Rozprawy doktorskie na temat „Natural hydrogen exploration and production”

Dans la course pour trouver des moyens de production d'hydrogène propre et bon marché, les puits d'hydrogène naturel de Bourakèbougou offrent une solution prometteuse. Non seulement l'un d'entre eux a pu être exploité avec succès pour produire de l'électricité pour le village local, mais ses vingt-quatre puits actuels offrent également une occasion unique aux géo-scientifiques de déterminer les caractéristiques des réservoirs d'hydrogène naturel, la nature des roches couvertures et les différents processus qui interviennent dans son accumulation, migration et piégeage dans les roches. Ce travail de recherche présente les études de carottage, diagraphie, géophysique et géochimie qui ont été réalisées pour mieux caractériser la nature des réservoirs d’H2 de Bourakèbougou. L’étude de la géologie régionale et de l’ensemble de la zone sur la base de l’interprétation des données de forages et des données bibliographiques a dans un premier temps été réalisée. Cela a permis de fournir une nouvelle carte géologique de la zone ainsi qu’une coupe Nord-Sud de l’ensemble du bassin. L’analyse des faciès ainsi que les données de forages ont permis de montrer qu’il existait une corrélation entre les puits stratigraphiques F1 et F2 forés en 2011 à 100 km au nord de Bourakèbougou et les puits dans la zone d’étude située plus au sud. Une structure antiforme a également été identifiée autour de Bourakèbougou. L’ensemble de ces données ont permis de valider et de fournir un modèle sédimentaire cohérent de l’ensemble de la zone. Afin d’améliorer le cadre géochronologique entre les différents événements de la zone et caractériser la succession chronologique entre les sédiments et les intrusions, des datations U/Pb ont été réalisées sur les carbonates sur Bougou-6, le puits le plus profond, et sur le puits F2. Les âges obtenus sur certains carbonates ont été largement influencés par l’intrusion de méga-sills de dolérites entre 150 et 210 Ma. Ceci est confirmé par la datation de veines issues des carbonates du réservoir principal de Bougou-6 et du puits F2. Les veines datées, notamment celle dans le réservoir principal contenant de l’H2 (Bougou-6) a donné un âge d’environ 210 Ma, ce qui correspond à la période de magmatisme dit de la Central Atlantic Magmatic Province (CAMP). Seule la datation d’un carbonate situé à 890m a donné un âge manifestement synchrone du dépôt (620 ±100 Ma). Cet âge a permis de confirmer l’âge néoprotérozoïque des sédiments et d’établir un lien avec l’événement glaciaire néoprotérozoïque survenu entre 635-710 Ma (Sturtien + Marinoen). Les analyses de carottes, imageries de puits, diagraphie, rock Eval et calcimétrie ont permis de mettre en évidence que les carbonates supérieurs dans lesquels le maximum d’H2 est accumulé correspondent majoritairement à des carbonates dolomitiques de type cap carbonates, et que l’ensemble des accumulation d’H2 se trouvaient dans des cavités karstiques (thermo-karst). Différents faciès classiques du Néoprotérozoïque ont été identifiés le long de la série, notamment des stromatolithes, des microbialites, et des diamictites. Les roches situées au-dessus du réservoir principal qui font office de couverture, principalement une dolérite, ont été caractérisées afin de savoir quel rôle elles jouaient dans le piégeage de l’H2. Non seulement les dolérites jouent un rôle important dans le piégeage par leur épaisseur cumulée, mais, plus en profondeur, la présence d’aquifères pouvait également atténuer la migration de l’H2 en le ralentissant dans sa migration vers la surface. Les analyses diagraphiques couplées aux données de production ont permis de mettre en évidence que le système hydrogène est un système dynamique qui se recharge de manière spontanée pendant la production, contrairement aux systèmes de réservoir de pétrole et de gaz. Enfin, l’analyse des données géophysiques a permis d’apporter une compréhension sur la structure globale de la zone et la signature géophysique de la phase gaz
In the race to find clean and inexpensive ways to produce hydrogen, the natural hydrogen wells of Bourakèbougou offer a promising solution. Not only has one of them been successfully exploited to generate electricity for the local village, but its current twenty-four wells also provide a unique opportunity for geoscientists to determine the key characteristics of natural hydrogen reservoirs, the nature of the cap rocks, and the various processes involved in its accumulation, migration, and trapping in the rocks. This scientific research presents core, logging, geophysical, and geochemical studies that have been conducted to better characterize the nature of Bourakèbougou's H2 reservoirs. The study of regional geology and the entire area based on drilling data interpretation and bibliographic information was initially carried out. This resulted in a new geological map of the area and a North-South cross-section of the entire basin. Facies analysis and drilling data showed a correlation between stratigraphic wells F1 and F2 drilled in 2011, 100 km north of Bourakèbougou, and the wells in the study area located further to the south. An antiform structure was also identified around Bourakèbougou. All of these data helped validate and provide a coherent sedimentary model for the entire area. To improve the geochronological framework between different events in the area and to characterize the chronological sequence between sediments and intrusions, U/Pb dating was performed on carbonates from Bougou-6, the deepest well, and well F2. The ages obtained for some carbonates were largely influenced by the intrusion of mega-sills of dolerites between 150 and 210 million years ago (Ma). This was confirmed through dating veins derived from the carbonates of the main Bougou-6 reservoir and well F2. The dated veins, especially the one in the main reservoir containing H2, provided an age of approximately 210 Ma, corresponding to the period of magmatism known as the Central Atlantic Magmatic Province (CAMP). Only the dating of a carbonate located at 890m yielded an age that was clearly synchronous with the deposition (620 ± 100 Ma). This age confirmed the Neoproterozoic age of the sediments and established a connection with the Neoproterozoic glaciation event that occurred between 635-710 Ma (Sturtian + Marinoan). Core analyses, well imaging, logging, Rock Eval, and calcimetry revealed that the upper carbonates in which the highest amount of H2 is accumulated mainly consist of dolomitic cap carbonates, and all H2 accumulations are found in karstic cavities (thermokarst). Different Neoproterozoic facies were identified along the sequence, including stromatolites, microbialites, sandstones, and diamictites. The rocks located above the main reservoir, primarily dolerite, were characterized to understand their role in trapping H2. It was found that not only do the dolerites play a significant role in trapping due to their cumulative thickness, but the presence of aquifers can also attenuate H2 migration by slowing it down in its migration towards the surface. The diagraphic analyses, coupled with production data, have revealed that the hydrogen system is a dynamic system that is spontaneously recharged in H2-rich gas at the production timescale, unlike oil and gas reservoir systems. Finally, the analysis of geophysical data provided an understanding of the overall structure of the area and the gas phase geophysical signature

