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Garcia, Edder. "CO2 adsorption from synthesis gas mixtures : understanding selectivity and capacity of new adsorbents". Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10195.
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Le développement de nouveaux adsorbants écologiques et efficaces pour la séparation du CO2 nécessite un lien quantitatif entre les propriétés des adsorbants et ses propriétés d'adsorption. Dans ce travail, nous développons une méthodologie qui prend en compte explicitement les propriétés des adsorbants, tels que le diamètre de pore, la densité, la forme de pore et la composition chimique. L'objectif est d'établir des corrélations quantitatives entre les paramètres mentionnés ci-dessus et les forces qui gouvernent la physisorption dans les milieux poreux, c'est à dire les interactions van der Waals et les interactions électrostatiques. Ainsi, les propriétés optimales des adsorbants pour la séparation du CO2 sont identifiées. En parallèle à ces études théoriques, une série d'adsorbants potentiellement intéressants pour la séparation du CO2 par PSA ont été testées expérimentalement. Une étude systématique de l'influence du centre métallique sur les séparations de mélanges CO2/CH4 et CO2/CH4/CO a été réalisée sur MOFs présentant sites coordinativement insaturés. Dans le cas des zéolithes, l'effet de la composition chimie (rapport Si / Al) sur les propriétés de séparation a été étudiés. Les capacités cycliques et des sélectivités ont été déterminées par des expériences de perçage. Les matériaux présentant un bon compromis entre la sélectivité et la capacité de travailler dans les conditions typiques de PSA ont été identifiés. Finalement, une comparaison entre la prédiction du modèle d'adsorption et les expériences a été faiteThe design of new environmentally friendly and efficient adsorbents for CO2 separation requires a quantitative link between the adsorbent properties and adsorption capabilities. In this work we develop a methodology, which explicitly takes into account the adsorbent properties, such as the pore diameter, density, pore shape and chemical composition. The objective is to establish quantitative correlations between the above-mentioned parameters and the forces that govern physisorption in porous media, i.e. van der Waals forces and electrostatic interactions. Thus, the optimal properties of the adsorbent for CO2 separation are identified. In parallel to these theoretical studies, a series of potentially interesting adsorbents for CO2 separation by PSA were tested experimentally. A systematic study of the influence of the metal center on the separations of CO2/CH4 and CO2/CH4/CO mixtures was carried out on MOFs presenting coordinatively unsaturated sites. In the case of zeolites, the effect of the framework composition (Si/Al ratio) on the separation properties was studied. The cyclic capacities and selectivities were determined by breakthrough experiments. Materials presenting a good compromise between selectivity and working capacity under typical PSA conditions were identified. Finally, a comparison between the prediction of the adsorption model and the breakthrough experiments is carried out
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Gonciaruk, Aleksandra. "Graphene and triptycene based porous materials for adsorption applications". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/graphene-and-triptycene-based-porous-materials-for-adsorption-applications(932755b9-1600-4f64-8683-00844645a58b).html.
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There were three main driving forces behind this thesis: global concern over climate change mainly due to uncontrolled carbon dioxide (CO2) emissions, the excitement over the discovery of graphene and its versatile potential, and the potential to design three-dimensional (3D) or two-dimensional (2D) structures, in our case using unique triptycene molecule. We examined two polymeric materials for CO2 adsorption and suggested simple design of disordered carbons suitable for gas adsorption studies. The approach in each task was to examine structural and adsorption properties of materials using detailed atomistic modelling employing Monte Carlo and Molecular Dynamics techniques and where possible provide experimental measurements to validate the simulations. The thesis is presented as a collection of papers and the work can be divided into three independent projects. The aim of the first project is to utilize graphene as an additive in polymer composites in order to increase separation between the polymer chains increasing available surface area. The matrix used is a polymer of intrinsic microporosity (PIM-1), which possess large surface area and narrow nano-sized ( > 2nm) pore distribution attractive for gas separation membrane applications. Adding a filler can reduce aging of the polymer, and enhance permeability across the membrane, often to the expense of loosing selectivity. Therefore, we investigated the packing of PIM-1 chains in presence of discrete 2D graphene platelets and 3D graphene-derived structures and its effect on composite structure and adsorption properties. We found that additives do not alter structural polymer properties at the molecular level preserving the same adsorption capacity and affinity. Potential permeability increase would benefit from the retention of selectivity in the material. Building on design philosophy of materials with intrinsic microporosity we continued further investigation of 3D graphene-derived structures. The idea is that highly concave molecules or polymer chains pack inefficiently creating microporous materials with sufficient surface area for gas adsorption. 3D propeller-like structures were derived from graphene arms connected through the rigid triptycene and other types of cores. The resulting structures created a large amount of micropores and showed similar CO2/CH4 selectivity to activated carbons reported in the literature. It was shown that rigid triptycene core leads to more open structures. The model was also applied to model commercially available activated carbon to predict n- perfluorohexane adsorption. The fitting to experimental structural information proved to be challenging due to trial and error nature of the approach. Nevertheless, the simple packing procedure and diverse structure design have a great potential to serve as a virtual model for porous carbons that possess pore complexity and does not require any previous experimental data to be build on. The last project concerns CO2 adsorption and selectivity over CH4 and N2 in recently reported triptycene-based polymer. The triptycene shape polymer can form a porous 2D network that can be exfoliated into free-standing sheets and potentially used as a membrane. Sheets stack in the bulk material forming anisotropic channel pores. Additionally it contains fluoro- functional groups, which are known to have a high CO2 affinity. We explored pore structure and chemistry of stacked material for gas adsorption and predicted comparable capacity and CO2 selectivity to other microporous covalent materials such as activated carbons and PIMs. The CH4/N2 selectivity was similar to currently most selective material belonging to MOF family. We showed that fluoro-group have a positive effect on CO2 affinity, however predictions are sensitive to the charges of fluorine atoms assigned by different methods.
3
Khaddour, Fadi. "Amélioration de la production de gaz des « Tight Gas Reservoirs »". Thesis, Pau, 2014. http://www.theses.fr/2014PAUU3005/document.
