Dissertations / Theses on the topic 'Hydrates'
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Nour, Sherif. "17-O NMR on Crystalline Hydrades Hydrates: Impact of Hydrogen Bonding." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32849.
Full textAlfvén, Linda, and Sorin Ignea. "Characterization of Gas hydrates." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-203043.
Full textHughes, Thomas John. "Plug Formation and Dissociation of Mixed Gas Hydrates and Methane Semi-Clathrate Hydrate Stability." Thesis, University of Canterbury. Chemical and Process Engineering, 2008. http://hdl.handle.net/10092/1579.
Full textSadeq, Dhifaf Jaafar. "Gas Hydrates Investigation: Flow Assurance for Gas Production and Effects on Hydrate-bearing Sediments." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75809.
Full textRojas, González Yenny V. "Tetrahydrofuran and natural gas hydrates formation in the presence of various inhibitors." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/2332.
Full textLe, Thi Xiu. "Experimental study on the mechanical properties and the microstructure of methane hydrate-bearing sandy sediments." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC1039.
Full textMethane hydrates (MHs), being solid ice-like compounds of methane gas and water, form naturally at high pressure and low temperature in marine or permafrost settings. They are being considered as an alternative energy resource (mainly methane hydrate-bearing sand, MHBS) but also a source of geo-hazards and climate change (MHs in both coarse and fine sediments). Knowledge of physical/mechanical properties of sediments containing MHs, depending considerably on hydrate morphologies and pore-habits, is of the importance to minimize the environmental impacts of future exploitations of methane gas from MHBS. Existing experimental works mainly focus on synthetic samples due to challenges to get cored intact methane hydrate-bearing sediment samples. Various methods have been proposed for MH formation in sandy sediments to mimic natural MHBS, but without much success. The main interests of this thesis are to investigate morphologies and pore-habits of MHs formed in synthetic MHBS at various scales and to study the effects of MHs (MH morphology and MH saturation) on the mechanical properties of MHBS.Two MH formation methods (modified from two methods existing in the literature) have been first proposed to create MHs in sandy sediments at different pore-habits. At the macroscopic scale, MH pore-habits have been predicted via comparisons between sonic wave velocities, measured and that calculated based on rock physic models. The effects of MHs formed following the two proposed methods (at different hydrate saturations) on the mechanical properties of MHBS were investigated by triaxial tests. Furthermore, Magnetic Resonance Imaging (MRI) has been used to investigate the kinetics of MH formation, MH distribution along with sample height and also MH dissociation following the depressurization method which has been considered as the most economical method for MH production from MHBS. A temperature cycle in undrained conditions was supposed to not only complete MH redistribution in pore space after the water saturation of the sample at high hydrate saturation but also make MHs distributed more homogeneously in the sample even at low hydrate saturation. Furthermore, the mechanical properties of sediments (e.g. stiffness, strength) were found higher at higher MH saturation.At the grain scale, the MH morphologies and pore habits in sandy sediments were observed by X-Ray Computed Tomography (XRCT, at Navier laboratory, Ecole des Ponts ParisTech) and Synchrotron XRCT (SXRCT, at Psiche beamline of Synchrotron SOLEIL). It has been really challenging due to not only the need of special experimental setups (needing both high pressure and low temperature controls) but also poor XRCT, SXRCT image contrast between methane hydrate and water. Specific experimental setups and scan conditions were then developed for pore-scale investigations of MH growth and MH morphologies in sandy sediments by using XRCT, SXRCT. Besides, a new method has been developed for accurate determination of volumetric fractions of a three-phase media from XRCT images. Observations (at better spatial and temporal resolution) via Optical Microscopy (in cooperation with the University of Pau) were finally used to confirm diverse MH morphologies in sandy sediments. Comparisons between observed MH morphologies, pore habits, and existing idealized models have been discussed. Methane hydrate formation in sandy sediments was supposed to be an unstable and complex process. Different types of MH morphologies and pore habits could exist in the sample. It seems vital that numerical studies on the mechanical behavior of gas hydrates in sediments, based on four idealized hydrate pore-habits, should take into account realistic hydrate morphologies and pore habits.Keywords:Methane hydrates, sandy sediments, formation, dissociation, morphologies, pore-habits, mechanical properties, XRCT, SXRCT, optical microscopy, triaxial tests, rock physic model
Jang, Jaewon. "Gas production from hydrate-bearing sediments." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41145.
