Дисертації з теми "Molecular separation"
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1
Chagger, Harnit Kaur. "Carbon molecular sieves for air separation." Thesis, University of Newcastle Upon Tyne, 1994. http://hdl.handle.net/10443/851.
Анотація:
Carbon is one of the naturally occurring elements and has an atomic weight 12.01 atomic mass units (amu) and atomic number 6. It has six electrons and has an electronic configuration of: ls2 2S2 1p2 in the ground state. This element exists in different crystalline forms-diamond, graphite, buckminsterfullerene1 and carbyne2. Carbon also has the ability of catenation via formation of σ and π bonds.
2
Briceño, Mejías Kelly Cristina. "Carbon molecular sieve membranes for gas separation." Doctoral thesis, Universitat Rovira i Virgili, 2012. http://hdl.handle.net/10803/145378.
Анотація:
Membrane separations are simple, energy efficient processes, which can be economically competitive with traditional separation technologies. In the case of gas separation both dense and porous materials have been developed for different application where hydrogen production is one of the most important niches of development. Hydrogen is being one of the most important vectors to develop alternative clean power generation sources. Nowadays, a lot of processes require the fabrication of pure hydrogen for efficiency and better performance. Different materials have been reported as gas separation membranes but still numerous problems related to stability, cost and fabrication must be overcome. The actual goal is to achieve materials that report good separation properties in new type of configuration facing industrial applications.
Carbon molecular sieve membranes (CMSM) achieve high separation factors and permeance values than polymeric membranes. During the last 30 years they have gained importance due to their excellent performance as gas separation membranes. However, most research work has been focused on flat or hollow fiber configurations and minor attention has been done to supported CMSM. The main reason is due the difficulties associated to fabricate a defect free membrane using a highly reproducible fabrication method that allow to obtain a carbon layer after one polymer precursor coating step. In tubular configuration, these hybrid membranes are suitable for scaling up towards industrial applications, being more competitive than commercial unsupported hollow fiber membranes and films, especially under high pressure and temperature.
The main objective of this work was to explore alternative fabrication methods for the fabrication of supported CMSM. In order to achieve this objective polyimide was coated over inorganic supports using two different approaches. The two methods reported in this thesis were spinning-coating and dip-coating. The idea of spinning¬coating was adapted from fabrication of supported carbon planar film. In this work it was developed the same idea coating TiO2 tubular supports under rotation with polyimide (Matrimid®). The thickness of the carbon membranes was controlled adjusting the viscosity of the polymeric solution, and after an exhaustive solvent
i
elimination it was possible to obtain a defect free carbon membrane. The influence of methanol washing, pyrolysis temperature (550-700ºC), and presence of the support allowed to extracting conclusions about the characteristics of the carbon material. Single gas permeance of H2, CO, CO2, N2, CH4 were obtained and ideal selectivity computed from this measurements indicated the presence of pinholes on the carbon membrane. However, the characterization of this carbon obtained after 550º and 700º C by adsorption-desorption analysis allowed to confirm the microporosity of the carbon layer. As an important contribution of this work the influence of the support as pore modifier of the carbon structure is presented after analysis of supported and unsupported samples. Different characterization techniques are presented and integrated in this work to analyze the microporous character of the carbon layer (immersion calorimetry, AFM) and to evaluate the mesoporous characteristics of the asymmetric membrane (liquid-liquid displacement porosimetry). An additional coating procedure with polydimethylsiloxane (PDMS) was performed to decrease the influence of pinholes which caused a permeance decrease but increase on ideal selectivity values over Knudsen theoretical index.
As a second fabrication technique, the modification of Al2O3 inorganic support allowed to achieve microporosity in the support that allowed the fabrication of CMSM by dip¬coating procedure. Similarly to the dip-coating method, viscosity and polymer concentration were optimized in order to achieve high ideal separation factors for hydrogen pairs. For the type of membranes obtained by this method single gas permeance of H2, He, CO2, O2, N2, CH4, Propane, n-butane, 1-butene, SF6 was performed. Influence of pyrolysis temperature, aging, non-solvent immersion, and support were also studied as pore modifier of the carbon membrane. However, for these membranes the characterization was focused on the effect on permeance and selectivity more than in the characterization of the material.
The findings described in this PhD thesis open new perspectives for alternative fabrication techniques of CMSM. This work reports not only the permeance and selective properties of CMSM as the traditional approaches rule. Moreover, brings how each fabrication variable could affect the final properties of the membrane. Integration of structure and properties are presented as an alternative strategy to design new pore architecture on CMSM.
3
Klimczyk, Malgorzata. "Separation of hexane isomers using molecular sieves." Thesis, De Montfort University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.697435.
4
Luo, H. "A molecular dynamic study of molecular gas separation for clean energy applications." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1532033/.
Анотація:
Gaseous molecular separation is crucial for carbon dioxide capture and storage, hydrogen purification, and natural gas processing. Graphene-based membranes are promising candidates for such purposes, where their performance can be enhanced by the tunable pathways consisting of the nanopore, interlayers and inter-edge spacing. However, there is a lack of understanding of the molecular behaviours within the versatile pathways, due to the practical complexity of the process and the limitation of experimental techniques. Molecular Dynamics (MD) simulations can offer significant insights into the mechanisms of molecular transport characteristics inside graphene-based nanostructures, and hence predict the membrane performance and optimisation for gas separations. A newly proposed monolayer porous graphene membrane was first evaluated as a primary step for the separation of H2 from CH4, N2, or CO2 impurities. The membrane showed high performance for the H2/CH4 separation under various pressure gradients; with the selectivity-permeance relationship far surpassing the upper bound for conventional polymer membranes. For H2/N2 separation, the selectivity-permeance relationship closely approached the upper bound. For H2/CO2 separation, CO2 molecules can be strongly adsorbed at the centre of the porous membrane, implying that the membrane can also function as a highly selective sorbent for CO2 removal. Furthermore, the characteristics of CO2 and N2 diffusion inside different interlayer spaces of graphene-based membranes were investigated under both dry and iii wet conditions. Based on the solution-diffusion mechanism, the predicted selectivity of CO2/N2 separation was improved 42 times by the presence of water, as a result of the single-file diffusion of CO2 through the interlayers of graphenebased structures; this could help explain the experimental observations in the literature. An in-depth investigation into the mechanism of the enhancement on the selectivity of CO2/N2 separation showed that water formed hydrogen bond networks with rich oxygen-containing groups of graphene-based membranes and restricted the diffusion of CO2 and N2, leading to the self-diffusivity of CO2 and N2 approximating to that of H2O. Under the confinement of graphene-based interlayer spaces, the solubility of both CO2 and N2 were improved, with the solubility of CO2 being larger than that of N2 due to the stronger binding between oxygen-containing groups and CO2 than N2. Finally, the diffusion of H2, CH4, CO2 and CO through the inter-edge spacing of graphene-based membranes was investigated. The results showed that high selectivity and permeance for CO2 removal from H2, CH4, CO impurities were achieved by modifying the chemistry of the inter-edge spacing of the graphene-based membrane. The highest enhancement is 136% for H2/CO2, 208% for CH4/CO2, and 180% for CO/CO2 separations when the edges were enriched with carboxyl groups. Much of the enhancement was due to the presence of carboxyl and amide groups which forced gases to diffuse in a larger distance from the edges of graphene-based structures, where H2, CH4, CO showed higher mobility, except for CO2 due to its strong binding with various functional groups. This study provides a fundamental understanding of gas transport characteristics through the complex pathways of graphene-based nanostructures and is of great significance to practical design and development of membranes for gas separations.