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La valorisation des réservoirs gaziers compacts, dits Tight Gas Reservoirs (TGR), dont les découvertes sont importantes, permettrait d’augmenter significativement les ressources mondiales d’hydrocarbures. Dans l’objectif d’améliorer la production de ces types de réservoirs, nous avons mené une étude ayant pour but de parvenir à une meilleure compréhension de la relation entre l’endommagement et les propriétés de transport des géomatériaux. L’évolution de la microstructure d’éprouvettes qui ont été soumises préalablement à des chargements dynamiques est étudiée. Une estimation de leurs perméabilités avec l’endommagement est tout d’abord présentée à l’aide d’un modèle de pores parallèles couplant un écoulement de Poiseuille avec la diffusion de Knudsen. Nous avons ensuite mené des travaux expérimentaux afin d’estimer l’évolution de la perméabilité avec l’endommagement en relation avec l’évolution de la distribution de tailles de pores. Les mesures de perméabilité sont effectuées sur des cylindres en mortier similaire aux roches tight gas, soumis à une compression uniaxiale. La caractérisation des microstructures des mortiers endommagés est réalisée par porosimétrie par intrusion de mercure. Afin d’estimer l’évolution de la perméabilité, un nouveau modèle hiérarchique aléatoire est présenté. Les comparaisons avec les données expérimentales montrent la capacité de ce modèle à estimer non seulement les perméabilités apparentes et intrinsèques mais aussi leurs évolutions sous l’effet d’un chargement introduisant une évolution de la distribution de taille de pores. Ce modèle, ainsi que le dispositif expérimental employé, ont été étendus afin d’estimer à l’avenir les perméabilités relatives de mélanges gazeux. Le dernier chapitre présente une étude de l’adsorption de méthane dans différents milieux fracturés par chocs électriques. Les résultats, utiles pour l’estimation des ressources en place, ont montré que la fracturation permet de favoriser l’extraction du gaz initialement adsorbéThe valorization of compact gas reservoirs, called tight gas reservoirs (TGR), whose discoveries are important, would significantly increase the global hydrocarbon resources. With the aim of improving the production of these types of gas, we have conducted a study to achieve a better understanding of the relationship between damage and the transport properties of geomaterials. The microstructure evolution of specimens, which were submitted beforehand to dynamic loading, has been investigated. An estimation of their permeability upon damage is first presented with the help of a bundle model of parallel capillaries coupling Poiseuille flow with Knudsen diffusion. Then, we have carried out an experimental work to estimate the permeability evolution upon damage in relation to the evolution of the pore size distribution in uniaxial compression. The measurements of permeability have been performed on mortar cylinders, designed to mimic typical tight rocks that can be found in tight gas reservoirs. Microstructural characterization of damaged mortars has been performed with the help of mercury intrusion porosimetry (MIP). To estimate the permeability evolution, a new random hierarchical model has been devised. The comparisons with the experimental data show the ability of this model to estimate not only the apparent and intrinsic permeabilities but also their evolutions under loading due to a change in the pore size distribution. This model and the experimental set up have been extended to estimate the relative permeabilities of gas mixtures in the future. The final chapter presents a study of the adsorption of methane on different porous media fractured by electrical shocks. The results, concerning the estimation of the in-place resources, have shown that fracturing can enhance the extraction of the initial amount of adsorbed gas
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TAZKRITT, SAID. "Etude du role des supports et promoteurs en reaction co/h : :(2) sur des catalyseurs a base de rhodium". Université Louis Pasteur (Strasbourg) (1971-2008), 1989. http://www.theses.fr/1989STR13102.
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Etude combinee de la reactivite, de la thermodesorption programmee et du piegeage chimique sur des catalyseurs au rhodium. Le role des promoteurs sur les changements d'activite et de selectivite est aborde. Un nouveau type d'adsorption du monoxyde de carbone peut etre observe. Pour ce nouveau mode d'adsorption, la spectrometrie infra rouge est utilisee
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Battrum, M. J. "Gas separation by adsorption". Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376289.
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Röck, Frank. "System based selectivity improvements of gas sensor arrays". Aachen Shaker, 2009. http://d-nb.info/995246033/04.
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Becer, Metin Özkan Fehime S. "Gas adsorption in volumetric system/". [s.l.]: [s.n.], 2003. http://library.iyte.edu.tr/tezler/master/kimyamuh/T000256.rar.
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Zou, Jie. "Assessment of Gas Adsorption Capacity in Shale Gas Reservoirs". Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/75387.
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A study into potential gas shales is conducted to define the controlling factors of gas adsorption and evaluate gas adsorption capacity in shale gas reservoirs. The results from high-pressure adsorption experiment show that temperature, moisture and composition affect the gas adsorption in shale. In this study, a tool is introduced to predict gas adsorption capacity. This study helps to understand the mechanism of gas adsorption and evaluate gas storage in shale gas reservoirs.
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Apolonatos, Georgia. "Gas adsorption with molecular sieve zeolites". Thesis, University of Ottawa (Canada), 1990. http://hdl.handle.net/10393/5907.
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Adsorption kinetics and equilibrium of CH$\sb4$, CO and N$\sb2$ gases were studied on various molecular sieve zeolites. Ethylyne was also tested, yet was found to be incompatible with the molecular sieves under consideration. The gas chromatographic technique was chosen as the method of studying the adsorption by which equilibrium and kinetic parameters are derived by matching the response peak to appropriate mathematical models. It was found that the synthetic zeolites (H-Mordenite, 4A zeolite, 5A zeolite) rather than naturally occurring Chabazite had a higher capacity for the adsorption of all three gases. Pure and binary gas isotherms of CH$\sb4$ and CO with molecular sieve 5A were also studied for the separation of these gases. These isotherms indicated that under the present conditions CO is preferentially adsorbed on the 5A zeolite and the adsorption capacity of the sieve increases with decreased temperature.
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Heslop, Mark J. "Binary gas adsorption in molecular sieves". Thesis, Loughborough University, 1993. https://dspace.lboro.ac.uk/2134/6861.
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This thesis is concerned with the development of sorption-effect chromatography as a rapid method for the determination of binary gas-mixture adsorption isotherms.There are many alternative non-chromatographic methods but these have inherent disadvantages the direct experimental methods require excessive equilibration times and the predictive methods require the respective pure-component isotherms and an ideal adsorbed phase. A computer simulation has shown that for an alternative chromatographic method, good results will only be obtained if both binary isotherms are close to linear. Sorption-effect chromatography is characterised by the flowrate retention time (TN) which measures the change in column inventory when a perturbation is made to the system. Along with the standard composition retention time (Tx), this extra measurement allows the gradient of each binary isotherm to be evaluated. Subsequent integration will give the respective mixture isotherm. Three gas systems (nitrogen-argon, nitrogen-helium and argon-helium) have been investigated over zeolite 5A at different temperatures. The results confirm that the adsorbed phase amounts decrease, with increasing temperature and that there are degrees of component interaction. Experimentally, thermal fluctuations in the oven will cause noise on the flowrate record making TN determination difficult. Isolation of the column from direct air flow was seen to reduce the noise level. Also, using a computer simulation model, the heat of adsorption for the above zeolite 5A systems will be easily dissipated preventing any unwanted gas temperature rises; the comparatively small column diameter was found to be a significant factor. The employment of delay lines (empty tubes) in various locations has been investigated. To directly determine TN it is necessary to used delay lines downstream of the column. Also, the chromatographic method has been extended to determine mixture isotherms by considering the change in average column pressure rather than the motion of a composition front through the column. Delay lines situated upstream of the column are able to separate these two effects, and preliminary results are satisfactory. However, the use of delay lines anywhere in the system changes the measured retention times and the theory has to be adjusted to account for this.