The first part of this essay aims at investigating the already available and promising technologies for the biogas and bio-hydrogen production from anaerobic digestion of different organic substrates. One strives to show all the peculiarities of this complicate process, such as continuity, number of stages, moisture, biomass preservation and rate of feeding. The main outcome of this part is the awareness of the huge amount of reactor configurations, each of which suitable for a few types of substrate and circumstance. Among the most remarkable results, one may consider first of all the wet continuous stirred tank reactors (CSTR), right to face the high waste production rate in urbanised and industrialised areas. Then, there is the up-flow anaerobic sludge blanket reactor (UASB), aimed at the biomass preservation in case of highly heterogeneous feedstock, which can also be treated in a wise co-digestion scheme. On the other hand, smaller and scattered rural realities can be served by either wet low-rate digesters for homogeneous agricultural by-products (e.g. fixed-dome) or the cheap dry batch reactors for lignocellulose waste and energy crops (e.g. hybrid batch-UASB). The biological and technical aspects raised during the first chapters are later supported with bibliographic research on the important and multifarious large-scale applications the products of the anaerobic digestion may have. After the upgrading techniques, particular care was devoted to their importance as biofuels, highlighting a further and more flexible solution consisting in the reforming to syngas. Then, one shows the electricity generation and the associated heat conversion, stressing on the high potential of fuel cells (FC) as electricity converters. Last but not least, both the use as vehicle fuel and the injection into the gas pipes are considered as promising applications. The consideration of the still important issues of the bio-hydrogen management (e.g. storage and delivery) may lead to the conclusion that it would be far more challenging to implement than bio-methane, which can potentially “inherit” the assets of the similar fossil natural gas. Thanks to the gathered knowledge, one devotes a chapter to the energetic and financial study of a hybrid power system supplied by biogas and made of different pieces of equipment (natural gas thermocatalitic unit, molten carbonate fuel cell and combined-cycle gas turbine structure). A parallel analysis on a bio-methane-fed CCGT system is carried out in order to compare the two solutions. Both studies show that the apparent inconvenience of the hybrid system actually emphasises the importance of extending the computations to a broader reality, i.e. the upstream processes for the biofuel production and the environmental/social drawbacks due to fossil-derived emissions. Thanks to this “boundary widening”, one can realise the hidden benefits of the hybrid over the CCGT system.