5
Kulkarni, Amit. "Reaction induced phase-separation controlled by molecular topology.*." Cincinnati, Ohio : University of Cincinnati, 2004. http://www.ohiolink.edu/etd/view.cgi?acc%5Fnum=ucin1108001435.
6
Triebe, Robert W. "Separation and purification of gases with molecular sieves." Thesis, University of Ottawa (Canada), 1994. http://hdl.handle.net/10393/9657.
Анотація:
Equilibrium adsorption constants were determined for CO, CO$\sb2$, NO, N$\sb2$, CH$\sb4$, C$\sb2$H$\sb4$, and C$\sb2$H$\sb6$ on various molecular sieves between 233 and 523 K. The molecular sieves tested for adsorption of these gases were 4A and 5A zeolite, 13X and a CaX zeolite, H-mordenite, a natural clinoptilolite and a carbon molecular sieve. The gas chromatographic method was used for all equilibrium measurements. Upon choosing the promising CO/N$\sb2$/clinoptilolite system for further studies, kinetic (diffusion) characteristics of each of these pure gases in the clinoptilolite ports was examined between 323 and 423 K using the gas chromatographic method. Pure gas and binary gas adsorption isotherms for the CO/N$\sb2$/clinoptilolite system were determined up to 1 atmosphere pressure at 303 K using the gas chromatographic method. Pure isotherms were fit with the Lanpmuir and Vacancy Solution Theory models. Pure gas modelling results were used to predict and compared to the experimentally determined binary gas isotherms. Separation of polar compounds from non-polar compounds was facilitated by inclusion of divalent cations in the zeolite micropores. Clinoptilolite showed great promise for various separations. The chromatographic method for measuring adsorption isotherms is limited in the measurement of rectangular isotherms, yielding errors dependant upon the accuracy of the gas blending system. The Wilson form of the VST accurately predicts the binary adsorption data.
7
Khajavi, Sheida, Freek Kapteijn, and Johannes Carolus Jansen. "Separation based on molecular level using zeolitic membranes." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194860.
8
Khajavi, Sheida, Freek Kapteijn, and Johannes Carolus Jansen. "Separation based on molecular level using zeolitic membranes." Diffusion fundamentals 3 (2005) 22, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14313.
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KULKARNI, AMIT S. "REACTION INDUCED PHASE-SEPARATION CONTROLLED BY MOLECULAR TOPOLOGY." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1108001435.
10
Ning, Xue. "Carbon molecular sieve membranes for nitrogen/methane separation." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53986.
Анотація:
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.
11
Song, Qilei. "Polymer molecular sieve membranes." Thesis, University of Cambridge, 2014. https://www.repository.cam.ac.uk/handle/1810/280264.
Анотація:
Sustainable energy supply and environmental protection are the major global scientific challenges in the 21st century, such as greenhouse gas capture, natural gas production, desalination of seawater for clean water production. Membrane separation technology offers attractive energy-efficient and environmental-friendly solutions to these challenges. This PhD thesis is focused on design and fabrication of membranes from novel molecularly defined polymers and understanding their physical properties, particularly the transport properties of gas molecules in polymer membranes. First, we demonstrate a simple approach of fabricating novel polymer nanocomposite membranes using established colloidal science. Crystalline microporous zeolitic imidazolate frameworks (ZIFs) nanocrystals are incorporated into a polyimide polymer matrix via solution mixing. The resulting nanocomposite membranes show excellent dispersion of nanoparticles, good adhesion at the interface, and enhanced gas permeability while the selectivity remain at high level. We then fabricated membranes from novel microporous polymers, polymers of intrinsic microporosity (PIMs). Using the PIM-1 polymer as a prototype, we discovered that ultraviolet irradiation of PIM-1 membranes in the presence of oxygen induces oxidative chain scission at the surface, resulting in local densification and structural transformation of free volume elements. Consequently, the membrane become asymmetric with a more gas-selective layer formed at the surface, while the overall permeability maintains at high level. Finally, we report a simple thermal oxidative crosslinking method to tailor the architecture of channels and free volume elements in PIM-1 polymer membrane by heat treatment in the presence of trace amounts of oxygen molecules. The resulting covalently crosslinked polymer networks offer superior thermal stability, chemical stability, reasonable mechanical strength, and enhanced rigidity. Most important of all, thermally crosslinked PIM-1 polymer membranes show significantly enhanced molecular sieving functions that yield remarkably high selectivity and high gas permeability, which surpass the upper bound that has been limiting the polymer membranes for decades. We also demonstrate that the thermal crosslinking method is effective for crosslinking of nanocomposite membranes with porous or nonporous fillers. These microporous molecular sieve membranes are promising for a wide range of molecular-level separation applications.
12
Kiyono, Mayumi. "Carbon molecular sieve membranes for natural gas separations." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42798.
Анотація:
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.
13
Kemmerlin, Ruben Kyle. "Carbon molecular sieve membranes for aggressive sour gas separations." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50135.
Анотація:
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.
14
Xu, Liren. "Carbon molecular sieve hollow fiber membranes for olefin/paraffin separations." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50130.
Анотація:
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.
15
Williams, Paul Jason. "Analysis of factors influencing the performance of CMS membranes for gas separation." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-05082006-082322/.