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Wagner, Jeffrey A. "Gas adsorption on carbon nanohorn aggregates /". Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1594488041&sid=5&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Tian, Jian Atwood J. L. "Molecular organic solids for gas adsorption and solid-gas interaction". Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6882.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Jerry L. Atwood. Vita. Includes bibliographical references.
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Röck, Frank [Verfasser]. "System-Based Selectivity Improvements of Gas Sensor Arrays / Frank Röck". Aachen : Shaker, 2009. http://d-nb.info/1156518687/34.
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Mohammad, Hasan Abid Urf Turabe Ali. "Ammonia gas adsorption on metal oxide nanoparticles". Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/13094.
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Master of ScienceDepartment of Mechanical and Nuclear Engineering
Steven J. Eckels
NanoActiveTM metal oxide particles have the ability to destructively adsorb organophosphorus compounds and chlorocarbons. These nanomaterials with unique surface morphologies are subjected to separate, low concentrations of gaseous ammonia in air. NanoActiveTM materials based on magnesium oxide have large specific surface areas and defective sites that enhance surface reactivity and consequently improved adsorptivity. In gas contaminant removal by adsorption, presence of vast specific surface area is essential for effective gas-solid interaction to take place. This is also the case in many industrial and chemical applications such as purification of gases, separation and recovery of gases, catalysis etc,. Typically carbonaceous compounds are utilized and engineered in toxic gas control systems. The purpose of this study was to compare NanoActiveTM materials with carbon based compounds in the effectivity of toxic gas adsorption at low concentrations. A test facility was designed to investigate the adsorption properties of novel materials such as adorption capacity and adsorption rate. Adsorption capacity along with adsorption kinetics is a function of properties of the adsorbent and the adsorbate as well as experimental conditions. Nanomaterials were placed on a silica matrix and tested with increasing flow rates. Electrochemical sensing devices were placed at inlet and outlet of the facility to monitor real time continuous concentration profiles. Breakthrough curves were obtained from the packed bed column experiments and saturation limits of adsorbents were measured. Adsorption rates were obtained from the breakthrough curves using modified Wheeler-Jonas equation. The NanoActiveTM materials adsorbed ammonia though to a lesser extent than the Norit® compounds. This study also included measurement of pressure drop in packed beds. This information is useful in estimating energy losses in packed bed reactors. Brauner Emmet Teller tests were carried out for the calculation of surface area, pore volume and pore size of materials. These calculations suggest surface area alone had no notable influence on adsorption capacity and adsorption rates. This lead to the conclusion that adsorption was insignificant cause of absence of functional groups with affinity towards ammonia. In brief, adsorption of ammonia is possible on NanoActiveTM materials. However functional groups such as oxy-flouro compounds should be doped with novel materials to enhance the surface interactions.
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Newby, Ruth. "Gas adsorption studies in metal-organic frameworks". Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/32287/.
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This thesis describes the synthesis of a novel highly stable metal-organic framework, NOTT-300(Cr), as well as the synthesis of three new mixed metal analogues of NOTT-300 using different compositions of aluminium and chromium. These new MOFs were used in gas sorption experiments to investigate potential selectivity and uses for gas stream separations with particular focus on CO2 and C2 hydrocarbons. The gas adsorption properties of NOTT-300(Al) for CO2 and C2 hydrocarbons are also investigated in detail. Chapter 1 – An introduction to MOFs, including their synthesis and various applications along with examples from the literature is discussed. The potential application of MOFs for difficult industrial separations is considered and a brief background on CO2 and climate change is discussed along with the current issues facing carbon capture technologies. The uses of C2 hydrocarbons and their difficult separation are also assessed. Chapter 2 – A novel Cr(III) containing analogue of NOTT-300 has been successfully synthesised (NOTT-300(Cr)) and the structure solved from the PXRD pattern. The gas adsorption properties, with specific focus on CO2 uptake and selectivity, are described and compared with those obtained for NOTT 300(Al). The CO2 adsorption in NOTT-300(Cr) was further probed using ¬in situ¬ gas loaded PXRD studies. Flow experiments were used along with IAST calculations to assess and compare the CO2/CH4 and CO2/N2 selectivity in NOTT-300(Cr) and compared with NOTT-300(Al). Although the CO2 adsorption capacity is higher for NOTT-300(Cr) than for NOTT 300(Al) (10.1 vs. 9.5 mmol g-1 at 273 K and 20 bar), the CO2 selectivity is lower due to an increased adsorption capacity for other gases such as CH4. Chapter 3 – A mixed metal NOTT-300 series containing varying amounts of Al and Cr, i.e. NOTT-300(AlCr2:1), NOTT-300(AlCr1:1) and NOTT 300(AlCr2:3), was synthesised in order to further probe the effect of the metal content on the CO2 adsorption and selectivity of this framework. Each of the materials show high CO2 adsorption capacity, however, there appears to be no specific trend in adsorption properties with respect to metal ratio. The CO2 adsorption and selectivity in NOTT 300(AlCr2:1) was further investigated using dual component adsorption isotherms and in situ gas loaded PXRD and IR studies. The three different OH groups present in the mixed metal materials form interactions of differing strength with the CO2 molecules, explaining the different adsorption properties across the series. The mixed metal series displays higher CO2 adsorption than NOTT-300(Al), but lower CO2 selectivity. When compared to NOTT 300(Cr) the CO2 adsorption of the heterometallic series is lower but the selectivities are comparable. Chapter 4 – The adsorption of C2 hydrocarbons and possible C2 separations and C2/C1 separations are investigated and compared in the NOTT-300 materials described in this thesis. All frameworks display considerably higher adsorption capacity for C2 hydrocarbons vs. CH4. However, the potential for C2 separations was more varied, with NOTT-300(AlCr1:1) showing moderate C2H4/C2H6 selectivity (2.7:1), while the calculated selectivity for NOTT 300(Cr) was negligible (1:1). NOTT-300(Al) was used in breakthrough experiments to assess the separation capability of two different hydrocarbon mixtures (C2H2/C2H4 and C2H4/C2H6).
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Xiong, Fengyang. "Desorption and Adsorption of Subsurface Shale Gas". The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1591975402482308.
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Tsige, Seyoum. "Kinetic Selectivity Effects of Binary Mixtures on Nanotube Bundles: Internal and External Adsorption". OpenSIUC, 2010. https://opensiuc.lib.siu.edu/theses/220.
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Kinetic selectivity effects that take place during the adsorption of binary mixture of gas particles in the inside and on the external surface of a single-walled carbon nanotube as well as on surface of a bundle of single-walled carbon nanotubes has been studied using a kinetic Monte Carlo technique and a lattice-gas model. We considered a homogeneous one-dimensional lattice and a heterogeneous two-dimensional lattice to represent adsorbing surfaces on a single carbon nanotube and on a bundle of carbon nanotubes respectively. We restricted adsorption/desorption only to the end sites, in the case of "pore-like" adsorption. In this work, we present effect of gas-gas interactions on the adsorption kinetics of binary mixtures on surface of carbon nanotubes. It was found that interactions caused significant change in an effective binding energy of both chemical species and as a result, change in the chemical species' adsorption rate and fractional equilibrium coverage was observed when partial pressures for the chemical species were not very low or very high. Low and high partial pressures (chemical potentials) caused long-range and short-range interactions respectively; in such cases dynamics of the system was little affected. Simulation results of adsorption kinetics of binary mixtures in pore and on the heterogeneous surface formed by two adjacent carbon nanotubes are also presented.