As reserves of conventional crude oil are depleted, there is a growing need to develop unconventional oils such as heavy oil and bitumen from oil sands. In terms of recoverable oil, Canadian oil sands are considered to be the second largest oil reserves in the world. However, the upgrading of bitumen from oil sands to synthetic crude oil (SCO) requires nearly ten times more hydrogen (H₂) than the conventional crude oils. The current H₂ demand for oil sands operations is met mostly by steam reforming of natural gas. With the future expansion of oil sands operations, the demand of H₂ for oil sand operations is likely to quadruple in the next decade. As natural gas reforming involves significant carbon dioxide (CO₂) emissions, this sector is likely to be one of the largest emitters of CO₂ in Canada.

In the current H₂ plants, CO₂ emissions originate from two sources, the combustion flue gases from the steam reformer furnace and the off-gas from the process (steam reforming and water-gas shift) reactions. The objective of this study is to develop a process that captures CO₂ at minimum energy penalty in typical H₂ plants.

The approach is to look at the best operating conditions when considering the H₂ and steam production, CO₂ production and external fuel requirements. The simulation in this study incorporates the kinetics of the steam methane reforming (SMR) and the water gas shift (WGS) reactions. It also includes the integration of CO₂ capture technologies to typical H₂ plants using pressure swing adsorption (PSA) to purify the H₂ product. These typical H₂ plants are the world standard of producing H₂ and are then considered as the base case for this study. The base case is modified to account for the implementation of CO₂ capture technologies. Two capture schemes are tested in this study. The first process scheme is the integration of a monoethanolamine (MEA) CO₂ scrubbing process. The other scheme is the introduction of a cardo polyimide hollow fibre membrane capture process. Both schemes are designed to capture 80% of the CO₂ from the H₂ process at a purity of 98%.

The simulation results show that the H₂ plant with the integration of CO₂ capture has to be operated at the lowest steam to carbon (S/C) ratio, highest inlet temperature of the SMR and lowest inlet temperatures for the WGS converters to attain lowest energy penalty. H₂ plant with membrane separation technology requires higher electricity requirement. However, it produces better quality of steam than the H₂ plant with MEA-CO₂ capture process which is used to supply the electricity requirement of the process. Fuel (highvale coal) is burned to supply the additional electricity requirement. The membrane based H₂ plant requires higher additional electricity requirement for most of the operating conditions tested. However, it requires comparable energy penalty than the H₂ plant with MEA-CO₂ capture process when operated at the lowest energy operating conditions at 80% CO₂ recovery.

This thesis also investigates the sensitivity of the energy penalty as function of the percent CO₂ recovery. The break-even point is determined at a certain amount of CO₂ recovery where the amount of energy produced is equal to the amount of energy required. This point, where no additional energy is required, is approximately 73% CO₂ recovery for the MEA based capture plant and 57% CO₂ recovery for the membrane based capture plant.

The amount of CO₂ emissions at various CO₂ recoveries using the best operating conditions is also presented. The results show that MEA plant has comparable CO₂ emissions to that of the membrane plant at 80% CO₂ recovery. MEA plant is more attractive than membrane plant at lower CO₂ recoveries.