Анотація:
Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007.Teja, Amyn, Committee Member ; Koros, William, Committee Chair ; Jones, Christopher, Committee Member ; Nair, Sankar, Committee Member ; Kumar, Satish, Committee Member.
16
Gopinath, Smitha. "Molecular design, process design and process synthesis of separation systems." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/59004.
Анотація:
The simultaneous solution of the optimal process variables and optimal processing materials for a separation system is considered in this work. The processing materials (or molecules) may include, amongst others, reaction medium solvents, catalysts and mass separating agents. In this thesis, the processing materials to be designed are restricted to pure component solvents that act as mass separating agents. The design of fluid-fluid separation systems at steady state is considered in this work. In the first part of the thesis, the process topology is fixed and the process variables are continuous whereas the molecular variables, used to describe the solvent, are discrete. The computer aided molecular and process design problem (CAMPD) is a challenging mixed integer nonlinear programming problem (MINLP). A deterministic optimization algorithm tailored to the CAMPD of separation systems is proposed. Novel tests are embedded within an iterative MINLP solution framework. The tests may eliminate infeasible regions of both the molecular and process domain. The algorithm is applied to a case study of separation of carbon dioxide and methane. In the second part of the thesis, the scenario where the process variables are both continuous and discrete is considered. Chemical process synthesis is the activity of determining the optimal process units and their connectivity in a process. Process synthesis is a highly combinatorial problem which is challenging, even with fixed material decisions. A formulation for process synthesis problems is presented which addresses numerical singularities that are encountered when a process unit is not selected. The computer aided molecular and process synthesis (CAMPS) problem is considered next where the degrees of freedom include material and process synthesis decisions. An algorithm for CAMPS is developed by extending the CAMPD algorithm. A CAMPS case study of separation of butanol and water is modelled using the process synthesis formulation developed in this thesis. The tests can eliminate infeasible portions of the molecular domain and both continuous and discrete process domains. Both the CAMPD and CAMPS algorithms proposed here avert evaluations of infeasible primal problems and enhance convergence to solutions of challenging design problems.
17
Au, Harold (Harold S. ). "Molecular dynamics simulation of nanoporous graphene for selective gas separation." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78180.
Анотація:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 71-76).
Graphene with sub-nanometer sized pores has the potential to act as a filter for gas separation with considerable efficiency gains compared to traditional technologies. Nanoporous graphene membranes are expected to yield high selectivity through molecular size exclusion effects, while achieving high permeability due to the very small thickness of graphene. In this thesis, we model the separation of gas components from a mixture using a graphene sheet with engineered pores of different sizes. We employ molecular dynamics simulations to calculate a large number of molecular trajectories, and thus obtain low-statistical-uncertainty estimates of transport rates through the membrane. Simulations are performed on two different gas mixtures - a helium-sulfur hexafluoride mixture, for which the large difference in molecular size lends itself to a size-based separation approach, and a hydrogen-methane mixture, which is relevant to natural gas processing. Our simulations show that graphene membranes with large pores are permeable to both gases in the mixture. As pore sizes are reduced, we observe a greater decrease in the permeability of the larger species that results in a molecular size exclusion effect for a range of pore sizes that are still permeable to the smaller species. This indicates that a pore size can be determined that achieves high selectivity in gas separation, while exhibiting high permeability for the desired gas species. We expect this work to form the basis for the design of an energy-efficient graphene-based gas separation device. The simulation-based approach described here can be very useful for guiding experimental efforts which are currently limited by the difficulty associated with creating pores of a specific size in otherwise pristine graphene.
by Harold Au.
S.M.
18
Corcoran, Edward W., Ronald R. Chance, Harry W. Deckman, Gregory J. DeMartin, Sebastián C. Reyes, C. J. Yoon, and Trevor E. Clark. "Molecular transport in inorganic membranes: CO 2 /CH 4 separation." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194810.
19
Corcoran, Edward W., Ronald R. Chance, Harry W. Deckman, Gregory J. DeMartin, Sebastián C. Reyes, C. J. Yoon, and Trevor E. Clark. "Molecular transport in inorganic membranes: CO 2 /CH 4 separation." Diffusion fundamentals 3 (2005) 18, S. 1, 2005. https://ul.qucosa.de/id/qucosa%3A14307.
20
Grommet, Angela B. "Coordination cages for the separation and transportation of molecular cargo." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274998.
Анотація:
The first chapter of this thesis introduces the fundamental concepts governing the design and synthesis of supramolecular complexes. By illustrating the synthesis of several coordination cages reported in the literature, the principles underlying the construction of coordination cages by subcomponent self-assembly are elucidated. Ionic liquids are then proposed as solvents for cage systems; general methods for the preparation and synthesis of these solvents are described. The second chapter explores the use of ionic liquids as solvents for existing coordination cages. Potential methods of characterising these cages in ionic liquids are discussed; cages are demonstrated to be stable and capable of encapsulating guests in these ionic environments; and systems in which cages have good solubility in ionic liquids are designed. Building upon these observations, a triphasic sorting system is presented such that each of three different host-guest complexes are soluble in only one of three immiscible liquid phases. In contrast to the static triphasic system described in the second chapter, the third chapter explores directed phase transfer of coordination cages and their cargos from water, across a phase interface, and into an ionic liquid phase. The host-guest complex can then be recycled from the ionic liquid layer back into water after several additional steps. Furthermore, phase transfer of cationic cages is used to separate a mixture of cationic and anionic host-guest complexes. In the fourth chapter, fully reversible phase transfer of coordination cages is developed. Using anion exchange to modulate the solubility of three different cationic cages, reversible transport between water and ethyl acetate is demonstrated. Sequential phase transfer can also be achieved such that, from a mixture of cubic (+16) and tetrahedral (+8) cages, the cubic cage transfers from water to ethyl acetate before the tetrahedral cage. This process is fully reversible; upon the addition of a hydrophilic anion, the tetrahedral cage returns from ethyl acetate to water before the cubic cage.
21
Kang, Dun-Yen. "Single-walled metal oxide nanotubes and nanotube membranes for molecular separations." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44715.