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Navaei, Milad. "Quartz crystal microbalance adsorption apparatus for high pressure gas adsorption measurements in nanomaterials". Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41057.
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The primary objective of this study was to develop a sensitive and cost-effective sorption system to analyze adsorption and diffusion of different gases on micro porous materials and nanotubes. A high pressure Quartz Crystal Microbalance (QCM) based adsorption apparatus for single-component gas was developed. A QCM is an acoustic-wave resonator in which the acoustic wave propagates through the crystal. Therefore, it is highly responsive to addition or removal of small amounts of mass adsorbed or deposited on the surface of the crystal. This mass sensitivity makes the QCM an ideal tool for the study of gas adsorption. The QCM-based adsorption apparatus is advantageous over the commercialized none-gravimetric and gravimetric equipment in a way that it is low-cost, highly sensitive and accurate for mass sorption applications, satisfactorily stable in a controlled environment, and can be used for thin films.
The high pressure apparatus was calibrated using Matrimid 5218, whose thermodynamic properties and adsorption parameters are known. The Matrimid was spin-coated onto a 14 mm-diameter QCM, and sorption equilibrium data for were obtained for CO₂ gas at 25, 30, 48, and 52 ºC and partial pressure range between 0 to 4 bar. In order to compare the experimental data with available literature data, the experimental data was fitted into a dual-mode adsorption model. The model results from Henry's law and a Langmuir mechanism. Comparison of the experimental adsorption isotherm of Matrimide for CO₂ gas with literature data showed reasonable agreement between the experimental and literature data.
In this study, the adsorption parameters of aluminosilicate nanotubes are observed. Aluminosilicate nanotubes are ideal materials for chemical sensing, molecule separation, and gas storage; hence, there is a need for adsorption and diffusion data on this material.
The adsorption of CO₂, N₂, and CH₄ gases on aluminosilicate nanotubes samples has been studied in the temperature range of 20° to 120° Celsius and pressure range of 0 to 8 bar. The experimental results yield the CO₂ and N₂ heat of adsorptions of -32.9 and -28.1 kJ/mol respectively.
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Diao, Rui. "Fundamental Study of Simple Gas Adsorption and Adsorption-Induced Deformation in Carbonaceous Materials". Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/56504.
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This thesis has presented a fundamental study of simple gas adsorption and adsorption-induced deformation in carbonaceous materials including both graphite and porous carbon. Monte Carlo simulation was conducted to obtain the behaviours of adsorption and adsorption-induced solid deformation that are comparable to experimental studies including the adsorption isotherm, the strain isotherm and the isosteric heat, as well as the relevant microscopic properties that facilitate the understanding of underlying mechanisms.
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Mersie, Wondimagegnehu. "Selectivity and soil behavior of chlorsulfuron". Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53563.
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Response of barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) to root-applied chlorsulfuron (2-chloro N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl) amino] carbonyl] benzenesulfonamide), a herbicide for use in small grains, was investigated. The results showed that, although wheat roots take up more chlorsulfuron than barley roots, barley was less tolerant to chlorsulfuron and chlorsulfuron was more mobile in barley. This study indicated that difference in uptake or translocation cannot explain the differential response of the two species to root-applied chlorsulfuron.
In an interaction study, significant chlorsulfuron antagonism on ryegrass (Lolium multiflorum Lam.) control by diclofop {(±)[-2-[4-(2,4-dichlorophenoxy) phenoxy) propanoic acid} was observed. Greenhouse experiments showed that the tolerance of corn (Zea mays L.) to chlorsulfuron and metsulfuron (2-[[[[(4-methoxy-6-methyl-l,3,5-triazin- -2-yl) amino] carbonyl] amino] sulfonyl] benzoic acid) was greatly increased by seed dressing with the herbicide safener NA (1,8-naphthalic anhydride).
The soil behavior of chlorsulfuron was studied in the field, greenhouse and laboratory. In the field, corn adequately tolerated soil residues present 10 months following postemergence application of chlorsulfuron at 10 to 120 g/ha. However, at the same site and rates, residues from chlorsulfuron injured corn when sampled 2 months after application. In laboratory studies chlorsulfuron was moderately adsorbed by organic matter but showed low affinity to clay. Rf values calculated from soil thin-layer chromatography closely correlated with the mobility of chlorsulfuron leached with 16.8 cm of water over a 14-day period in hand-packed soil columns. In the soil thin-layer chromatography, chlorsulfuron mobility was positively and negatively correlated with pH and organic matter, respectively. The results indicated that chlorsulfuron could be mobile in low organic matter and non-acidic soils. The relationship of chlorsulfuron phytotoxicity to soil physical and chemical properties was also evaluated. Organic matter was inversely related to chlorsulfuron phytotoxicity while no such relationship to clay content was observed. The adsorption of chlorsulfuron decreased with increasing soil pH whereas desorption was greater at alkaline pH.Ph. D.
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Bur, Christian. "Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation". Doctoral thesis, Linköpings universitet, Tillämpad sensorvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-114670.
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Gas sensitive field effect transistors based on silicon carbide, SiC-FETs, have been applied to various applications mainly in the area of exhaust and combustion monitoring. So far, these sensors have normally been operated at constant temperatures and adaptations to specific applications have been done by material and transducer platform optimization. In this thesis, the methodology of dynamic operation for selectivity enhancement is systematically developed for SiC-FETs. Temperature cycling, which is well known for metal oxide gas sensors, is transferred to SiC-FETs. Additionally, gate bias modulation is introduced increasing the performance further. The multi-dimensional sensor data are evaluated by use of pattern recognition mainly based on multivariate statistics. Different strategies for feature selection, crossvalidation, and classification methods are studied. After developing the methodology of dynamic operation, i.e., applying the virtual multi-sensor approach on SiC-FETs, the concept is validated by two different case studies under laboratory conditions: Discrimination of typical exhaust gases and quantification of nitrogen oxides in a varying background is presented. Additionally, discrimination and quantification of volatile organic compounds in the low parts-perbillion range for indoor air quality applications is demonstrated. The selectivity of SiC-FETs is enhanced further by combining temperature and gate bias cycled operation. Stability is increased by extended training.Gaskänsliga fält-effekt-transistorer baserade på halvledarmaterialet kiselkarbid (SiC-FET) har redan framgångsrikt använts för olika tillämpningar främst inom området för avgas- och förbränningsövervakning. Normalt har dessa sensorer använts vid konstant temperatur och anpassning till specifika tillämpningar har gjorts av material och sensor optimering. I denna avhandling har metoden för dynamisk modulering systematiskt utvecklats för att ökaselektiviteten av SiC-FETs. Temperatur-cykling är en välkänd metod för metalloxidsensorer och har nu tillämpats på SiC-FETs för första gången. Likaså har den pålagda gatepotentialen varierats. Mönsterigenkänningsmetoder baserade på multivariat statistik används för att utvärdera multi-dimensionella sensordata. Olika strategier för urval, korsvalidering och klassificering av okända uppgifter studeras. Efter att metodiken för dynamiska mätmetoder har beskrivits i detalj, verifieras strategin av virtuella-multisensorer genom två tester under laboratorieförhållanden. Detta visas av exemplet med separering av typiska avgaser och bestämning av koncentrationen av kväveoxider i varierande gasblandningar. Vidare har ett test genomförts där flyktiga organiska föreningar identifieras och kvantifieras för att bestämma kvaliteten på inomhusluft. Dessutom kan man öka selektiviteten av sensorerna genom att kombinera modulering av temperatur och gate-potential.