Full textZugic, Minjas. "Raman spectra of clathrate hydrates." Thesis, King's College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271176.
Full textBarboux, Philippe. "Conductivite protonique dans les hydrates." Paris 6, 1987. http://www.theses.fr/1987PA066034.
Full textBarboux, Philippe. "Conductivité protonique dans les hydrates." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602594d.
Full textBarros, Parigi Rafael. "Methane hydrates: Investigating the influence of sediment type on modeled methane escape in the high latitude Northern Hemisphere." Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-192841.
Full textTownson, Iwan Meredydd. "Microbial inhibition of methane clathrate hydrates." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/41022.
Full textWang, Qian. "Structure and Thermodynamic of Halogen Hydrates." Thesis, University of California, Irvine, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1535376.
Full textSo far to our knowledge, the bromine-xenon double clathrate hydrate has not yet been completely studied. In recent research in Janda lab at UC Irvine, we obtained the thermodynamic properties and structure of bromine-xenon double clathrate by applying UV-Vis spectroscopy and determining the total vapor pressure of the clathrate. In both of the TS-I and CS-II structures, bromine could only stay in the bigger size cages, while introducing xenon as a helper gas to occupy the smaller cages. Based on this concept, we hypothesize that the bromine-xenon double clathrate has the TS-I structure type below 273K, and the CS-II structure type above this temperature. Also we calculated the enthalpy of dissociation of the TS-I bromine-xenon double clathrate as 12.305±0.170kJ/mol/K, and the CS-II clathrate as 16.574±0.143 kJ/mol/K.
Hardwick, Jack. "Simulating hydrates in shallow marine sediments." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12775/.
Full textWilson, Craig W. "High-pressure studies of ammonia hydrates." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8921.
Full textLongo, Jean Paulo Nakatu. "Electrical impedance measurements of clathrate hydrates." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1406.
Full textDentre os desafios no processo de produção de hidrocarbonetos na indústria de óleo e gás, uma área em destaque nos últimos anos é conhecida como garantia de escoamento, a qual envolve assegurar de forma contínua que os fluidos (óleo ou gás) escoem pelas tubulações que conectam o poço aos sistemas de separação na superfície. Um dos principais problemas enfrentados está ligado à deposição de hidratos de gás em tubulações, podendo estes diminuir o diâmetro útil ou até obstruir as tubulações, gerando perdas financeiras consideráveis devido a, principalmente, parada de produção. Hidratos de gás ou clatratos são estruturas cristalinas sólidas semelhantes ao gelo, normalmente formados por moléculas de água e gás em determinadas condições de pressão e temperatura. Atualmente não existe uma técnica de medição estabelecida para monitoração da formação de hidratos em tubulações. Uma técnica candidata é a medição da impedância (ou o espectro de impedância) dos fluidos, pois se trata de uma técnica simples, robusta e de baixo custo. Com o objetivo de investigar o processo de formação de hidratos de forma controlada, foram realizados e analisados diversos experimentos com três sistemas de medição diferentes operando três células de medição distintas. Um sistema totalmente comercial, um sistema misto e um sistema dedicado foram utilizados para realizar medidas de impedância do processo de formação de hidratos. Os testes foram realizados com uma substância modelo (tetrahidrofurano – THF) em mistura com água, com a qual é possível a formação de hidratos sem a necessidade do uso de uma célula pressurizada. Os dois primeiros sistemas (comercial e misto) são capazes de medir o espectro de impedância na faixa 101 Hz até 107 Hz. Já o sistema dedicado opera em frequência fixa (tipicamente 5 MHz). Os resultados mostraram-se promissores no que diz respeito à monitoração da formação de hidratos, já que diferenças consideráveis nos valores de impedância são observadas para a mistura de THF-água em estado líquido e com a presença de hidratos. Dessa maneira, o sistema desenvolvido aliado ao processamento dos dados experimentais pode ser empregado em trabalhos futuros como ferramenta simples para monitorar a formação de hidratos em tubulações.