Анотація:
Synthetic single-walled metal oxide (aluminosilicate) nanotubes (SWNTs) are emerging materials for a number of applications involving molecular transport and adsorption due to their unique pore structure, high surface reactivity, and controllable dimensions. In this thesis, I discuss the potential for employing SWNTs in next generation separation platforms based upon recent progress on synthesis, interior modification, molecular diffusion properties, transport modeling and composite membrane preparation of metal oxide SWNTs. First, I describe the structure, synthesis, and characterization of the SWNTs. Thereafter, chemical modification of the nanotube interior is described as a means for tuning the nanotube properties for molecular separations. Interior functionalization of SWNTs (e.g. carbon nanotubes and metal oxide nanotubes) is a long-standing challenge in nanomaterials science. After controlled dehydration and dehydroxylation of the SWNTs, I then demonstrate that the SWNT inner surface can be functionalized with various organic groups of practical interest via solid-liquid heterogeneous reactions. Finally, I describe a mass transport modeling and measurements for composite membranes composed of SWNTs as fillers. This work demonstrates the use of SWNTs for novel scalable separation units from both a nanoscale and a macroscale point of view.
22
Inman, Christina Elizabeth. "Stability and phase separation in peptide containing alkanethiol monolayers /." view abstract or download file of text, 2005. http://wwwlib.umi.com/cr/uoregon/fullcit?p3201684.
Анотація:
Thesis (Ph. D.)--University of Oregon, 2005.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 236 - 249). Also available for download via the World Wide Web; free to University of Oregon users.
23
Bahamón, García Daniel. "New generation adsorbents for gas separation: from modeling to industrial application." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/325690.
Анотація:
Teniendo en cuenta el rápido aumento de la población y el crecimiento en el consumo de energía como consecuencia de grandes progresos en transporte y tecnología, el desarrollo sostenible es de especial relevancia pues sugiere la búsqueda de formas de mitigar las emisiones de gases de efecto invernadero, incluyendo la captura y almacenamiento de carbono (o utilización), la eficiencia energética, fuentes alternativas de energía y ahorro de energía, como ya se ha sugerido por el protocolo de Kioto y los informes del IPCC. De ahí que en los últimos años se haya dedicado un esfuerzo considerable a desarrollar tecnologías para la captura y almacenamiento de CO2 a partir de fuentes concentradas de emisión.
Además de establecer nuevas tecnologías, durante las últimas décadas la ciencia de materiales sólidos porosos se ha convertido en una de las áreas más intensas de investigación y desarrollo para químicos, físicos y científicos de materiales. De hecho, se ha avanzado considerablemente en el desarrollo de nuevos adsorbentes para diversos procesos de separación. Por ejemplo, las estructuras órgano-metálicas (MOFs) han ido ganando considerable atención como materiales prometedores para aplicaciones de almacenamiento y separación de gases, debido a sus propiedades excepcionales. Sin embargo, es necesaria una comprensión a nivel molecular de la adsorción de gases para acelerar el diseño y desarrollo de aplicaciones a la carta. También es fundamental conocer el comportamiento bajo condiciones de humedad e impurezas, como se tiene normalmente en aplicaciones industriales específicas.
El trabajo desarrollado en esta Tesis Doctoral destaca el uso de técnicas de simulación molecular para la optimización de procesos relacionados con el medio ambiente. El objetivo general se centra en avanzar en el campo de materiales para la captura y separación de dióxido de carbono a condiciones de proceso. Se considera de manera explícita la influencia del vapor de agua e impurezas, tanto a la luz de los fundamentos de la adsorción como en la aplicación para la captura de CO2 por post-combustión mediante ciclos de adsorción por oscilación.
Partiendo de una breve descripción de los fundamentos de la adsorción y de las simulaciones moleculares, se presenta una revisión exhaustiva de estudios recientes de materiales para captura y separación de CO2, proporcionando así información valiosa para su aplicación industrial. Basados en esta revisión, se han estudiado en detalle algunos de los materiales más prometedores para un proceso de adsorción por cambio de temperatura (TSA) basado en simulaciones moleculares, proponiéndose un nuevo procedimiento para la evaluación y optimización de los sistemas de captura en condiciones reales. Dada la gran influencia de trazas de agua en la separación, se investiga también el CuBTC (uno de los MOF más estudiados y estables en agua) en comparación con la zeolita de referencia 13X. Se examina en detalle el efecto de las especies coexistentes, así como la influencia del agua y SO2 en los gases de combustión, con el fin de llegar a una mejor comprensión de la capacidad de adsorción, la selectividad, la localización de las moléculas en el material, las distribuciones de calor isostérico y su relación con el proceso.
Asimismo, se han llevado a cabo estudios paramétricos detallados para una investigación comparativa de la separación de mezclas multi-componentes de gases de combustión mediante el uso de otras zeolitas como caolinita y chabacita. Y finalmente, se presenta un trabajo adicional relacionado con otro problema medioambiental: la separación de un contaminante (ibuprofeno) en agua, mediante el uso de carbones activados, usando las mismas técnicas computacionales, demostrando así la versatilidad de las herramientas empleadas para este tipo de sistemas.Given the rapid increase in population and the growth in energy consumption as a consequence of major developments in transportation and technology, sustainable development is of special relevance, suggesting ways to mitigate greenhouse gases emissions, including carbon capture and storage (or utilization, CCSU), energy efficiency, alternative energy sources and energy savings, as already suggested by the Kyoto’s Protocol and the IPCC reports. Hence, much effort has been devoted in recent years to develop technologies for capture and storage of CO2 from concentrated sources of emission. Apart from establishing new technologies, over the last decades the science of porous solid materials has become one of the most intense areas of research and development for chemists, physicists, and materials scientists. In fact, considerable progress has been made in recent years on the development of novel adsorbents. For instance, Metal Organic Frameworks (MOFs) have been gaining considerable attention as promising nanoporous materials for gas storage and gas separation applications due to their exceptional physical and chemical properties, and have already been demonstrated to be promising materials in the separation of different gases, however, a molecular level understanding of gas adsorption in the pores is crucial to accelerate the design and development of these and other applications. It is also fundamental to know their behavior under moisture conditions and impurities content, as normally found at specific industrial applications. The work developed in this Thesis highlights the use of molecular simulation techniques for optimizing environmental related processes, providing new procedures to assess the use of these materials from their fundamental knowledge until their applications at industrial conditions. The overall objective is to advance in the field of materials for CO2 capture and separation at process conditions. The influence of water vapor and impurities is explicitly considered, both, in the light of the fundamentals of adsorption and in the application for post-combustion carbon dioxide capture by swing adsorption cycles. Starting from a brief description of the fundamentals of adsorption and molecular simulations, a novel throughout review on recent studies of materials for CO2 capture and separation is presented, thus providing valuable information to assess their industrial application. Based on this review, some of the most promising materials for CO2 separation in a Temperature Swing Adsorption (TSA) process have been studied in detail by using molecular simulations (compared to experimental data when available), proposing a new process for the evaluation and optimization capture systems under real conditions. In addition, given the great influence of water as a trace compound on the separation, CuBTC (one of the most studied MOFs, stable in water and with potential for industrial application) has been investigated in comparison to the benchmark zeolite 13X. The effect of the coexisting species as well as the influence of water and SO2 in flue gas is examined in detail in order to reach a better understanding of the adsorption capacity, selectivity, adsorption density location and isosteric heat distributions. And finally, detailed parametric studies have been carried out for a comparative computational investigation for separating of multi-component mixtures of flue gas by using other representative zeolites such as kaolinite and chabazite. Additional work, related to another environmental problem: the separation of a pollutant (ibuprofen) in water, by using activated carbons, is also presented here, demonstrating the versatility of the tools used for these types of systems.