Gassensitive Feldeffekt-Transistoren basierend auf Siliziumkarbid (SiC-FET) werden überwiegend für die Abgasmessung eingesetzt. Üblicherweise werden diese Sensoren bei konstanter Temperatur betrieben. Durch die Auswahl geeigneter Materialien sowie durch die Modifikation der Sensoren können diese für verschiedene Anwendungen optimiert werden. In der vorliegenden Dissertation wird die Methodik einer dynamischen Betriebsweise zur Selektivitätssteigerung systematisch weiterentwickelt. Temperaturmodulation ist ein bewährtes Verfahren für Halbleitergassensoren, das hier auf SiC-FETs übertragen wird. In ähnlicher Weise wird auch das Gate-Potential zyklisch variiert. Mustererkennungsverfahren basierend auf multivariater Statistik werden eingesetzt, um die mehrdimensionalen Messdaten auszuwerten. Verschiedene Verfahren zur Merkmalsauswahl, Kreuzvalidierung und Klassifikation unbekannter Daten werden untersucht. Nachdem die Methodik ausführlich dargelegt wurde, wird der Ansatz des virtuellen Multisensors anhand zweier Anwendungen unter Laborbedingungen verifiziert. Dies wird am Beispiel der Konzentrationsbestimmung von Stickoxiden in variierenden Gasgemischen gezeigt. Zudem werden flüchtige organische Verbindungen im niedrigen ppb-Bereich zur Bestimmung der Innenraumluftqualität erkannt und quantifiziert. Die Selektivität kann durch die Kombination von Temperatur- und Potentialmodulation weiter gesteigert und Drifteinflüsse durch erweitertes Training kompensiert werden.
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Lang, Mason J. "CATALYTIC WASTE GASIFICATION: WATER-GAS SHIFT & SELECTIVITY OFOXIDATION FOR POLYETHYLENE". Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1560982761165342.
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Hart, J. "Separation of gases by adsorption". Thesis, University of Bath, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234617.
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Rees, G. J. "Interfacial adsorption in a gas-liquid chromatographic system". Thesis, Swansea University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638636.
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Chromatographic retention due to adsorption at the liquid/gas and liquid/solid interfaces is possible in gas-liquid chromatographic (GLC) systems, especially with polar solutes from a non-polar stationary phase. The variation of retention volumes with sample size at 60oC on several series of columns, using different support materials, was studied for di iso-propyl ether (DIPE), a polar solute, on squalane, a non-polar stationary phase. Isolation of the total adsorption contributions to retention was then performed using a semi-empirical curve fitting procedure devised by Mathiasson and Jonsson. The adsorption retentions at infinite dilution on a fully wetted porous silica support (Porasil F) was extrapolated to zero loading where the gas/liquid interfacial area (Ax) approaches the value of the support surface area (As). As was measured using the BET nitrogen adsorption method, and the sum of the support/liquid and vapour/liquid adsorption coefficients was obtained. The solid/liquid interfacial adsorption coefficient, Ks, was estimated from adsorption liquid chromatographic parameters, and was found to be small in comparison with the gas/liquid interfacial adsorption coefficient, Kx. The variation with liquid loading of the adsorption contribution to retention on two silanised supports (Chromosorb P-AW DMCS and HMDS treated Porasil F) was studied. The gas liquid interfacial area at high loading was found to be small in comparison with that of untreated Porasil F, and comparable with values obtained by other workers. At squalane loadings where a wetting transition is postulated on the silanised support, the magnitude of Ax approaches that of the unsilanised support, and helps confirm the model for the wetting transition proposed by Conder and coworkers.
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Mutasim, Z. Z. "Separation of gas mixtures by pressure swing adsorption". Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379811.
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Armstrong, Jayne. "Gas adsorption and separation properties of porous material". Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2119.
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The development of new porous materials for use in applications such as gas storage and separation processes, catalysis, catalysts supports and the removal of environmentally unfriendly species has increased rapidly over the past decade. Research into the development of these new materials has been dominated by metal organic frameworks, covalent organic frameworks, nanoporous polymers and, most recently, porous organic cage molecules. This thesis describes adsorption studies of a metal organic framework, Zn (TBAPy) and a porous tetrahedral organic cage molecule of ~ 1 nm diameter formed by the condensation reaction of 1,3,5- triformylbenzene with 1,2-ethylenediamine. The development of metal organic frameworks has traditionally involved the formation of rigid network structures, analogous to that of zeolites. More recently the focus has shifted to those of dynamic, flexible framework materials, and the response of these materials to adsorption of gases and vapours. The metal organic framework Zn (TBAPy) is based on a zinc metal centre functionalised with benzoate fragments. The initial two-dimensional structure undergoes rearrangement of the paddlewheel units to form a 3D framework, Zn (TBAPy)' upon desolvation. The ability of this 3D network to separate p-xylene and m-xylene was investigated. It was found that these isomers produced different effects on the framework, with p-xylene producing a typical Type I isotherm, whereas m-xylene induced a structural change within the material, with a much slower rate of m-xylene adsorption at higher pressures. This could potentially lead to the equilibrium separation of these two isomers by the metal organic framework Zn (TBAPy)'. The 1 nm diameter tetrahedral cage molecules formed by the condensation reaction of 1,3,5-triformylbenzene with 1,2-ethylenediamine can exist in a number of stable polymorphs, Cage 1α, Cage 1β and Cage 1γ. These polymorphs can be interconverted by exposure to certain organic vapours/solvents. The conversion of Cage 1β to Cage 1α by adsorption of probe molecules ethyl acetate, 2-butanone, diethyl ether, pentane and methanol was studied. Adsorption of ethyl acetate, 2- butanone and diethyl ether produced unusual adsorption isotherms, which included desorption of adsorbed vapour with increasing pressure during the adsorption isotherms. This desorption is attributed to the structural change from Cage 1β to Cage 1α. The unusual desorption step is not observed for methanol or pentane adsorption. The adsorption of methyl acetate was studied over a wide temperature range in order to assess the thermodynamic and kinetic characteristics of the unusual desorption step. The adsorption of dichloromethane showed the reverse transformation of Cage 1α to Cage 1β, showing that the inter conversion produces stable polymorphs. The kinetics of the structural transformation followed an Avrami model and the mechanism is an activated process. Cage 1α has voids between the cages, which are connected by very narrow constrictions that allow the kinetic molecular sieving of oxygen, carbon dioxide and nitrogen. It was found that oxygen adsorbs approximately ten times faster than nitrogen on Cage 1α, with selectivity and rate constants similar to those observed for carbon molecular sieves. The thermodynamics and kinetic results are discussed in terms of structural characteristics and diffusion into molecular cage materials. The kinetic molecular sieving is not present in the polymorph Cage 1β, which has wider pores.
