selectivity at a nominal loading of 0.1 wt.% MWCNT relative to the polymer, suggesting that the pinhole suppression effect introduced by MWCNTs was not limited to flat sheet membrane casting.
The development of asymmetric hollow fiber mixed matrix membrane processing and testing capability at the UK Center for Applied Energy Research provides a platform for the further development of gas separation membranes. Using the tools developed through this work, it is possible to further push the frontiers of mixed matrix gas separation by expanding the capability to include more polymers, inorganic fillers, and post treatment processes which previously have been focused primarily on the flat sheet membrane geometry.
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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.
Full textAbstract:
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.
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Skischally, Silvia Parisi. "Gas permselectivity in amorphous linear and crosslinked poly(arylene ether ketones)." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41923.
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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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Gilassi, S., and Nejat Rahmanian. "An experimental investigation into the permeability and selectivity of PTFE membrane: a mixture of methane and carbon dioxide." Taylor & Francis, 2016. http://hdl.handle.net/10454/18549.
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noResearch and technology innovations in the 1970s led to the significant commercial practice of gas separation by membranes that exists today. These advances involved developing membrane structures that could produce high fluxes and modules for packing a large amount of membrane area per unit volume (Murphy et al., 2009). At present, the share of using a polymeric membrane in the capture of CO2 is increasing and gradually the membrane technology is considered as the promising method in separation units, although the number of commercial membranes is not high. CO2 capture from natural gas is one of the controversial topics that many researchers and engineers try to find the best method satisfying both high efficiency and low capital cost. In common, chemical physical absorption towers are applied to remove CO2 from natural gas in order to prevent pipeline corrosion, even though the other component such as H2S gives rise to operating problems. The obscure angle of a conventional unit is related to the high energy consumption while the absorbent needs to be purified by the regeneration units which implement the temperature as a unique manipulating parameter for separating amine groups. The great advantages of using the membrane in gas industry are the low capital cost, easy installation and maintenance so that for this simple reason, new membranes come to the market for different types of processes. Capture of CO2 from natural gas accounts for one of the major difficulties so that the engineers try to employ membrane modules as to alter the process efficiency. However, there are only a limited number of membranes that can be used in real industry and the research still continues over this interesting topic (Burggraaf and Cot, 1996).
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Bigliardi, Brando. "Study of PVAm-graphene selective layer on PES membrane for gas separation." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
Many studies focused on the improvement of membrane performance by addition of nanofiller creating the so-called mixed matrix membranes. In this work, the feasibility of producing a multi-layer selective membrane for carbon dioxide separation is analysed. Two different deposition technique, 2-D printing and Mayer bar deposition, were explored. The multi-layer membranes were composed by a support layer of polyethersulfone and a selective layer of polyvinyl amine and graphene.
Some consideration about ink formulation for 2-D printing were also developed in this work.
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Lou, Yuecun. "Transport Modeling and CFD Simulation of Membrane Gas Separation Materials and Modules." University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1407020499.
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Hinchliffe, Anthony Bernard. "The separation of hydrogen and carbon monoxide using polymer membranes." Thesis, Aston University, 1991. http://publications.aston.ac.uk/9756/.