The exigent need to address climate change and its adverse effects is felt all around the world. As pioneers in tackling carbon emissions, the European Union continue to be head and shoulders above other continents by implementing policies and keeping a tab on its carbon dependence and emissions. However, being one of the largest importers of Natural Gas in the world, the EU remains dependent on a fossil fuel to meet its demands.  The aim of the research is to investigate the barriers and constraints in the EU policies and framework that affects the natural gas decarbonization and to investigate the levelized cost of hydrogen production (LCOH) that would be used to decarbonize the natural gas sector. Thus a comprehensive study, based on existing academic and scientific literature, EU policies, framework and regulations pertinent to Natural gas and a techno economic analysis of possible substitution of natural gas with Hydrogen, is performed. The motivation behind choosing hydrogen is based on various research studies that indicate the importance and ability to replace to natural gas. In addition, Portugal provides a great environment for cheap green hydrogen production and thus chosen as the main region of evaluation.  The study evaluates the current framework based on a SWOT ((Strength, Weakness, and Opportunities & Weakness) analysis, which includes a PESTEL (Political, Economic, Social, Technological, Environmental & Legal) macroeconomic factor assessment and an expert elicitation. The levelized cost of hydrogen is calculated for blue (SMR - Steam Methane Reforming with natural gas as the feedstock) and green hydrogen (Electrolyzer with electricity from grid, solar and wind sources). The costs were specific to Portuguese conditions and for the years 2020, 2030 and 2050 based on availability of data and the alignment with the National Energy and Climate Plan (NECP) and the climate action framework 2050. The sizes of Electrolyzers are based on the current Market capacities while SMR is capped at 300MW. The thesis only considers production of hydrogen. Transmission, distribution and storage of hydrogen are beyond the scope of the analysis.  Results show that the barriers are mainly related to costs competitiveness, amendments in rules/regulations, provisions of incentives, and constraints in the creation of market demand for low carbon gases. Ensuring energy security and supply while being economically feasible demands immediate amendments to the regulations and policies such as incentivizing supply, creating a demand for low carbon gases and taxation on carbon.  Considering the LCOH, the cheapest production costs continue to be dominated by blue hydrogen (1.33 € per kg of H2) in comparison to green hydrogen (4.27 and 3.68 € per kg of H2) from grid electricity and solar power respectively. The sensitivity analysis shows the importance of investments costs and the efficiency in case of electrolyzers and the carbon tax in the case of SMR. With improvements in electrolyzer technologies and increased carbon tax, the uptake of green hydrogen would be easier, ensuring a fair yet competitive gas market.
Det starka behovet av att ta itu med klimatförändringarna och deras negativa effekter är omfattande världen över. Den europeiska unionen utgör en pionjär när det gäller att såväl hantera sina koldioxidberoende och utsläpp som att implementera reglerande miljöpolitik, och framstår därmed som överlägsen andra stater och organisationer i detta hänseende. Unionen är emellertid fortfarande mycket beroende av fossilt bränsle för att uppfylla sina energibehov, och kvarstår därför som en av världens största importörer av naturgas.  Syftet med denna forskningsavhandling är att undersöka befintliga hinder och restriktioner i EU: s politiska ramverk som medför konsekvenser avkolningen av naturgas, samt att undersöka de utjämnande kostnaderna för väteproduktion (LCOH) som kan användas för att avkolna naturgassektorn. Därmed utförs en omfattande studie baserad på befintlig akademisk och vetenskaplig litteratur, EU: s politiska ramverk och stadgar som är relevanta för naturgasindustrin. Dessutom genomförs en teknisk-ekonomisk analys av eventuella ersättningar av naturgas med väte. Valet av väte som forskningsobjekt motiveras olika forskningsstudier som indikerar vikten och förmågan att ersätta till naturgas. Till sist berör studien Portugal. som tillhandahåller en lämplig miljö för billig och grön vätgasproduktion. Av denna anledning är Portugal utvalt som den viktigaste utvärderingsregionen.  Studien utvärderar det nuvarande ramverket baserat på en SWOT-analys ((Strength, Weakness, and Opportunities & Weakness), som inkluderar en PESTEL (Political, Economical, Social, Technological, Environmental och Legal) makroekonomisk faktoranalys och elicitering. Den utjömnade vätekostnaden beräknades i blått (SMR - Ångmetanreformering med naturgas som råvara) och grönt väte (elektrolyser med el från elnät, sol och vindkällor). Kostnaderna var specifika för de portugisiska förhållandena under åren 2020, 2030 och 2050 baserat på tillgänglighet av data samt anpassningen till den nationella energi- och klimatplanen (NECP) och klimatåtgärdsramen 2050. Storleken på elektrolyserar baseras på den nuvarande marknadskapaciteten medan SMR är begränsad till 300 MW. Avhandlingen tar endast hänsyn till produktionen av vätgas. Transmission, distribution och lagring av väte ligger utanför analysens räckvidd.  Resultaten visar att hindren är främst relaterade till kostnadskonkurrens, förändringar i stadgar och bestämmelser, incitament och begränsningar i formerandet av efterfrågan på koldioxidsnåla gaser på marknaden. Att säkerställa energiförsörjning och tillgång på ett ekonomiskt hållbart sätt kräver omedelbara ändringar av reglerna och politiken, såsom att stimulera utbudet, att skapa en efterfrågan på koldioxidsnåla gaser och genom att beskatta kol.  När det gäller LCOH dominerar blåväte beträffande produktionskostnaderna (1,33 € per kg H2) jämfört med grönt väte (4,27 respektive 3,68 € per kg H2) från elnät respektive solenergi. Osäkerhetsanalysen visar vikten av investeringskostnader och effektiviteten vid elektrolysörer och koldioxidskatten för SMR. Med förbättringar av elektrolys-tekniken och ökad koldioxidskatt skulle upptagningen av grön vätgas vara enklare och säkerställa en rättvis men konkurrenskraftig gasmarknad.