Among the challenges in the oil and gas industry for hydrocarbon production, a featured area in recent years is known as flow assurance, which involves to guarantee the continuously stream of fluids (oil or gas) through pipelines connecting wellhead to separation systems at topside. One of the main problems is related to the deposition of gas hydrates in pipelines, since these deposits may reduce the effective pipe diameter or even clog pipelines, causing considerable financial losses mainly due to production stop. Gas hydrates or clathrates are crystalline solid ice-like structures, typically formed by water and gas molecules under certain conditions of pressure and temperature. Currently there is no established measurement technique for monitoring the hydrate formation in pipelines. One candidate technique is impedance (or impedance spectrum) measurement of fluids, since it is simple, robust and low cost. With the objective of investigating hydrate formation in a controlled environment, several experiments with three different measuring systems operating three different measuring cells have been performed and evaluated. A fully commercial, a mixed, and a dedicated measuring system were applied for obtaining impedance data of hydrates formation. The experimental tests were performed with a model substance (tetrahydrofuran - THF) in mixture with water which allows the monitoring of hydrates formation at ambient pressures (i.e. no need to use a pressurized cell). The first two systems (commercial and mixed) are able to measure the impedance spectrum in the range 10 Hz to 10 MHz. The dedicated system operates at a fixed frequency (typically 5 MHz). The results show that considerable differences in impedance values are observed for the THF-water mixture in liquid conditions and with the presence of hydrates, hence being promising in hydrates formation monitoring. In this way, the developed measurement system allied to appropriated data processing routines has the potential to be applied as simple tool to monitor hydrate formation in pipes.
Lavanant, Yves. "Etude du comportement mécanochimique des hydrates." Dijon, 1993. http://www.theses.fr/1993DIJOS062.
Full textBARRON, CECILE. "Destructuration d'amidons peu hydrates sous cisaillement." Nantes, 1999. http://www.theses.fr/1999NANT2091.
Full textKogon, Remi Albert Boris <1984>. "1H NMR Relaxation Characterization Of Hydrates." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amsdottorato.unibo.it/9773/1/1H%20NMR%20Relaxation%20Characterization%20of%20Hydrates.pdf.
Full textDe, Prunelé Alexis. "Dynamics of gas hydrate-bearing pockmarks : learnings from two cases studies from the Gulf of Guinea." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0017/document.
Full textThe present work describes the dynamics of two pockmark areas, off West Africa. The intention is to propose two different approaches to study the relationships between fluid migration and pockmarks. The first investigated area corresponds to a pockmark cluster called Preowei, located off Nigeria. Geochemical analyses and modeling were combined with seismic data to detail the hydrocarbon migration pattern at this area, with implication on both the pockmark formation and the evolution of their morphology. The proposed interpretation seeks to identify the conceptual bases of pockmark evolution over time at this area. It is argued that the cluster has been active for at least 2700 years, and it is still at the stage of hydrate formation for some pockmarks and carbonate formation for other. The second investigated pockmark, called Regab, is located off Gabon. It is a giant pockmark of 800-m diameter, characterized by an ecosystem rich in fauna, with a large variety of living species. The main core of the work done on this pockmark was focused on finding a link between the fluid chemistry and the spatial distribution of the living communities which populate it. This was achieved by combining new geochemical and bathymetric results with a well-compiled dataset from the literature
Ding, Tao. "Gas hydrates to capture and sequester CO₂." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-11102004-141404.
Full textBeltrán, Roldán Juan Guillermo. "Equilibrium and morphology studies of clathrate hydrates." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66763.
Full textL'équilibre de phases et la morphologie des hydrates de gaz ont été étudiés. Les conditions d'équilibre à quatre phases (hydrates-liquideaq-liquide-vapeur) et à trois phases (hydrates-liquideaq-vapeur) ont été déterminées pour les systèmes méthane + dioxyde de carbone + neohexane + eau et méthane + dioxyde de carbone + eau, respectivement. On a constate que la fraction molaire du dioxyde de carbone dans la phase vapeur suivait des tendances contraires dans les deux systèmes, quand a la pression d'équilibre, pour une température relativement constante. Il fut aussi observe que l'équilibre des hydrates de structure H se produit a plus basses pressions et températures que celui des hydrates de structure I quand la phase vapeur est riche en méthane ; ce phénomène étant contraire quand la phase vapeur devient riche en dioxyde de carbone a l'équilibre.Un réacteur a été conçu pour acquérir des images à haute résolution de phénomènes relatifs à la formation des hydrates à haute pression. La formation des clathrates de méthane sur des pellicules vierges a été étudiée et il a été établi que les hydrates se formaient en trois couches, chacune d'elles avec une morphologie unique. Cette différence de morphologie s'estompait à mesure que le clathrate vieillissait. Des petits grains et des surfaces lisses ont été observes dans la pellicule pour de plus grandes forces d'entraînement, alors qu'^a plus basses forces d'entraînement les grains étaient grands et les surfaces rugueuses ; le contraire s'est produit en périphérie de la pellicule. La dissociation a commence dans le périmètre de la pellicule d'hydrates et a progresse jusqu'a l'apparition de nombreuses bulles gazeuses ; a mesure que la dissociation devenait omniprésente, la pellicule d'eau reculait pour retrouver sa forme originale. Il a aussi été possible de déceler qu'une pellicule extrêmement fin
Shafiei, Rami. "Thermal imaging of tetrahydrofuran hydrates heat spread." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95244.