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This work studies the development of polymer membranes for the separation of hydrogen and carbon monoxide from a syngas produced by the partial oxidation of natural gas. The CO product is then used for the large scale manufacture of acetic acid by reaction with methanol. A method of economic evaluation has been developed for the process as a whole and a comparison is made between separation of the H2/CO mixture by a membrane system and the conventional method of cryogenic distillation. Costs are based on bids obtained from suppliers for several different specifications for the purity of the CO fed to the acetic acid reactor. When the purity of the CO is set at that obtained by cryogenic distillation it is shown that the membrane separator offers only a marginal cost advantage. Cost parameters for the membrane separation systems have been defined in terms of effective selectivity and cost permeability. These new parameters, obtained from an analysis of the bids, are then used in a procedure which defines the optimum degree of separation and recovery of carbon monoxide for a minimum cost of manufacture of acetic acid. It is shown that a significant cost reduction is achieved with a membrane separator at the optimum process conditions. A method of "targeting" the properties of new membranes has been developed. This involves defining the properties for new (hypothetical -yet to be developed) membranes such that their use for the hydrogen/carbon monoxide separation will produce a reduced cost of acetic acid manufacture. The use of the targeting method is illustrated in the development of new membranes for the separation of hydrogen and carbon monoxide. The selection of polymeric materials for new membranes is based on molecular design methods which predict the polymer properties from the molecular groups making up the polymer molecule. Two approaches have been used. One method develops the analogy between gas solubility in liquids and that in polymers. The UNIFAC group contribution method is then used to predict gas solubility in liquids. In the second method the polymer Permachor number, developed by Salame, has been correlated with hydrogen and carbon monoxide permeabilities. These correlations are used to predict the permeabilities of gases through polymers. Materials have been tested for hydrogen and carbon monoxide permeabilities and improvements in expected economic performance have been achieved.
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Borjigin, Hailun. "Synthesis and Characterization of High Performance Polymers for Gas Separation Membranes." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/74231.
Full textAbstract:
This dissertation focuses on the synthesis and characterization of high performance polymers, especially polyimides, polybenzoxazoles and polybenzimidazoles for gas separation applications. An abundance of monomers and novel polymers were synthesized and fabricated into membranes.
Thermally rearranged polybenzoxazoles and their precursor polyimides were systematically studied with regard to size of pendant functional groups, thermal rearrangement conversion, and relationship of backbone structure/gas transport properties. 3,3'-Diamino-4,4'-dihydroxybiphenyl was synthesized using an economical route. Meta and para oriented polyimides with different ortho-functionality were synthesized and these polymers were thermally rearranged into polybenzoxazoles. The polar hydroxyl functional groups on the polyimide backbone diminished the meta/para isomer effect of the permeability coefficients of the polymers and only a small difference between meta- and para-oriented polyhydroxyimides in permeability coefficients was observed. The TR polybenzoxazoles derived from meta/para-oriented isomeric polyimides with ortho functionality had similar gas separation properties, especially for CO2/CH4 separation, and it is hypothesized that this is due to a lack of intersegmental mobility distinction between the two isomeric TR polymers. The TR polymers derived from the polyimides with acetate ortho-functional groups had significantly better gas separation properties than ones derived from the precursor with hydroxyl ortho-functional groups.
Polybenzimidazoles were also investigated for use as gas separation membranes. Polybenzimidazoles are some of the most thermally stable polymers. However, commercial polybenzimidazoles do not have good solubility in common solvents. The solubility issue was solved by incorporating sulfonyl linkages into the polybenzimidazole backbone using a 3,3',4,4'-tetraaminodiphenylsulfone (TADPS) monomer. 3,3',4,4'-Tetraaminodiphenylsulfone was synthesized by a novel route with higher overall yield and less steps than the traditional synthetic method. The TADPS based polybenzimidazoles also demonstrated better thermal stability than commercial polybenzimidazole. The meta/para oriented isomer effect on gas transport properties is discussed. TADPS-based polybenzimidazoles exhibited H2/CO2 gas separation properties near or surpassing the upper bound with H2 permeabilities from 3.6 to 5.7 Barrer and selectivities from 10.1 to 32.2 at 35 °C.Ph. D.
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Deyhim, Sina. "Deriving Gas Transport Properties of Microporous Silica Membranes from First Principles and Simulating Separation of Multi-Component Systems in Different Flow Configurations." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31340.