In light of its rapidly growing energy demand, human society has an urgent need to become much more strongly reliant on renewable and sustainable energy carriers. Molecular hydrogen made from water with solar energy could provide an ideal case. The development of inexpensive, robust and rare element free catalysts is crucial for this technology to succeed. Enzymes in nature can give us ideas about what such catalysts could look like, but for the directed adjustment of any natural or synthetic catalyst to the requirements of large scale catalysis, its capabilities and limitations need to be understood on the level of individual reaction steps. This thesis deals with kinetic and mechanistic investigations of photo- and electrocatalytic hydrogen production with natural and synthetic molecular catalysts. Photochemical hydrogen production can be achieved with both E. coli Hyd-2 [NiFe] hydrogenase and a synthetic dinuclear [FeFe] hydrogenase active site model by ruthenium polypyridyl photosensitization. The overall quantum yields are on the order of several percent. Transient UV-Vis absorption experiments reveal that these yields are strongly controlled by the competition of charge recombination reactions with catalysis. With the hydrogenase major electron losses occur at the stage of enzyme reduction by the reduced photosensitizer. In contrast, catalyst reduction is very efficient in case of the synthetic dinuclear active site model. Here, losses presumably occur at the stage of reduced catalyst intermediates. Moreover, the synthetic catalyst is prone to structural changes induced by competing ligands such as secondary amines or DMF, which lead to catalytically active, potentially mononuclear, species. Investigations of electrocatalytic hydrogen production with a mononuclear catalyst by cyclic voltammetry provide detailed kinetic and mechanistic information on the catalyst itself. By extension of existing theory, it is possible to distinguish between alternative catalytic pathways and to extract rate constants for individual steps of catalysis. The equilibrium constant for catalyst protonation can be determined, and limits can be set on both the protonation and deprotonation rate constant. Hydrogen bond formation likely involves two catalyst molecules, and even the second order rate constant characterizing hydrogen bond formation and/or release can be determined.