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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.
Анотація:
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.
25
Deschler, Felix. "How molecular doping affects the charge separation process in polymer-fullerene blends." Diss., lmu, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-153170.
26
Zoroufchian, Moghadam Peyman. "Molecular simulation studies of gas adsorption and separation in metal-organic frameworks." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7595.
Анотація:
Adsorption in porous materials plays a significant role in industrial separation processes. Here, the host-guest interaction and the pore shape influence the distribution of products. Metal-organic frameworks (MOFs) are promising materials for separation purposes as their diversity due to their building block synthesis from metal corners and organic linker gives rise to a wide range of porous structures. The selectivity differs from MOF to MOF as the size and shapes of their pores are tuneable by altering the organic linkers and thus changing the host-guest interactions in the pores. Using mainly molecular simulation techniques, this work focuses on three types of separations using MOFs. Firstly, the experimental incorporation of calix[4]arenes in MOFs as a linker to create additional adsorption sites is investigated. For a mixture of methane and hydrogen, it is shown that in the calix[4]arene-based MOFs, methane is adsorbed preferentially over hydrogen with much higher selectivities compared to other MOFs in the literature. Remarkably, it was shown that extra voids created by calix[4]arene-based linkers, were accessible to only hydrogen molecules. Secondly, the strong correlation between different pore sizes and shapes in MOFs and their capabilities to separate xylene isomers were investigated for a number of MOFs. Finally, the underlying molecular mechanism of enantioseparation behaviour in a homochiral MOF for a number of chiral diols is presented. The simulation results showed good agreement with experimental enantioselectivity values. It was observed that high enantioselectivity occurs only at high loadings and when a perfect match in terms of size and shape exists between the pore size and the adsorbates. Ultimately, the information obtained from molecular simulations will further our understanding of how network topology, pore size and shape in MOFs influence their performance as selective adsorbents for desired applications.
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Ismail, Ahmad Fauzi. "Novel studies of molecular orientation in synthetic polymeric membranes for gas separation." Thesis, University of Strathclyde, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249863.
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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.
Анотація:
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.
29
Jackson, George. "Phase separation in solutions of large spherical particles." Thesis, University of Oxford, 1986. http://ora.ox.ac.uk/objects/uuid:9db7de2e-b365-4433-8e14-746efb32c070.
Анотація:
The effect of large size ratios of solute to solvent on the critical properties and phase behaviour of binary mixtures of spherical particles is investigated using an "augmented van der Waals" equation of state. The equation used is essentially a van der Waals equation with an improved hard sphere repulsive term. Molecular dynamics and constant-pressure Monte Carlo simulations of binary mixtures of hard spheres with different diameter ratios and mole fractions are undertaken to check the adequacy of the hard sphere equation. Good agreement is found, even for systems with large differences in size. Furthermore, many of the hard sphere mixtures exhibited a transition from a fluid to a solid phase at high densities. Phase boundaries are calculated for model mixtures comprising spheres of different sizes between which there are long-ranged attractive forces. Particular attention is paid to the case in which the ratio of sizes is infinite. The systems show a wide variety of behaviour that includes liquid-liquid and gas-gas immiscibility, and the formation of negative azeotropes. Calculations investigating the effect of different attractive interactions between the small and large spheres show that as the magnitude of this interaction is increased, liquid-liquid immiscibility becomes the dominant feature of the phase diagram at moderate temperatures. The extent of liquid-liquid coexistence is greatest at large size differences. These model systems are shown to reproduce some of the behaviour of aqueous solutions of surfactants if it is assumed that the large spheres are models of the micelles and the small spheres models of the solvent molecules. The properties of binary lattice mixtures of bifunctional molecules whose ends are chosen to mimic surfactant and solvent molecules are also briefly investigated, to determine the effect of the asymmetric surfactant molecule on the phase separation. Closed-loops emerge in the phase diagrams as the surfactant character of one of the species is increased.
30
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.
31
Mohanty, Sanat. "Theory and simulations of molecular self-assembly : applications in separation and materials design /." Diss., ON-CAMPUS Access For University of Minnesota, Twin Cities Click on "Connect to Digital Dissertations", 2001. http://www.lib.umn.edu/articles/proquest.phtml.
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Kurdi, Jamal. "Molecular engineering and nanostructuring of polymer networks for high performance gas separation membranes." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/28990.
Анотація:
The architecturing and characterization of polymer-based materials at a molecular scale are of great importance in the development of novel rigid polymeric molecular sieves for high performance gas separation membranes. The new rapidly growing field of nanoscience technologies and material nanostructuring offers novel ways for creating nanoengineered material combinations. Intermolecular and supramolecular interactions among different molecules and clusters play an important role in the microscopic behavior of molecular architectures and molecular self-assembly. In this work, the coordination shell number of polyetherimide (PEI) membranes was determined from experimental X-ray diffraction data and found to be a key link between microscopic pair intermolecular interactions and macroscopic scale interactions. This link enabled us to determine the intermolecular force parameters required to understand material structuring at a molecular scale. These physical parameters are required in all models used in the determination of the micropore size distributions from gas adsorption isotherms.