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Amorphous silica membranes have molecular sieving properties for the separation of hydrogen from gas mixtures at high temperature. Consequently, they are considered to be applied in separation of a shifted syngas coming out of a water-gas-shift-reactor into the syngas and hydrogen. This separation is a key to an Integrated Gasification Combined Cycle (IGCC) plant, which would allow reducing the carbon footprint in power generation industry. The main objective of this thesis was to carry out a preliminary assessment of suitability of currently available amorphous silica membranes for this separation. However, the separation properties of amorphous silica membranes reported in the open literature vary by orders of magnitude. Therefore, in the first part of this thesis the separation properties of hypothetical silica membrane with different pore size distributions were predicted from first principles.
Considering different possible gas transport mechanisms, it was concluded that gas transport in amorphous silica membranes is dominated by the activated and non-activated Knudsen diffusion. The activation energy for transport of different species was predicted using the concept of suction energy. Then, with arbitrary pore size distributions gas permeance of hypothetical silica membrane was predicted for different gas species. Since the pore size distribution of amorphous silica membrane cannot be known a priori, the developed model was used to determine the pore size distribution based on experimentally measured single gas permeances of three different species (kindly provided by Natural Resources Canada, CANMET Energy Technology Center (CETC) laboratory in Ottawa) by minimizing the error of the calculated permeance ratios with respect to the experimental values. The results indicate that, depending on how the objective function is defined, more than one pore size distribution can be found to satisfy the experimental permeance ratios. It is speculated that by increasing the number of experimentally determined permeances, a more unique pore size distribution for the tested silica membrane can be obtained. However, even at this early stage, the developed model provides a rational explanation for the effect of membrane densification on the properties of silica membranes. More specifically, a simultaneous decrease in membrane permeance and selectivity due to membrane densification, reported in the literature, is explained by shrinking the size of pores beyond a certain critical value, which depends on the kinetic diameter of gas molecules that are being separated.
Comparing theoretically determined permeances, which match experimentally observed permeance ratios, revealed that the experimental permeances are considerably smaller than the theoretical values. The ratio of the two provided the basis for a scaling factor, a new concept that was introduced in this thesis.
To simulate membrane module performance, a novel approach was introduced. More specifically, co- and counter-current flow configurations as well as cross-flow configuration were modeled by assuming no change in feed composition over an infinitesimally small element of membrane area. This led to a system of linear, rather than differential equations, which was readily solved numerically.
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Ning, Xue. "Carbon molecular sieve membranes for nitrogen/methane separation." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53986.
Full textAbstract:
Nitrogen-selective Carbon Molecular Sieve (CMS) membranes were developed for nitrogen/methane separation. Effects of pyrolysis conditions including pyrolysis temperature protocol and pyrolysis atmosphere were studied for Matrimid® and 6FDA:BPDA-DAM precursors. It was revealed that high pyrolysis temperature is essential to achieve attractive nitrogen/methane selectivity due to the subtle size difference between the two gas penetrants. Detailed study on one of the best performing CMS membranes showed that diffusion selection, more specifically, the entropic factor responsible for diffusion selection provides a significant contribution to the high selectivity. The effect of precursor was studied by considering nine carefully selected polymers. The structures and properties of these polymer precursors were compared and correlated with the separation performance of resulting CMS membranes. The translation of intrinsic CMS transport properties into the hollow fiber morphology was also explored. Substructure collapse and asymmetry lost during pyrolysis were observed, which resulted in significant increases of separation layer thickness and decreases in permeance. Vinyltrimethoxy silane (VTMS)-treatment was applied to polymer hollow fiber before pyrolysis to overcome the problem of substructure collapse. The effects of VTMS-treatment on both the substructure and skin layer are discussed.
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Tang, Zhong. "Synthesis and Modification of MFI-Type Zeolite Membranes for High Temperature Hydrogen Separation and Water Gas Shift Membrane Reactions." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1283192205.
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Keskin, Seda. "Accelerating development of metal organic framework membranes using atomically detailed simulations." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31679.