Afin de mieux comprendre la serpentinisation des roches mantelliques au niveau des dorsales océaniques lentes, diverses séries d’expériences ont été réalisées à 50 MPa et 250, 300 et 350 ℃ pour quantifier l’H₂ produit et clarifier les liens entre la production d’ H₂, les phases minéralogiques produites et les propriétés rédox dues à la présence d’ H₂. Les résultats, qui constituent un effort cohérent de prise en compte des paramètres et conditions rédox lors de la serpentinisation, sont les suivants : – Une nouvelle méthode expérimentale de mesure in situ de la \fH a été mise au point à 250 et 300 ℃, 50 MPa. Les deux variables exprimant la concentration d’H2 dans le fluide, \molalHydAq et \fH, ont été reliées quantitativement. Ces résultats permettent le calcul de la \fO dans les systèmes hydrothermaux océaniques à partir de la concentration en hydrogène dissout. La production d’ H₂ commence précocement, augmente rapidement et est continue au cours de la serpentinisation. – Les expériences d’interaction harzburgite-eau de mer montrent que la serpentinisation est une dissolution irréversible de l’olivine et de l’orthopyroxene et qu’elle se décompose en une succession d’étapes impliquant des assemblages de phases hors d’équilibre et métastables. – Les mécanismes de la serpentinisation et les assemblages de phases produits (en particulier les oxydes de fer) dépendent de la \fH laquelle est étroitement contrôlée par les régimes de circulation des fluides dans la croûte océanique. – La modélisation thermodynamique des fluides hydrothermaux riches en H₂ souligne le besoin de connaître précisément \yHydAq , le coefficient d’activité de \hydAq
To better understand serpentinization of mantle rocks at slow-spreading ridges, several series of experiments have been conducted at 50 MPa and 250, 300 et 350 ℃ to quantify the H₂ production associated with the serpentinization process, and to clarify the relations between the H₂ generation, the nature of product mineral phases and the redox properties of H₂ bearing hydrothermal systems. The main results of this work, which represents a significant effort toward the consideration of redox parameters and processes during serpentinisation, are the following: – A new experimental method of in situ monitoring of the \fH has been set up at 250 and 300 ℃, 50 MPa. The two variables expressing the H₂ production, \molalHydAq; aq and \fH , have been related quantitatively. Results enable the \fO of hydrothermal oceanic systems to be computed from the dissolved hydrogen concentration. H₂ production starts early, increases rapidly and is continuous in our serpentinization experiments. – Harzburgite-seawater interaction experiments show that serpentinisation is an irreversible dissolution reaction of olivine and orthopyroxene and that it consists of a sequence of discrete steps involving metastable and disequilibrium phase assemblages. – Serpentinisation mechanisms and phase assemblages (especially Fe oxides) depend on \fH, the latter being closely controlled by processes of fluid circulation in the oceanic crust. – Thermodynamic modelling of H₂ rich hydrothermal fluids stresses the need to know precisely \yHydAq, the activity coefficient of \hydAq

O hidrogênio é considerado uma fonte ideal de energia, pois sua combustão não gera contaminantes, apenas água. Dentre os processos disponíveis para produção de hidrogênio, destaca-se a decomposição catalítica do metano, pois, ao contrário do que ocorre na reforma a vapor e na oxidação parcial, nesta rota não há produção de CO. O objetivo deste trabalho é o estudo cinético e a determinação da taxa da reação de decomposição do metano sobre catalisador tipo óxido misto (Cu-Ni-Al) para obtenção de hidrogênio de alta pureza. O catalisador foi separado em quatro faixas de granulometria a fim de se determinar a influência da difusão interna à partícula na velocidade da reação, e o critério de Mears foi utilizado para avaliar o efeito da difusão externa. Os resultados obtidos mostram que, nas condições estudadas, os efeitos difusivos não influenciam significativamente a velocidade da reação. A seguir, a reação foi realizada sob diferentes temperaturas (500 a 600°C) e concentrações de metano (0,5 a 1,2 mol m-3), para determinação da equação da taxa. Observou-se que a reação é de primeira ordem, com uma energia de ativação de 50655 J mol-1. Além do hidrogênio, a reação forma carbono que se deposita na superfície do catalisador causando sua desativação. Os efeitos da regeneração do catalisador por oxidação deste carbono também foram investigados. Repetidos ciclos de reaçãoregeneração foram executados, sendo a regeneração realizada por oxidação do carbono com ar sintético ou por oxidação e redução. A oxidação foi conduzida a diferentes temperaturas (500 a 600°C) e intervalos de duração (20 a 75 min), com a reação ocorrendo em condições severas (600°C e 1,2 mol m-3 de metano). A melhor condição de regeneração, ou seja, aquela que permite um maior número de ciclos com baixa perda de atividade, foi determinada. Observou-se, também, que o carbono depositado apresenta a forma de nanotubos, os quais têm se tornado um dos campos mais ativos da nanociência e da nanotecnologia, devido a suas propriedades excepcionais. Os nanotubos de carbono formados durante a reação foram analisados, quanto a sua estrutura, por Microscopia Eletrônica de Varredura (MEV).
Hydrogen is considered the ideal source of energy, because its combustion doesn't generate pollutants, just water. The catalytic decomposition of methane stands out among the available processes for hydrogen production because, unlike steam reform and partial oxidation, in this route there is not production of CO. The objective of this work is the kinetic study and the reaction rate determination of methane catalytic decomposition over Cu-Ni-Al catalyst for pure hydrogen production. In order to determinate the limiting step, reaction was conducted using four catalyst particle size ranges and the Mears criterion was applied. The external diffusion effects and diffusion in porous catalysts step do not influence significantly the reaction rate in the studied conditions. The reaction was carried out in a thermobalance with different temperatures (500 to 600°C) and methane concentrations (0.5 to 1.2 mol m-3) to determining the reaction rate. It was observed that the reaction is of first order, with activation energy of 50655 J mol-1. The reaction also forms carbon, which is deposited on the catalyst surface causing deactivation. The carbon oxidation for catalyst regeneration was also investigated. Repeated reaction-regeneration cycles were carried out, being the regeneration composed by oxidation or by oxidation and reduction. The oxidation was carried out at different temperatures (500 to 600°C) and times (20 to 75min), with the reaction happening in severe conditions (600°C and methane concentration of 1.2 mol m-3). The best regeneration condition, that is, the condition that allows a larger number of cycles with low activity loss, it was determined. It was also observed that the deposited carbon is in the nanotubes form, which has exceptional properties. The structure of carbon nanotubes formed during the reaction was analyzed by Scanning Electron Microscopy (SEM).