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Ma, Shengqian. "Gas Adsorption Applications of Porous Metal-Organic Frameworks". Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1209411394.
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Rauch, William L. "A high selectivity gas sensor based on a semi-permeable zeolite membrane". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/20151.
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Zone, Ian Robert. "Dynamics and control of a pressure swing adsorption process". Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/762/.
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Jordi, Robin Guy. "Batch frequency response techniques in gas phase adsorption applications /". [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16290.pdf.
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Bestfather, Chris. "Upgrading landfill gas to natural gas quality: Bulk separation by pressure swing adsorption". Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28403.
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Equilibrium adsorption properties are studied on zeolites for the application of upgrading biogas from landfills. Pure adsorption isotherms of carbon dioxide (CO2) and methane (CH4) measured with a constant volume apparatus. The Henry's Law constant and the heat of adsorption for NaLSX is also determined. The adiabatic working capacity and selectivity of four adsorbents is compared. NaLSX showed the highest capacity for CO2 at elevated temperatures.
The binary equilibrium of CO2/CH4 on NaLSX is measured in a modified gas chromatograph at total mixture pressures of 1 and 3.3 atmospheres. The adsorbed phase is dominated by CO2 with a selectivity of 20 to 100 for the separation of CO2 and CH4. The increase in total pressure resulted in an increase in adsorbent capacity and a decrease in selectivity. Finally, an economic analysis relates landfill size to PSA operational costs and returns.
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Savage, Mathew. "Gas adsorption and binding properties of metal organic frameworks". Thesis, University of Nottingham, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.716474.
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This thesis describes the design, synthesis and extensive characterisation of adsorbate gas interactions of two porous Metal Organic Framework materials, constructed from the organic ligand molecule 3,3’,5,5’-biphenyl tetracarboxylic acid, and Bi111 and In111" ions respectively. Chapter 1 forms a general introduction to the global problems posed by the decrease of fossil fuel reserves, increase of pollution, and global warming, the structural and properties of MOFs, and the role they play within these fields. Particular attention is given to the determination of the nature of the binding interactions of gas molecules of interest within these materials, with the aim of designing future materials with improved properties. Chapter 2 presents the first highly porous MOF synthesised from the heavy Bi111 metal ion and investigates the density, porosity and gas adsorption properties of this material. Insight into the packing and binding of gas molecules within this material are gained by computational investigations. Chapter 3 discusses an In111 MOF, isostructural to NOTT-300 (Al), and the adsorption of the fuel gases H2 and CH4 within this material. The stepwise binding positions of these gases within this material are determined by Neutron Powder Diffraction experiments and the methane binding interactions with this material are studied computationally and by Inelastic Neutron Scattering. Chapter 4 investigates the flue gas sorption and separation properties of NOTT-300 (In) by studying the N2, CO2 and SO2 adsorption, selectivity and binding interactions of this material. The binding positions of CO2 and SO2 within NOTT-300 (In) are determined by single crystal and powder X-Ray diffraction respectively, and the framework interactions and separation properties studied by infrared spectroscopy. Interactions of N2, CO2 and SO2 with this material are further investigated by INS spectroscopy.
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Huang, Liangliang. "Computational Study of Toxic Gas Removal by Reactive Adsorption". Thesis, North Carolina State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3538542.
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Growing concerns about the environment and terrorist attacks prompt a search for effective adsorbents for removal of small molecule toxic gases, such as ammonia and hydrogen sulfide, under ambient conditions in the presence of moisture, where physical adsorption is not adequate. We use graphene oxide and CuBTC metal-organic framework as the adsorbents to explore toxic gas removal by reactive adsorption. Using ab initio density functional theory, atomistic reactive molecular dynamics and Monte Carlo simulation strategies, theoretical understanding of the underlying reaction and adsorption mechanisms of ammonia and hydrogen sulfide on graphene oxide and CuBTC metal-organic framework have been gained.
The ab initio calculation results show that ammonia and hydrogen sulfide decompose on carboxyl and epoxy functional groups and vacancy defects of graphene oxide. The existence of water molecules substantially reduces the adsorption/dissociation of ammonia or hydrogen sulfide on graphene oxide because the water molecules either form hydrogen bonds with the functional groups or adsorb more easily on the vacancy defects. Reactive molecular dynamics calculations by the ReaxFF method have been performed to propose realistic graphene oxide models for theoretical calculations. We also use reactive molecular dynamics simulation to study the thermal and hydrostatic stabilities of the CuBTC metal-organic framework and its application for ammonia removal. We predict the collapse temperature for CuBTC crystal structure and observe the partial collapse of CuBTC at lower temperatures upon ammonia adsorption. The results agree well with experiment data and provide insights on the reaction mechanism involved in such an ammonia removal process.
The research in this thesis can provide fundamental understanding, at the electronic and atomistic levels, of the roles of surface defects and functionalities for reactive adsorption of toxic gas molecules. In addition to developing experimental and theoretical algorithms to design effective adsorbents, the results are expected to find applications in air cleaning, energy storage, fuel cell technology and other scientific challenges where the separation of reactive molecules is involved.
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Mangel, Astrid. "Gas adsorption and neutron scattering studies of chromatographic supports". Thesis, University of Exeter, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239391.
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Chihara, Kazuyuki, Yosuke Kaneko, Takuya Terakado i Hisashi Mizuochi. "Diffusion in multicomponent gas adsorption on MSC5A, chromatographic study". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194787.
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Valente, Inês Alexandra Manata Antunes. "Adsorption equilibria of flue gas components on activated carbon". Master's thesis, Faculdade de Ciências e Tecnologia, 2014. http://hdl.handle.net/10362/12168.
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Chihara, Kazuyuki, Yosuke Kaneko, Takuya Terakado i Hisashi Mizuochi. "Diffusion in multicomponent gas adsorption on MSC5A, chromatographic study". Diffusion fundamentals 3 (2015) 16, S. 1-4, 2005. https://ul.qucosa.de/id/qucosa%3A14304.
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CANTI, LORENZO. "Theoretical modeling of gas adsorption in microporous aromatic polymers". Doctoral thesis, Università del Piemonte Orientale, 2016. http://hdl.handle.net/11579/81935.