Computational chemistry and physicochemical principles were useful to illustrate molecular architecturing and coordinating to form intermediate stable molecular complexes during membrane fabrication. These coordination complexes acted as pore forming templates that could be disrupted and removed after polymer coagulation to open the closed PEI network structure and increase the interconnectivity and accessibility among polymer micropores. Based on nanotechnology concepts, a uniform dispersion of nanoscopically-sized filler particles into a polymer network created novel materials with superior properties and characteristics attributed to the presence of ultra-large interfacial area per unit volume. The adhesive (noncovalent interactions among different molecules) properties of nanoelement surfaces and polymer surfaces were the key for the creation of uniform polymeric molecular sieves. Narrowing the micropore size distribution is also possible when the adhesive energy between nanoparticles and polymer phase exceeds the cohesive energy of the pure polymer. Membranes were prepared using twelve metal-ligand complexes as filler additives that were uniformly dispersed into the PEI polymer solution before membrane casting. Membranes containing cobalt phthalocyanine (CoPc) showed the highest performance for oxygen separation from air. However, the performance was largely decreased upon annealing indicating a low nanostructure stability. (Abstract shortened by UMI.)
33
HU, NAIPING. "MOLECULAR SIMULATION OF POLYPHOSPHAZENES AS GAS SEPARATION AND DIRECT METHANOL FUEL CELL MEMBRANES." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1068675414.
34
Guo, Juncheng. "Molecular Simulation Study of Transport and Separation of Gas through Nanoporous Graphene Membranes." Thesis, Pau, 2020. http://www.theses.fr/2020PAUU3029.
Анотація:
Les graphènes nanoporeux gagnent l’attention des industriels dans le domaine des procédés de séparation. En ce qui concerne la séparation des gaz, les techniques s’appuyant sur des membranes perm-sélectives consomme moins d'énergie que les autres technologies conventionnelles. En raison de l'épaisseur atomique du graphène nanoporeux, de la taille contrôlable des pores de l’ordre des diamètres moléculaires, de sa stabilité mécanique et chimique, il est considéré comme l'un des matériaux de membrane les plus favorables pour les applications de séparation des gaz à l’échelle industrielle. Par exemple, dans le contexte de la production de gaz naturel et de la séparation de l'air, la séparation des mélanges CH4/CO2, N2/O2 bénéficierait largement de ce type de nouveaux matériaux. Avec le développement rapide des techniques de fabrication du graphène, des avancées majeures dans la mise en oeuvre de ces membranes sont attendues dans les prochaines années et des données suffisantes peuvent être trouvées dans la littérature scientifique. Toutefois, il n'existe pas de théorie précise permettant de prédire de manière quantitative la perméance des gaz et le facteur de séparation.Dans ce travail, nous montrons que la perméation des gaz à travers les membranes de graphène nanoporeux mono-couche peut être divisée en trois régimes : le tamisage moléculaire, un régime de transition et le régime d’effusion. Nous proposons un cadre théorique pour expliquer les mécanismes et prédire le coefficient de transport diffusif. Dans notre formalisme théorique, le coefficient de transport est lié aux paramètres qui peuvent être calculés à partir du potentiel de force moyenne (PMF) entre les molécules de gaz diffusantes et les atomes de la membrane. Au moyen de simulations de dynamique moléculaire en équilibre (EMD) et en non-équilibre (NEMD), nous explorons la perméance de composés purs à travers des membranes de graphène nanoporeux présentant des pores de taille et de géométrie différentes. Nous étudions également l'effet des conditionsthermodynamiques (pression et température) sur le coefficient de transport. Les coefficients de transport simulés sont en bon accord avec les prédictions de notre théorie et ce pour tous les régimes de perméation. En outre, sur la base des connaissances acquises sur la perméance des composés purs, nous définissons le concept de sélectivité. En comparant les résultats des simulations moléculaires réalisées avec des mélanges de gaz, nous montrons dans quels cas les résultats obtenus pour les composés purs, et par conséquent notre cadre théorique, nous permettent de prédire la sélectivité des mélangesNanoporous graphene membranes are gaining attention in the field of separation processes. Regarding gas separation, perm-selective membranes technology consumes less energy than other conventional technologies. Due to nanoporous graphene’s atomic thickness, controllable pore size in the range of molecular diameters, mechanical and chemical stability, it is considered as one of the most favorable membrane material for industrial gas separation applications. For instance, in the context of natural gas production and air separation, the separation of CH4/CO2, N2/O2 mixtures would greatly benefit from this kind of new materials. With the rapid development in graphene fabrication technology, breakthroughs in nanoporous graphene membranes are expected in the next few years and quite sufficient data can be found in publications. However,there is no accurate theory that can predict gas permeation and separation factor quantitively.In this work, we show that gas permeation through single-layer nanoporous graphene membranes can be divided into three regimes: molecular sieving, crossover regime and effusion. We propose a theoretical framework to explain the mechanisms and predict the diffusive transport coefficient. In our framework, the transport coefficient is related to the parameters which can be computed from the potential of mean force (PMF) between permeating gas molecules and the membrane atoms. By means of Equilibrium (EMD) and Non Equilibrium (NEMD) molecular dynamics simulations, we explore the permeation of pure compounds through nanoporous graphene membranes exhibiting differentpore sizes and geometry. We also investigate the effect of thermodynamic conditions (pressure and temperature) on the transport coefficient. Simulated transport coefficients are in good agreement with the predictions of our theory over the whole range of permeation regimes. Furthermore, based on the knowledge acquired on the permeation of pure compounds, we define the concept of selectivity. By comparing the results of molecular simulations performed with gas mixtures, we show in which cases the results weobtained for pure compounds, and consequently our theoretical framework, allow us to predict the selectivity of mixtures
35
Castro, María. "Templating approaches to the synthesis of new microporous materials for gas adsorption and separation /." St Andrews, 2008. http://hdl.handle.net/10023/851.
36
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/.
Анотація:
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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Sun, Chen. "Microfluidic technology for cellular analysis and molecular biotechnology." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78742.