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Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2010.Committee Chair: Sholl, David S.; Committee Member: Chance, Ronald R.; Committee Member: Jang, Seung Soon; Committee Member: Koros, William J.; Committee Member: Nair, Sankar. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Sen, Deser. "Effect Of Compatibilizers On The Gas Separation Performance Of Polycarbonate Membranes." Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1262963/index.pdf.
Full textAbstract:
In this study, the effect of compatibilizers on the gas separation performance of polycarbonate (PC) membranes was investigated. Membranes were prepared by solvent evaporation method. They were characterized by single gas permeability measurements of O2, N2, H2 and CO2 as well as scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared spectrometry (FTIR).
Membranes containing 0.5 to 10 w% p-nitroaniline (pNA) were prepared to study the effect of compatibilizer concentration on the membrane performance. Permeabilities of all gases decreased but selectivities increased with pNA
concentration. The membranes with 5 w% pNA showed a selectivity of 114.5 for
H2 over N2, 53.9 for CO2 over N2 and 13.4 for O2 over N2 at room temperature, whereas, the H2/N2, CO2/N2 and O2/N2 selectivities for pure PC membranes were 43.5, 20.6 and 5.6, respectively. The N2 permeabilities through pure PC membrane and 5 w% pNA/PC membrane were 0.265 and 0.064 barrer, respectively.
The glass transition temperature of the membranes decreased with increasing pNA concentration. FTIR spectra showed that the peaks assigned to nitro and amine groups of pNA shifted and/or broadened. The DSC and FTIR results suggested an interaction between PC and pNA.
The effect of type of compatibilizer was also studied. The compatibilizers were 4-amino 3-nitro phenol (ANP), Catechol and 2-hydroxy 5-methyl aniline (HMA). Similar to membranes prepared with pNA, membranes prepared with these compatibilizers had a lower permeability and glass transition temperature but higher selectivity than pure PC membranes. Their FTIR spectra were also indicated a possible interaction between PC and compatibilizer.
In conclusion, PC/compatibilizer blend membranes for successful gas separation were prepared. Low molecular weight compounds with multifunctional groups were found to effect membrane properties at low concentration range, 0.5-5 w%.
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Perry, John Douglas. "Formation and characterization of hybrid membranes utilizing high-performance polyimides and carbon molecular sieves." Diss., Available online, Georgia Institute of Technology, 2007, 2007. http://etd.gatech.edu/theses/available/etd-05152007-063433/.
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Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2008.Koros, William J., Committee Chair ; Breedveld, Victor, Committee Member ; Jones, Christopher W., Committee Member ; Kumar, Satish, Committee Member ; Nair, Sankar, Committee Member.
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Kassaee, Mohamad Hadi. "Internal surface modification of zeolite MFI particles and membranes for gas separation." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44906.
Full textAbstract:
Zeolites are a well-known class of crystalline oxide materials with tunable compositions and nanoporous structures, and have been used extensively in catalysis, adsorption, and ion exchange. The zeolite MFI is one of the well-studied zeolites because it has a pore size and structure suitable for separation or chemical conversion of many industrially important molecules. Modification of zeolite structures with organic groups offers a potential new way to change their properties of zeolites, beyond the manipulation of the zeolite framework structure and composition.
The main goals of this thesis research are to study the organic-modification of the MFI pore structure, and to assess the effects of such modification on the adsorption and transport properties of zeolite MFI sorbents and membranes. In this work, the internal pore structure of MFI zeolite particles and membranes has been modified by direct covalent condensation or chemical complexation of different organic molecules with the silanol defect sites existing in the MFI structure. The organic molecules used for pore modification are 1-butanol, 1-hexanol, 3-amino-1-propanol, 1-propaneamine, 1,3-diaminopropane, 2-[(2-aminoethyl)amino]ethanol, and benzenemethanol. TGA/DSC and 13C/29Si NMR characterizations indicated that the functional groups were chemically bound to the zeolite framework, and that the loading was commensurate with the concentration of internal silanol defects. Gas adsorption isotherms of CO2, CH4, and N2 on the modified zeolite materials show a range of properties different from that of the bare MFI zeolite. The MFI/3-amino-1-propanol, MFI/2-[(2-aminoethyl)amino]ethanol, and MFI/benzenemethanol materials showed the largest differences from bare MFI. These properties were qualitatively explained by the known affinity of amino- and hydroxyl groups for CO2, and of the phenyl group for CH4. The combined influence of adsorption and diffusion changes due to modification can be studied by measuring permeation of different gases on modified MFI membranes.