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Chihara, Kazuyuki, Hidenori Nakamura i Yosuke Kaneko. "Diffusion study of multi-component gas adsorption in MSC5A by chromatographic method: Diffusion study of multi-component gas adsorption in MSC5Aby chromatographic method". Diffusion fundamentals 6 (2007) 57, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14236.
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Bur, Christian [Verfasser]. "Selectivity Enhancement of Gas Sensitive Field Effect Transistors by Dynamic Operation / Christian Bur". Aachen : Shaker, 2015. http://d-nb.info/1075437172/34.
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Liow, Daniel Ann Keng. "The modelling of diffusion controlled Pressure Wing Adsorption". Thesis, University of Surrey, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332279.
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Karra, Jagadeswarareddy. "Development of porous metal-organic frameworks for gas adsorption applications". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/45751.
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Metal-organic frameworks are a new class of porous materials that have potential applications in gas storage, separations, catalysis, sensors, non-linear optics, displays and electroluminescent devices. They are synthesized in a "building-block" approach by self-assembly of metal or metal-oxide vertices interconnected by rigid linker molecules. The highly ordered nature of MOF materials and the ability to tailor the framework's chemical functionality by modifying the organic ligands give the materials great potential for high efficiency adsorbents. In particular, MOFs that selectively adsorb CO₂ over N₂, and CH₄ are very important because they have the potential to reduce carbon emissions from coal-fired power plants and substantially diminish the cost of natural gas production. Despite their importance, MOFs that show high selective gas adsorption behavior are not so common.
Development of MOFs for gas adsorption applications has been hindered by the lack of fundamental understanding of the interactions between the host-guest systems. Knowledge of how adsorbates bind to the material, and if so where and through which interaction, as well as how different species in adsorbed mixture compete and interact with the adsorption sites is a prerequisite for considering MOFs for adsorptive gas separation applications. In this work, we seek to understand the role of structural features (such as pore sizes, open metal site, functionalized ligands, pore volume, electrostatics) on the adsorptive separation of CO₂, CO and N₂ in prototype MOFs with the help of molecular modeling studies (GCMC simulations). Our simulation results suggest that the suitable MOFs for CO₂ adsorption and separation should have small size, open metal site, or large pore volume with functionalized groups.
Some of the experimental challenges in the MOF based adsorbents for CO₂ capture include designing MOFs with smaller pores with/without open metal sites. Constructing such type of porous MOFs can lead to greater CO₂ capacities and adsorption selectivities over mixtures of CH₄ or N₂. Therefore, in the second project, we focused on design and development of small pore MOFs with/without open metal sites for adsorptive separation of carbon dioxide from binary mixtures of methane and nitrogen. We have synthesized and characterized several new MOFs (single ligand and mixed ligand MOFs) using different characterization techniques like single-crystal X-ray diffraction, powder X-ray diffraction, TGA, BET, gravimetric adsorption and examined their applicability in CO₂/N₂ and CO₂/CH₄ mixture separations. Our findings from this study suggest that further, rational development of new MOF compounds for CO₂ capture applications should focus on enriching open metal sites, increasing the pore volume, and minimizing the size of large pores.
Flue gas streams and natural gas streams containing CO₂ are often saturated by water and its presence greatly reduces the CO₂ adsorption capacities and selectivities. So, in the third project, we investigated the structural stability of the developed MOFs by measuring water vapor adsorption isotherms on them at different humid conditions to understand which type of coordination environment in MOFs can resist humid environments. The results of this study suggest that MOFs connected through nitrogen-bearing ligands show greater water stability than materials constructed solely through carboxylic acid groups.
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Krause, Simon [Verfasser]. "Negative Gas Adsorption of Flexible Metal-Organic Frameworks / Simon Krause". München : Verlag Dr. Hut, 2019. http://d-nb.info/1219178330/34.
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Chen, Linjiang. "Molecular simulations studies of gas adsorption in metal-organic frameworks". Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9366.
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Using computational tools ranging from molecular simulations – including both Monte Carlo and molecular dynamics methods – to quantum mechanical (QM) calculations (primarily at density functional theory (DFT) level), this work focuses on addressing some of the challenges faced in molecular simulations of gas adsorption in metal–organic frameworks (MOFs). This work consists of two themes: one concerns gas adsorption in MOFs with coordinatively unsaturated metal sites (cus’s), and the other one deals with predicting and understanding the breathing behaviour of the flexible MOF MIL-53(Sc). It has been shown experimentally that incorporation of cus’s – also known as “open” metal sites or unsaturated metal centres – into MOFs significantly enhances the uptake of certain gases such as CO2 and CH4. As a result of the considerably enhanced, localized guest-molecule interactions with the cus’s, it, however, remains a challenge to predict correctly adsorption isotherms and/or mechanisms in MOFs with cus’s using grand-canonical Monte Carlo (GCMC) simulations based on generic classical force fields. To address this problem, two multi-scale modelling approaches – which combine GCMC simulations with QM calculations – have been proposed in this work. The first approach is based on the direct implementation of a fluid–framework potential energy surface, calculated by a hybrid DFT/ab initio method, in the GCMC simulations. The second approach involves parameterization of ab initio force fields for GCMC simulations of gas adsorption in MOFs with cus’s. This approach focuses on the generation of accurate ab initio reference data, selection of semiempirical model potentials, and force-field fitting through a multi-objective genetic algorithm approach. The multi-scale simulation strategy not only yields adsorption isotherms in very good agreement with experimental data but also correctly captures adsorption mechanisms, including the adsorption on the cus’s, observed experimentally but absent from GCMC simulations based on generic force fields. The second challenge that this work aims to address concerns the “breathing” phenomenon of MOFs, in which the framework structure adapts its pore opening to accommodate guest molecules, for example. The breathing effect gives rise to some exceptional properties of these MOFs and hence promising applications. However, framework flexibility often poses a challenge for computational studies of such MOFs, because suitable flexible force fields for frameworks are lacking and the effort involved in developing a new one is no less a challenge. Here, an alternative to the force-field-based approach is adopted. Ab initio molecular dynamics (AIMD) simulations – which combine classical molecular dynamics simulations with electronic-structure calculations “on the fly” – have been deployed to study structural changes of the breathing MOF MIL-53(Sc) in response to changes in temperature over the range 100–623 K and adsorption of CO2 at 0–0.9 bar at 196 K. AIMD simulations employing dispersion-corrected DFT accurately simulated the experimentally observed closure of MIL-53(Sc) upon solvent removal and the transition of the empty MOF from the closed-pore phase to the very-narrow-pore phase with increasing temperature. AIMD simulations were also used to mimic the CO2 adsorption of MIL-53(Sc) in silico by allowing the MIL-53(Sc) framework to evolve freely in response to CO2 loadings corresponding to the two steps in the experimental adsorption isotherm. The resulting structures enabled the structure determination of the two CO2-containing intermediate and large-pore phases observed by experimental synchrotron X-ray diffraction studies with increasing CO2 pressure; this would not have been possible for the intermediate structure via conventional methods because of diffraction peak broadening. Furthermore, the strong and anisotropic peak broadening observed for the intermediate structure could be explained in terms of fluctuations of the framework predicted by the AIMD simulations. Fundamental insights from the molecular-level interactions further revealed the origin of the breathing of MIL-53(Sc) upon temperature variation and CO2 adsorption. Both the multi-scale simulation strategy for gas adsorption in MOFs with cus’s and the AIMD study of the stimuli-responsive breathing behaviour of MIL-53(Sc) illustrate the power and promise of combining molecular simulations with quantum mechanical calculations for the prediction and understanding of MOFs.