Full textLa recherche des hydrates de gaz a toujours été des intérêts industriels et scientifiques que leur formation poser des problèmes à l'industrie pétrolière / gaz alors ils présentent également une ressource énergétique future que les hydrates de méthane se produisent naturellement dans la croûte terrestre. Dans la présente étude, la technologie d'imagerie infrarouge est utilisée pour observer et étudier la propagation de la chaleur de la formation et la décomposition de tétrahydrofurane (THF) hydrates. En outre, en utilisant la technologie d'imagerie infrarouge, les hydrates de cristaux sont observés dans la présence du poly (N-vinylpyrrolidone) (PVP) pour étudier la croissance des cristaux en présence d'un inhibiteur de cinétique. THF a été utilisé en raison de ses conditions attainability facile qui les rendent aptes à des expériences de laboratoire.
Igboanusi, Udennaka Paul. "Properties and Production of Natural Gas Hydrates." Thesis, Imperial College London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519605.
Full textNash, Karen. "Spectroscopic studies of atmospherically relevant acid hydrates." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326422.
Full textRusso, Manuela. "Titanium oxide hydrates : optical properties and applications." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/597.
Full textCao, Zhitao 1974. "Modeling of gas hydrates from first principles." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8496.
Full textIncludes bibliographical references.
Ab initio calculations were used to determine the H20-CH4 potential energy surface (PES) accurately for use in modeling gas hydrates. Electron correlation was found to be treated accurately by the second-order Moller-Plesset method (MP2). However, a large basis set, cc-pVQZ, was found to be necessary in order to compute the binding energies to within 0.1 kcal/mol of the basis set limit. In order to sample accurately the PES, the H2O-CH4 energy of interaction was computed at 18,000 points. For these computations to be feasible, a new method was developed in which all 18,000 points were computed using MP2/6-3 1++G(2d,2p) and then corrected to near the accuracy of MP2/cc-pVQZ. The PES calculated from the six-dimensional numerical potential agrees very well with far infrared vibration-rotation-tunneling spectroscopic data and experimental second virial coefficient data at the potential minimum and larger separations. In order to study the application of different potential forms to describe phase equilibrium for Structure I gas hydrates, molecular computations were performed and results were compared. Although simple potential forms can be fit satisfactorily to experimental P-T data for ethane and cyclopropane hydrates using the van der Waals and Platteeuw model, they fail to predict accurately cage occupancies of methane hydrates. Predicted phase equilibria and cage occupancies for methane hydrates using the ab initio potential are in close agreement with experimental P-T data and measured cage occupancies. The comparison showed that only the first-principles ab initio potential is able to physically characterize both the microscopic and macroscopic behaviors of methane hydrates.
(cont.) Various sets of thermodynamic reference properties currently available in the literature were examined by applying the van der Waals and Platteeuw model to predict monovariant 3-phase equilibria for hydrate forming binary mixtures from 260 to 320 K. Experimental uncertainties were found to be large enough to cause significant changes in the prediction of dissociation pressures. The ab initio methane-water intermolecular potential was used to obtain the reference properties with significantly small deviations, and the resulting parameters are able to give the best prediction of phase equilibria over the entire temperature range.
by Zhitao Cao.
Ph.D.
Roberts, Harrison R. "Re+: Changing the Way the World Hydrates." Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/146197.
Full textDashti, Hossein. "Carbon dioxide capture using gas hydrates technology." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/75679.
Full textOignet, Jérémy. "Approche exergétique d'un procédé de réfrigération secondaire par coulis d'hydrates." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066590/document.