Анотація:
Microfluidics, the manipulation of fluids at nanoliter scale, has emerged to offer an ideal platform for biological analysis of a low number of cells. The technological advances in microfluidics have allowed both forming of valves, mixers and pumps and integrating of optic and electronic components into microfluidic devices to construct complete and functional systems. In this dissertation, I present novel microfluidic techniques and their applications in cellular probes delivery, cell separation and epigenetic study. In the first part of the dissertation, electroporation is implemented on microfluidic platform to generate uniform delivery of "exposed" nanoparticle or protein into cells. In contrast to endocytosis, electroporation is a physical method to breach cell membrane and does not involve vesicle encapsulation of delivered probes, which means these probes have exposed surface in the cytosol. Such trait enables the use of delivered nanoparticle and protein for intracellular targeting of native biomolecules. Laser-induced fluorescent microscopy was used for single particle illuminating to track single molecules in cells. Microfluidic device provide integrated platform for conducting electroporation, cell culture and imaging. In the second part, microfluidic immunomagnetic cell separation is introduced. I showed two new approaches to enhance immunomagnetic cell separation based on (1) uniquely microfabricated paramagnetic patterns inside separation channels; and (2) using combination of nonmagnetic beads and magnetic beads for selection of tumor initiating cells based on two markers of opposite preference in one step. Enhancement in cell isolation (high capture efficiency or high selection purity) is experimentally observed and the former is explained by computational model. In the final part of the dissertation, microfluidic device incorporating valves and mixers for sensitive study of chromosome conformation is presented. This device has small reaction chamber minimizing sample requirement, and allows multiple steps of biological analysis in a single chip avoiding sample loss during sample transfer. Several orders of magnitude improved detection sensitivity is achieved with our microfluidics based method. I envision all novel techniques discussed in this dissertation have great potential in application of disease prognosis, diagnosis and treatment.Ph. D.
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Yang, Ruidong. "Studies on Molecular and Ion Transport in Silicalite Membranes andApplications as Ion Separator for Redox Flow Battery." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406820402.
39
Shu, Shu. "Engineering the performance of mixed matrix membranes for gas separations." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26626.
Анотація:
Thesis (Ph.D)--Chemical Engineering, Georgia Institute of Technology, 2008.Committee Chair: Koros William; Committee Member: Hess Dennis; Committee Member: Jones Christopher; Committee Member: Meredith Carson; Committee Member: Wong CP. Part of the SMARTech Electronic Thesis and Dissertation Collection.
40
Hedeland, Ylva. "Chiral Separation of Amines by Non-Aqueous Capillary Electrophoresis using Low Molecular Weight Selectors." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Universitetsbiblioteket [distributör], 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6759.
41
Murase, Hiroki. "Flow-induced phase separation and crystallization in semidilute solutions of ultrahigh molecular weight polyethylene." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144863.
42
Ergican, Erdogan. "Molecular level separation of arsenic (V) from drinking water using cationic micelles and ultrafiltration membrane." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3210067.
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Leay, Laura. "Innovative gas separations for carbon capture : a molecular simulation study." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/innovative-gas-separations-for-carbon-capture-a-molecular-simulation-study(c6a10ed1-136c-4d2d-a3fd-6a1284b98dda).html.
Анотація:
Adverse changes in the Earth's climate are thought to be due to the output of carbon dioxide from power stations. This has led to the development of many new materials to remove CO2 from these gas streams. Polymers of intrinsic microporosity (PIMs) are a novel class of polymers that are rigid with sites of contortion. These properties result in inefficient packing and so lead to large pore volumes and high surface areas. The inclusion of Tröger’s base, a contortion site made up of two nitrogen atoms, is thought to lead to increased uptake of CO2. The combination of electrostatic interactions with strong van der Waals forces should interact favourable with the quadrupole moment of CO2.Here a molecular simulation study of a selection of these polymers is presented. The study begins by developing a quick screening method on single polymer chains. This shows that the high surface area and adsorption affinity are a result of the contorted nature of PIMs along with the inclusion of groups such as Tröger’s base.The creation of atomistic models that reproduce the space packing ability of these polymers is also explored. Methods developed for PIMs in literature are investigated along with a new method developed during this study. GCMC simulations are then used to investigate the adsorption of CO2. In this study it is seen that that these polymers possess a well percolated network of both ultramicropores and supermicropores with a significant fraction of these pores being close to the kinetic diameter of CO 2. It is posited that these pores may be the result of the inclusion of Tröger’s base. It is also shown that this produces a particularly favourable site for adsorption. The phenomenon of swelling as a result of CO2 adsorption is also investigated using a variety of methods that make use of the output from the GCMC simulations. It was found that swelling is negligible for pressures of up to 1 bar. This result is important as swelling in the polymer can lead to a reduction in selectivity and an increase in permeability, which can affect the overall material’s performance.
44
LE, THI HANH QUYEN. "MOLECULAR DESIGN OF CHELATING LIGANDS WITH HIGHLY SELECTIVE RECOGNITION AND SEPARATION FUNCTION FOR METAL IONS." 京都大学 (Kyoto University), 1997. http://hdl.handle.net/2433/202454.
45
Haldoupis, Emmanuel. "Mulitscale modeling and screening of nanoporous materials and membranes for separations." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47669.
Анотація:
The very large number of distinct structures that are known for metal-organic frameworks (MOFs) and zeolites presents both an opportunity and a challenge for identifying materials with useful properties for targeted separations. In this thesis we propose a three-stage computational methodology for addressing this issue and comprehensively screening all available nanoporous materials. We introduce efficient pore size calculations as a way of discarding large number of materials, which are unsuitable for a specific separation. Materials identified as having desired geometric characteristics can be further analyzed for their infinite dilution adsorption and diffusion properties by calculating the Henry's constants and activation energy barriers for diffusion. This enables us to calculate membrane selectivity in an unprecedented scale and use these values to generate a small set of materials for which the membrane selectivity can be calculated in detail and at finite loading using well-established computational tools. We display the results of using these methods for >500 MOFs and >160 silica zeolites for spherical adsorbates at first and for small linear molecules such as CO₂ later on. In addition we also demonstrate the size of the group of materials this procedure can be applied to, by performing these calculations, for simple adsorbate molecules, for an existing library of >250,000 hypothetical silica zeolites. Finally, efficient methods are introduced for assessing the role of framework flexibility on molecular diffusion in MOFs that do not require defining a classical forcefield for the MOF. These methods combine ab initio MD of the MOF with classical transition state theory and molecular dynamics simulations of the diffusing molecules. The effects of flexibility are shown to be large for CH₄, but not for CO₂ and other small spherical adsorbates, in ZIF-8.
46
Rungta, Meha. "Carbon molecular sieve dense film membranes for ethylene/ethane separations." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50121.