Notre stratégie de développement «croissance à tout prix» a causé de nombreux problèmes environnementaux. Ainsi, la dépendance vis-à-vis des combustibles fossiles tels que le pétrole est encore plus élevée. On se doit de réduire cette dépendance. Parmi les stratégies permettant de réduire cette dépense on peut citer la production d'hydrogène, de gaz de synthèse ou d'autres produits utilisant du CO2 et/ou du CH4. L’utilisant de ces derniers est l'un des moyens prometteurs de convertir les gaz à effet de serre en produits chimiques est le procédé de reformage à sec du méthane. Ainsi, cette thèse vise à proposer de nouveaux supports utilisant de différents promoteurs pour améliorer la sélectivité et la stabilité des catalyseurs à base de nickel pour le reformage à sec du méthane ; et à analyser les performances catalytiques des catalyseurs préparés en associant les effets de température avec des caractérisations physico-chimiques telles que la mesure de surface, la diffraction des rayons X, et la désorption programmée à la température du CO2. Tout d'abord, différents promoteurs avec du nickel ont été imprégnés sur une argile naturelle ou de l’argile modifiée Fe/Cu de Tunisie. Deuxièmement, les catalyseurs dérivés de l'argile synthétique ont été préparés par une méthode de co-précipitation pour rechercher les influences de la structure sur le DRM. Enfin, les catalyseurs ayant la même composition que d'excellents catalyseurs dérivés de Ni-hydrotalcite ont été synthétisés mécaniquement par broyage planétaire pour comparer l'effet de la vitesse de rotation et de la préparation à des synthèses classiques
The development strategy of “growth-at-any-cost” has not been applied to the current development with the increased attention of various countries to environmental issues. But the dependence on fossil fuels such as petroleum will be still high in a short period of time based on the consideration of economic and social development. Thus, the focus on the production of hydrogen, syngas or other products using CO2 and/or CH4 that has attracted more attention in chemical products is the process of dry reforming of methane. Thus, this research focuses on proposing new supports loaded with different promoters to enhance the catalytic selectivity and stability of nickel-based catalysts for dry reforming of methane, and analyze the catalytic performance of prepared catalysts by associating temperature effects with multiple characterizations such as Brunauer-Emmett-Teller, X-ray diffraction, and CO2-temperature programmed desorption. First, different promoters with nickel are impregnated on natural clay or Fe/Cu-modified clay from Tunisia. Second, the synthetic clay derived catalysts are prepared by co-precipitation method to research the influences of structure on the DRM. In the end, the catalysts having the same composition as excellent Ni-hydrotalcite derived catalysts are further synthesized by ball milling to compare the effect of rotational speed and preparation