To study these effects, I synthesized MFI membranes with [h0h] out-of-plane orientation on α-alumina supports. The membranes were modified by the same procedures as used for MFI particles and with 1-butanol, 3-amino-1-propanol, 2-[(2-aminoethyl)amino]ethanol, and benzenemethanol. The existence of functional groups in the pores of the zeolite was confirmed by PA-FTIR measurements. Permeation measurements of H2, N2, CO2, CH4, and SF6, were performed at room temperature before and after modification. Permeation of n-butane, and i-butane were measured before and after modification with 1-butanol. For all of the studied gases, gas permeances decreased by 1-2 orders of magnitude compared to bare MFI membranes for modified membranes. This is a strong indication that the organic species in the MFI framework are interacting with or blocking the gas molecule transport through the MFI pores.
A detailed fundamental study of the CO2 adsorption mechanism in modified zeolites is necessary to gain a better understating of the adsorption and permeation behavior of such materials. Towards this end, an in situ FTIR study was performe.For the organic molecules with only one functional group (1-butanol, benzenemethanol, and 1-propaneamine), physical adsorption was found - as intuitively expected - to be the only observed mode of attachment of CO2 to the modified zeolite material. Even in the case of MFI modified with 1,3-diaminopropane, only physical adsorption is seen. This is explained by the isolated nature of the amine groups in the material, due to which only a single amine group can interact with a CO2 molecule. On the other hand, chemisorbed CO2 species are clearly observed on bare MFI, and on MFI modified with 3-amino-1-propanol or 2-[(2-aminoethyl)amino]ethanol. Specifically, these are carbonate-like species that arise from the chemisorption of CO2 to the silanol group in bare MFI and the alcohol groups of the modifying molecule. The possibility of significant contributions from external surface silanol groups in adsorbing CO2 chemisorbed species was ruled out by a comparative examination of the FTIR spectra of 10 μm and 900 nm MFI particles modified with 2-[(2-aminoethyl)amino]ethanol.
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Rose, Lauren. "Carbon Dioxide Gas Separation from Syngas to Increase Conversion of Reverse Water Gas Shift Reaction via Polymeric and Mixed Matrix Membranes." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37897.
Full textAbstract:
Membranes are a promising, effective and energy efficient separation strategy for effluent gases in the Reverse Water Gas Shift (RWGS) reaction to increase the overall conversion of CO2 to CO. This process involves a separation and recycling process to reuse the unreacted CO2 from the RWGS reactor. The carbon monoxide produced from this reaction, alongside hydrogen (composing syngas), can be used in the Fischer-Tropsch process to create synthetic fuel, turning stationary CO2 emissions into a useable resource. A literature review was performed to select suitable polymers with high CO2 permeability and selectivities of CO2 over CO and H2. PDMS (polydimethylsiloxane) was selected and commercial and in-house PDMS membranes were tested. The highest CO2 permeability observed was 5,883 Barrers, including a CO2/H2 selectivity of 21 and a CO2/CO selectivity of 9, with ternary gas feeds. HY zeolite, silica gel and activated carbon were selected from previous research for their CO2 separation capabilities, to be investigated in PDMS mixed matrix membranes in 4 wt % loadings. Activated carbon in PDMS proved to be the best performing mixed matrix membrane with a CO2 permeability of 2,447 Barrers and comparable selectivities for CO2/H2 and CO2/CO of 14 and 9, respectively. It was believed that swelling, compaction and the homogeneity of the selective layer were responsible for trends in permeability with respect to driving force. The HY and silica gel mixed matrix PDMS membranes were believed to experience constraints in performance due to particle and polymer interfaces within the membrane matrix.