Full textHydrates slurries as two-phase secondary refrigerants (FFD) reduces the environmental impact of refrigeration systems because these fluids have a high energy density. Their use for cold storage could be a solution to an industrial cold distribution at various temperature levels (air-conditioning, cooling process or preservation temperature). An experimental device composed of a circulation loop and a formation tank enables to characterize the thermal-hydraulic properties of CO2 hydrates slurries in order to determine the viscosities and the convective heat transfer coefficients of hydrates slurries. With these hydraulic and thermal parameters, an energy study was carried out on the system. Within this study a numerical model was developed to evaluate the energy distribution in different experimental elements (hydrate formation tank and hydrates dissociation heat exchanger) and to determine the exergetic losses created by these components. A good agreement between the experimental data and the numerical model for the temperature evolution of the slurry has been shown. The study has confirmed that multi-phases fluids provide higher energy efficiency and less exergetic losses than one-phase fluids
Myre, Denis. "Synthesis of Carbon Dioxide Hydrates in a Slurry Bubble Column." Thesis, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/19789.
Full textBorchardt, Lars, Winfried Nickel, Mirian Casco, Irena Senkovska, Volodymyr Bon, Dirk Wallacher, Nico Grimm, Simon Krause, and Joaquín Silvestre-Albero. "Illuminating solid gas storage in confined spaces – methane hydrate formation in porous model carbons." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-221847.
Full textMartin, Ana Isabel. "Hydrate Bearing Sediments-Thermal Conductivity." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6844.
Full textAbbasi, Ghazanfer R. "Investigating the wettability effect on gas hydrate bearing sediments." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2023. https://ro.ecu.edu.au/theses/2650.
Full textRodriguez, Machine Carla Thais. "Raman spectroscopic study of CO2 capture and separation by semi-clathrate hydrates crystallization and investigation of exchange processes in hydrates." Electronic Thesis or Diss., Université de Lille (2018-2021), 2021. http://www.theses.fr/2021LILUR003.
Full textNowadays, fossil fuels are constantly burnt to fulfill the increasing human and industrial demand in energy, and as a consequence, large quantities of greenhouse gases such as carbon dioxide (CO2) are released in the atmosphere and contribute to global warming. It is therefore pressing to develop efficient post-combustion CO2 mitigation techniques that are also efficient and environment-friendly, and as such, Carbon Capture and Storage (CCS) technologies involving the Hydrate-Based Separation Process (HBSP) have attracted a lot of attention. HBSP consists in encapsulating small gas molecules (e.g. CO2, nitrogen (N2), methane (CH4)) within crystalline ice-like compounds known as clathrate hydrates or hydrates. Previous works have shown that promoters like tetra-n-butyl ammonium bromide (TBAB) considerably improves the guest-gas trapping mechanism in semi-clathrate hydrate (sc). Hence, while HBSP proves to be a suitable technique for selective CO2 capture and energy recovery, advancing the fundamental understanding of processes at play is still needed before large-scale practical applications can be routinely considered. This work aims to better comprehend CO2 separation and capture processes using sc-hydrate technology, while also exploring exchange processes in hydrates to open a perspective towards industrial applications.First, the guest distribution in the hydrate phases of CO2¬-based clathrate hydrates as a function of parameters (initial composition, p, T) is revisited and elucidated by ex-situ high-resolution Raman spectroscopy. Up to now, there is a gap in the literature regarding the discrimination of the contribution of the small and large cages in CO2-based hydrates, mainly due to the Fermi resonance effect. So far, only a single study has attempted to distinguish these contributions in CO2-clathrates, however with a questionable interpretation. One of the novelties of the present work is to revisit the vibrational properties of CO2-clathrates to identify distinct frequency shifts depending on the structural environment of CO2 molecules, thereby improving our knowledge of CO2 encapsulation mechanisms in hydrates. High-resolution Raman analysis and neutron diffraction analyses are additionally performed in CO2-based TBAB-semi-clathrates for characterization purposes.Second, the influence of two different formation protocols (quick and slow crystallization protocols, commonly used in hydrate formation) on the encapsulation mechanisms, the structure, and the selectivity of CO2+N2-TBAB compounds is investigated by in-situ Raman spectroscopy. A new dissociation point (pressure and temperature) is obtained and our results highlight that slow hydrates formation rates exert a variable performance on CO2 selectivity at temperatures far from the dissociation point, while a better performance is observed when approaching dissociation. Similarly, separation factors reach their greatest values close to the dissociation, depending however on the sc crystal structure formed. Surface morphology variation is monitored by optical microscopy and exhibits a continuous transformation with temperature, starting from a rough surface coated with polygonal or stacked shaped crystals to the formation of columnar TBAB-sc crystals near dissociation. Moreover, the influence of the formation kinetics on CO2 separation and selectivity is explored.Finally, a potential application of CO2 separation and capture by HBSP is addressed through the investigation of the exchange mechanism when exposing CO2 clathrate hydrates to N2 gas. Even though CO2 and N2 hydrates crystallize in structure sI and sII, respectively, it is a CO2-N2 mixed hydrate with a preferential occupation of the small cages by N2 molecules that forms upon N2 injection. The exchange kinetics is analyzed from the perspective of methane recovery from CO2 and CO2+N2 injections
Tabatabaei-Nejad, Seyyed Ali Reza. "Phase behaviour modelling of petroleum wax and hydrates." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/593.