Анотація:
The current work focused on defining the material science options to fabricate novel, high performing ethylene/ethane (C₂H₄/C₂H₆) separation carbon molecular sieve (CMS) dense film membranes. Three polymer precursors: Matrimid®, 6FDA-DAM and 6FDA:BPDA-DAM were used as precursors to the CMS membranes. CMS performances were tailored by way of tuning pyrolysis conditions such as the pyrolysis temperature, heating rate, pyrolysis atmosphere etc. The CMS dense film membranes showed attractive C₂H₄/C₂H₆ separation performance far exceeding the polymeric membrane performances. Semi-quantitative diffusion size pore distributions were constructed by studying the transport performance of a range of different penetrant gases as molecular sized probes of the CMS pore structure. This, in conjunction with separation performance data, provided critical insights into the structure-performance relationships of the CMS materials. The effects of testing conditions, i.e. the testing temperature, pressure and feed composition on C₂H₄/C₂H₆ separation performance of CMS dense films were also analyzed. These studies were useful not just in predicting the membrane behavior from a practical stand-point, but also in a fundamental understanding of the nature of CMS membrane separation. The study helped clarify why CMS membranes outperform polymeric membrane performance, as well as allowed comparison between CMS derived from different precursors and processing conditions. The effects on C₂H₄/C₂H₆ separation in the presence of binary gas mixture were also assessed to get a more realistic measure of the CMS performance resulting from competition and bulk flow effects. The current work thus establishes a framework for guiding research ultimately aimed at providing a convenient, potentially scalable hollow fiber membrane formation technology for C₂H₄/C₂H₆ separation
47
Tao, Andi. "The development of computational high-throughput approaches for screening metal-organic frameworks in adsorptive separation applications." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/288485.
Анотація:
Chemical separation undoubtedly accounts for a large proportion of process industries' activities. In the past few decades, 10-15% of the world's energy consumed was resulted from separation process. Tremendous efforts have been made in separating the components of large quantities of chemical mixtures into pure or purer forms in most industrial chemists. In addition, industrial development and population growth would lead to a further increase in the global demand for energy in the future. This makes the effective and efficient energy separation process one of the most challenging tasks in engineering. Adsorptive separation using porous materials is widely used in industry today. In order for an adsorptive separation process to be efficient, the essential requirement is a selective adsorbent that possesses high surface area and preferentially adsorbs one component (or class of similar components). Metal-organic frameworks (MOFs) are promising materials for separation purposes as their diversity, due to their building block synthesis from metal clusters and organic linker, gives rise to a wide range of porous structures. Engineering of a separation process is a multi-disciplinary problem that requires a holistic approach. In particular, material selection for industrial applications in the field of MOFs is one of the most significant engineering challenges. The complexity of a screening exercise for adsorptive separations arises from the multitude of existing porous adsorbents including MOFs. There are more than 80,000 structures that have been synthesised so far, as well as the multivariate nature of that performance criteria that need to be considered when selecting or designing an optimal adsorbent for a separation process. However, it is infeasible to assess all the potential materials experimentally to identify the promising structure for a particular application. Recently, molecular simulation and mathematical modelling have seen an ever- growing contribution to the research field of MOFs. The development of these computational tools offers a unique platform for the characterisation, prediction and understanding of MOFs, complementary to experimental techniques. In the first part of this research, Monte Carlo molecular simulation and a number of advanced mathematical methods were used to investigate newly synthesised or not well-known MOFs. These computational techniques allowed not only to characterise materials with their textural properties, but also to predict and understand adsorption performances at the atomic level. Based on the insight gained from the molecular simulation, two computational high-throughput screening approaches were designed and assessed. A multi-scale approach has been proposed and used which combined high-throughput molecular simulation, data mining and advanced visualisation, process system modelling and experimental synthesis and testing. The focus here was on two main applications. On one hand, the challenging CO/N2 separation, which is critical for the petrochemical sector, where two molecules have very similar physical properties. On the other hand, the separation of chiral molecules. For CO/N2 separation, a database of 184 Cu- Cu paddle-wheels MOFs, which contains unsaturated metal centres as strong interaction sites, was extracted from CSD (Cambridge Structural Database) MOF subset for material screening. In the case of chiral separation, an efficient high-throughput approach based on calculation of Henry's constant was developed in this research. Owning to the nature of chirality, this separation of relevance to the pharmaceutical sector is crucially important. A database of 1407 homochiral MOFs was extracted, again, from CSD MOF subset for material screening of enantioselective adsorption. The results obtained in these computational high-throughput approaches allows the screening of interesting, existing structures, and would have a huge impact on making MOFs to be industrially interesting adsorbents as well as guiding the synthesis of these materials. From the many different possibilities, the ultimate interest of this work is in developing an integrated systematic study of the structure-adsorption performance relationship working with a limited library of candidate MOF structures in order to identify promising trends and materials for the specific applications mentioned above. In summary, the overall aim of this research was exploiting different computational techniques, developing novel high-throughput approaches in order to tackle important engineering challenges.
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Jennewein, Marc. "Production, radiochemical separation and chemical coupling of radioactive arsenic isotopes to synthesize radiopharmaceuticals for molecular imaging." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975967606.
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Gong, Ting. "Computational Dissection of Composite Molecular Signatures and Transcriptional Modules." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/77302.
Анотація:
This dissertation aims to develop a latent variable modeling framework with which to analyze gene expression profiling data for computational dissection of molecular signatures and transcriptional modules.
The first part of the dissertation is focused on extracting pure gene expression signals from tissue or cell mixtures. The main goal of gene expression profiling is to identify the pure signatures of different cell types (such as cancer cells, stromal cells and inflammatory cells) and estimate the concentration of each cell type. In order to accomplish this, a new blind source separation method is developed, namely, nonnegative partially independent component analysis (nPICA), for tissue heterogeneity correction (THC). The THC problem is formulated as a constrained optimization problem and solved with a learning algorithm based on geometrical and statistical principles.
The second part of the dissertation sought to identify gene modules from gene expression data to uncover important biological processes in different types of cells. A new gene clustering approach, nonnegative independent component analysis (nICA), is developed for gene module identification. The nICA approach is completed with an information-theoretic procedure for input sample selection and a novel stability analysis approach for proper dimension estimation. Experimental results showed that the gene modules identified by the nICA approach appear to be significantly enriched in functional annotations in terms of gene ontology (GO) categories.
The third part of the dissertation moves from gene module level down to DNA sequence level to identify gene regulatory programs by integrating gene expression data and protein-DNA binding data. A sparse hidden component model is first developed for this problem, taking into account a well-known biological principle, i.e., a gene is most likely regulated by a few regulators. This is followed by the development of a novel computational approach, motif-guided sparse decomposition (mSD), in order to integrate the binding information and gene expression data.
These computational approaches are primarily developed for analyzing high-throughput gene expression profiling data. Nevertheless, the proposed methods should be able to be extended to analyze other types of high-throughput data for biomedical research.Ph. D.
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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.
Анотація:
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.