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Ma, Canghai. "Highly productive ester crosslinkable composite hollow fiber membranes for aggressive natural gas separations." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50115.
Full textAbstract:
Despite intrinsically high separation performance, conventional polymeric membranes suffer from CO₂ induced plasticization, which reduces CO₂/CH₄ separation efficiency significantly. Covalent ester-crosslinking can improve the plasticization resistance by controlling the segmental chain mobility in the polymer; however, only relatively thick selective skin layers and lower separation productivity have been reported to date. On the other hand, the high cost of crosslinkable polymers makes the approach challenging, especially for large-scale gas separations which require large membrane areas with high feed pressures. Dual-layer hollow fiber spinning can be used to reduce the cost of membrane production by integrating a low-cost supporting core polymer with the expensive crosslinkable sheath polymer. However, the complexity of interfacial interaction between the sheath/core layers and subsequent crosslinking required can delaminate the sheath/core layers and collapse the core layer polymer. This can reduce mechanical strength and the separation productivity significantly. This work aimed to develop thin-skinned high-performing ester-crosslinked hollow fiber membranes with improved CO₂ plasticization resistance. The skin layer thickness of hollow fibers was first optimized by simultaneous optimization of the polymer dope and spinning process variables. Moreover, this study also addresses the solutions of challenging in transitioning the monolithic hollow fiber to composite hollow fiber format. The ester-crosslinked hollow fibers were subjected to high feed pressures and high-level contaminants to probe their CO₂ plasticization and hydrocarbon antiplasticization resistance, respectively. The resultant ester-crosslinked monolithic hollow fibers show significantly reduced skin layer thickness and improved separation productivity under extremely challenging operation conditions. They also demonstrate strong stability under high feed pressures and reversibility after contaminant exposure. Moreover, this study presents a newly discovered core layer material, Torlon®, which demonstrates excellent compatibility with the crosslinkable polymer and superior thermal stability during crosslinking without sheath/core layer delamination or collapse. The characterization under aggressive feed conditions clearly suggests that ester-crosslinked composite hollow fibers can achieve high separation performance and reduce membrane cost simultaneously. This provides a significant advance in state of the art for natural gas separations under realistic operation environments
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Zimmerman, Catherine Mary. "Advanced gas separation membrane materials : hyper rigid polymers and molecular sieve-polymer mixed matrices /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Schulte, Leslie. "Blending high performance polymers for improved stability in integrally skinned asymmetric gas separation membranes." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19121.
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Doctor of PhilosophyDepartment of Chemical Engineering
Mary E. Rezac
Polyimide membranes have been used extensively in gas separation applications because of their attractive gas transport properties and the ease of processing these materials. Other applications of membranes, such as membrane reactors, which could compete with more traditional packed and slurry bed reactors across a wider range of environments, could benefit from improvements in the thermal and chemical stability of polymeric membranes. This work focuses on blending polyimide and polybenzimidazole polymers to improve the thermal and chemical stability of polyimide membranes while retaining the desirable characteristics of the polyimide. Blended dense films and asymmetric membranes were fabricated and characterized. Dense film properties are useful for studying intrinsic properties of the polymer blends. Transport properties of dense films were characterized from room temperature to 200°C. Properties including miscibility, density, chain packing and thermal stability were investigated. A process for fabricating flat sheet blended integrally skinned asymmetric membranes by phase inversion was developed. The transport properties of membranes were characterized from room temperature to 300°C. A critical characteristic of gas separation membranes is selectivity. Post-treatments including thermal annealing and vapor and liquid surface treatments were investigated to improve the selectivity of blended membranes. Vapor and liquid surface treatments with common, benign solvents including an alkane, an aldehyde and an alcohol resulted in improvements in selectivity.