Full textWestacott, Robin E. "Direct free energy calculations applied to clathrate hydrates." Thesis, University of Reading, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283787.
Full textMartinez, de Baños Maria Lourdes. "Mechanisms of formation and dissociation of cyclopentane hydrates." Thesis, Pau, 2015. http://www.theses.fr/2015PAUU3037/document.
Full textThe mechanisms of formation and dissociation of cyclopentane (CP) hydrates, which form at ambient pressure and temperatures between 0°C and 7°C, have been observed in/on/near water drops immersed in CP at scales ranging from a few nanometers to the millimeter by a variety of techniques including macrophotography and optical microscopy under various modes: bright field, differential interference contrast (DIC), fluorescence and confocal reflectance. The substrates used are either hydrophobic or hydrophilic. In a first series of experiments, a simple millifluidic method is implemented. It allows to generate, store and monitor at the same time almost a hundred of regularly-spaced water droplets of equal volume (in the µl range) separated by the guest (CP) phase in a transparent fluorinated polymeric (PFA) (hydrophobic) tubing, each droplet behaving as an independent reactor for hydrate crystallization. Insights into the ‘memory effect’ are gained by measuring the statistics of hydrate nucleation events in these reactors when chilling below 7°C the water drops. The method also allows the visualization of single-drop events such as hydrate birth and growth, and the formation of a CP-in-water emulsion upon hydrate melting, especially when an additive such as an inhibitor is added to the water. In a second series of experiments, a single water droplet in CP, either sitting or hanging from a glass substrate, is observed by microscopy under various cooling and heating sequences. Hydrate crystallization (nucleation and growth) is observed to strongly depend on subcooling at the water drop/CP interface. Two novel phenomena are visualized in detail:(i) the propagation, from the contact line of the water drop, of a hydrate halo along the glass/CP interface. (ii) hydrate crystallization in a two-dimensional CP-in-water emulsion.The two types of tools developed in this thesis open new perspectives for elucidating the mechanisms of hydrate formation and dissociation in presence of additives (promoters and inhibitors) and in the presence of a mineral substrate. Applications include hydrates in sedimentary environments, flow assurance, gas separation, etc
Hamzaoui, Jamal El. "Recherche de l'origine du comportement mécanochimique des hydrates." Dijon, 1986. http://www.theses.fr/1986DIJOS040.
Full textChoukroun, Mathieu. "Étude expérimentale et thermodynamique des hydrates sous pression." Nantes, 2007. http://www.theses.fr/2007NANT2086.
Full textIntense photochemical processes preclude the persistence of Titan’s current atmospheric methane abundance over 100 million years. Dissociation of an internal methane clathrate hydrates reservoir is a likely replenishment mechanism. As the presence of ammonia has long been suggested on Titan, high pressure – low temperature experiments have been conducted in the H2O-NH3, H2O-CH4, and H2O-NH3-CH4 systems to bring new constraints on this process. New experimental data on the melting of ices in the H2O-NH3 and H2O-NH3-CH4 systems have been acquired, which allowed developing first a thermodynamic model of ices and liquid water, and then a model of the effect of ammonia on liquid water’s activity. Experiments on the dissociation of methane clathrate hydrates in H2O-CH4 have shown its dependence on two effects : presence of nitrogen and low methane contents of the samples (below 0. 2-0. 3%) induce a decrease in the dissociation temperature of up to 15 K and 40 K, respectively. Dissociation data obtained in the ternary system H2O-NH3-CH4 suggest a significant impact of ammonia. A model of cryovolcanism applicable to Titan is proposed. It suggests that the dissociation of a superficial clathrate layer, due to interactions with cryomagmas originating from the melting of ammonia hydrates, could sustain the atmospheric methane current abundances over periods as long as 2 billion years. Episodic cryovolcanism during Titan’s history could explain the current methane amounts in its atmosphere
Picard, Vincent. "Etude du comportement thermique des oxalates hydrates d'yttrium." Dijon, 1993. http://www.theses.fr/1993DIJOS028.