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Hunt, Joseph Ray. "Synthesis, characterization, and gas adsorption properties of covalent organic frameworks". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1779835631&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Paraskeva, Themis C. "Improving the performance of gas sensors for electronic noses using zeolites as selectivity modifiers". Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1445773/.
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The demanding problem of lack of selectivity in semiconducting oxide gas sensors was addressed by the combination of different technologies: shape and size selective catalysts (zeolites), chromium-titanium oxide sensing material and multi-electrode sensor arrays. Sensor devices were fabricated with additional shape and size selective catalysts (zeolites) of three different types (ZSM-5, (3 and Y) either printed over the top of the sensing material or admixed with it. The shape and size selectivity of the zeolite sensors has been demonstrated in their ability to discriminate a range of volatile organic, flavour and fragrance compounds of different molecular size and shape. To promote the selective catalytic activity of the sensors the zeolites were catalytically modified (ion exchanged) by the controlled addition of chromium catalysts. The modification increased their catalytic activity in a controlled way allowing them to selectively crack longer species into smaller ones without resulting in complete combustion of the analytes. Arrays of these sensors have been used in an electronic nose with small number of sensors and a sufficiently large variance in the response for reliable and repeatable discrimination of gases. The discrimination was as good as, and in some cases better than, that achieved using much larger sensor arrays, while also allowing additional discrimination of gases on the basis of their reactivity. Investigation of different parameters such as the chromium loading of the zeolites, the thickness of the zeolite layer, and the sensor operating temperature, allowed further improvements in the discrimination between the different tested compounds. Computational simulations of the interactions of a range of volatile organic molecules with different zeolites were performed using a commercially available software to select promising zeolite catalyst materials for the construction of new sensors and to compare computational predictions with experimental results.
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Jones, Isabel Zoe. "A surface science study of automobile exhaust gas reactions on palladium". Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298639.
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Cornelius, Chris James. "Physical and Gas Permeation Properties of a Series of Novel Hybrid Inorganic-Organic Composites Based on a Synthesized Fluorinated Polyimide". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28230.
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A series of hybrid inorganic-organic composites were fabricated from a functionalized fluorinated polyimide and tetraethoxysilane (TEOS), tetramethoxysilane, methyltrimethoxysilane (MTMOS), and phenyltrimethoxy-silane (PTMOS) employing the sol-gel process. Polyimides were synthesized from 4,4'-hexafluoroisopropylidene dianiline (6FpDA) and 4,4'-hexafluoroisopropyl-idenediphthalic anhydride (6FDA) utilizing a solution imidization technique. The hybrid materials were synthesized by in-situ sol-gel processing of the aforementioned alkoxides and a fully imidized polyimide that was functionalized with 3-aminopropyltriethoxysilane. The gas permeability, diffusivity, and selectivity were evaluated for He, O2, N2, CH4, and CO2, while the physical properties of these hybrid materials were evaluated using several analytical techniques. The results from this study revealed that gas transport and physical properties were dependent on the type of alkoxide employed in the hybrid inorganic-organic material. Gas permeability was observed to increase with increasing gas penetrant size for MTMOS and PTMOS based hybrids, while TEOS based hybrids decreased gas permeability at all compositions. In general, MTMOS based hybrid materials had the largest increases in permeability, which was attributed to an increase in free volume. The TEOS based hybrid materials had the largest decreases in permeability, while PTMOS based hybrid materials had performance in between these alkoxides. Decreased permeability for the TEOS based hybrids was attributed to the formation of lower permeable material at a particle interface and coupled with increasing tortuosity. Results of PALS studies suggested that there was an increase in free volume and pore size for MTMOS based hybrids, while both TEOS and PTMOS based hybrids had decreases in both average pore size and free volume. The temperature dependence of permeation, diffusivity, and sorption were evaluated from 35oC to 125oC. These results suggested that there was a decrease in solubility for all hybrids employed in this study. Furthermore, increases in permeability for the MTMOS based hybrids were created by increased penetrant diffusion. Physical property studies revealed that the type of inorganic material incorporated into the hybrid influences the degree of swelling, bulk density, Tg, and thermal stability. Hybrid materials were also created employing 3,5-diaminobenzoic acid (DABA) in the synthesis of modified 6FDA-6FpDA polyimides in order to evaluate how improvements in inorganic and polymer compatibility influenced the gas transport properties. From this separate study, it was found that increases in both permeability and selectivity were possible. The mechanism attributed to this simultaneous increase in permeability and selectivity was the formation of a more permeable and selective interphase at the interface of an inorganic particle and the polymer matrix. In addition to these studies, 6FDA-6FpDA polyimide molecular weights were changed from 19.3K to 35.3K to probe its role on gas transport and physical properties. These studies revealed that permeability, diffusivity, and solubility increased with increasing molecular weight, while density decreased with increasing molecular weight. These results suggest that there is an increase in free volume with increasing 6FDA-6FpDA polyimide molecular weight.Ph. D.
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Sangster, J. A. "Adsorption and electrosorption studies with activated charcoal cloth". Thesis, Liverpool John Moores University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233600.
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Uner, Murat. "Adsorption Calorimetry In Supported Catalyst Characterization: Adsorption Structure Sensitivity On Pt/y-al2o3". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605511/index.pdf.
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In this study, the structure sensitivity of hydrogen, oxygen and carbon monoxide adsorption was investigated by changing the metal particle size of Pt/Al2O3 catalysts. 2 % Pt/Al2O3 catalysts were prepared by incipient wetness methodthe particle size of the catalysts was manipulated by calcining at different temperatures. The dispersion values for the catalysts calcined in air at 683K, 773K and 823K were measured as 0.62, 0.20 and 0.03 respectively. The differential heats of adsorption of hydrogen, carbon monoxide and oxygen were measured using a SETARAM C80 Tian-Calvet calorimeter. No structure dependency was observed for hydrogen, carbon monoxide or oxygen initial heats of adsorption. The adsorbate:metal stoichiometries at saturation systematically decreased with increasing particle size. Hydrogen chemisorption sites with low and intermediate heats were lost when the particle size increased. On the other hand, oxygen and carbon monoxide initial heats and adsorption site energy distributions did not change appreciably with the metal particle size.