Full textAraújo, Ana Catarina Fernandes. "Molecular modeling of intermolecular interactions in acid hydrates." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10947.
Full textEsta dissertação explora o mundo nanoscópico de pequenos agregados onde as pontes de hidrogénio têm um papel preponderantes usando métodos quânticos ab-initio. No capítulo introdutório, a área da química computacional é apresentada e algumas noções teóricas referentes aos métodos ab-initio, discutidas. No Capítulo 2, o desempenho de vários níveis de teoria é avaliado através do estudo de pequenos agregados de água. O capítulo 3 discute a influência dos critérios de optimização no resultado deste processo, alertando para erros comuns. No Capítulo 4, hidratos gasosos de ácido trifluoroacético (TFA), nas formas dissociada e não-dissociada, são apresentados. Um número mínimo de 4 moléculas de água é necessário para induzir a transferência do protão do TFA para a rede de moléculas de água adjacente . No entanto, 5 moléculas de água são necessárias para que o agregado dissociado se torne mais estável que o seu análogo não dissociado. O Capítulo 5 propõe um novo esquema para o cálculo ab-initio de valores de pKa. Este esquema serve-se de hidratos de ácido microsolvatado, nas formas dissociada e não dissociada, em modelo de solvatação contínuo, para calcular a energia livre de dissociação em solução. Para o conjunto de espécies testadas, incluindo 10 ácidos carboxílicos, 1 amina e 2 aminoácidos, o erro médio absoluto é 1.11, o declive experimental 1.2 e o coeficiente de correlacção 0.92, o que indica um nível de exactidão aceitável.
This dissertation concerns the study of small hydrogen bonded systems through the use of quantum mechanical ab-initio methods. In the introductory chapter, the field of computational chemistry is presented and some basic theoretical notions concerning ab-initio methods are discussed. In Chapter 2, the performance of various levels of theory is assessed through the study of small water clusters. Chapter 3 discusses the influence of optimization criteria in the outcome of the optimization procedure, warning against common pitfalls. In Chapter 4, gas-phase hydrates of trifluoroacetic acid (TFA), in both dissociated and undissociated forms, are presented. A minimum of 4 water molecules is necessary to induce proton transfer from TFA to the neighboring water molecule network. However, 5 water molecules are needed to render the dissociated hydrate more stable than its undissociated counterpart. Chapter 5 proposes a new scheme for the ab-initio calculation of pKa values. It uses microsolvated acid hydrates, in both dissociated and undissociated forms, within a continuum solvation model, to calculate the dissociation free energy in solution. For the data set used, including 10 carboxylic acids, 1 amine and 2 aminoacids, the mean usigned error (MUE) of calculated pKa values is 1.11, the experimental slope 1.2 and the correlation 0.92, which denotes a reasonable level of accuracy.
Ding, Luyi Carleton University Dissertation Chemistry. "Studies on structure and dynamics in clathrate hydrates." Ottawa, 1995.
Find full textHamzaoui, Jamal El. "Recherche de l'origine du comportement mécanochimique des hydrates." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37598189v.
Full textFranzyshen, Stephen Keith. "Acidic and Chemical Properties of Molten Salt Hydrates." W&M ScholarWorks, 1985. https://scholarworks.wm.edu/etd/1539625305.
Full textFriedman, Ross Aaron. "The dehydration of pharmaceutical hydrates under mechanical load." Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/3224.
Full textEnglish, Phillip Martin. "Structural studies of titanyl and zirconyl sulphate hydrates." Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/983.
Full textWang, Shuo. "Investigation of inhibition performance of kinetic hydrates inhibitors." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/2241.
Full textSmith, Callum Conway. "Analysis of Natural Gas Hydrates using Inert Gases." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/57085.
Full textJung, Jongwon. "Gas production from hydrate-bearing sediments:geo-mechanical implications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42841.
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