Adotando os conceitos da Nova Economia Institucional (NEI) e de sua vertente, a teoria da Economia dos Custos de Transação (ECT), apresenta-se, neste trabalho, uma discussão sobre o ambiente institucional brasileiro para o setor de exploração e produção (E&P) de petróleo e gás natural, sua regulação e caracterização. Discute-se as especificidades relativas às condições de desenvolvimento das atividades em campos de petróleo considerados maduros e/ou marginais, que constituem a maior parte das bacias brasileiras conhecidas em terra. O trabalho defende que este segmento de atividades de E&P requer um tratamento diferenciado em termos de regulação e outras políticas públicas, visando privilegiar a entrada de novos agentes e aumentar seu dinamismo no longo prazo. Contrapondo ao ambiente institucional nacional, optou-se por estudar o desenvolvimento das atividades onshore no Texas. Assim, estabelece-se comparações entre as duas realidades com relação à sua regulamentação, programas de incentivos, estrutura industrial, histórico de atividades e, principalmente, em relação à ação dos respectivos órgãos reguladores, a Agência Nacional de Petróleo, Gás Natural e Biocombustíveis (ANP), pelo Brasil, e a Texas Railroad Commission (TRC), pelo Texas. A experiência da TRC no setor petroleiro texano, cujas características presentes, por se tratar de campos produtores de petróleo maduros, possuem certa similaridade com os campos em terra no Brasil, revela uma série de direções para o aprimoramento da regulação petroleira brasileira no sentido de promover suas atividades onshore.
By Adopting the New Institutional Economics (NIE), and the theory of Transaction Cost Economics (TCE), this work discuss about the Brazilian institutional environment for oil and natural gas exploration and production (E&P), the regulation and main features. This study discusses the specificities related to the development of onshore activities on mature and/or marginal oil and gas fields. These areas are the majority on the Brazilian developed onshore segment. The Thesis sustains that such a segment of E&P activities needs a special treatment in terms of regulation and other public policies, aiming at to improving the entrance of new players in the sector and its long-term growing. For a comparative analysis, the study of the onshore activities development in Texas provides important insights to understand and criticize de Brazilian situation. The Thesis compares both realities in terms of the regulation and incentives programs, industrial structure, history of activities as well as the main role players by the respective Oil and Gas Regulator, the National Petroleum Agency (ANP) in Brazil, and the Texas Railroad Commission (TRC) in Texas. TRC’s long experience in regulating Texas’ onshore oil and gas activities, whose present situation has similarities regarding to the Brazilian onshore areas (by their maturity), reveals a series of paths to improve Brazil’s oil and gas regulation and boost its onshore activities.

Biomass has become an increasingly important renewable source of energy forenhanced energy security and reduced CO[subscript]2 emissions. Gasification is at the core of many biomass utilisation technologies for such purposes as the generation of electricity and the production of hydrogen, liquid fuels and chemicals. However, gasification faces a number of technical challenges to become a commercially feasible renewable energy technology. The most important one is the presence of tar in the gasification product gas. The ultimate purpose of this thesis was to investigate the catalytic reforming of tar using cheap catalysts as an effective means of tar destruction.In this thesis, natural ilmenite ore and novel char-supported catalysts were studied as catalysts for the steam reforming of biomass tar derived from the pyrolysis of mallee biomass in situ in two-stage fluidised-bed/fixed-bed quartz reactors. In addition to the quantification of tar conversion, the residual tar samples were also characterised with UV-fluorescence spectroscopy. Both fresh and spent catalysts were characterised with X-ray diffraction spectroscopy, FT-Raman spectroscopy and thermogravimetric analysis.The results indicate that ilmenite has activity for the reforming of tar due to its highly dispersed iron-containing species. Both the externally added steam and low concentration oxygen affect the tar reforming on ilmenite significantly. The properties of biomass affect the chemical composition of its volatiles and therefore their reforming with the ilmenite catalyst. Compared with sintering, coke deposited on ilmenite is the predominant factor for its deactivation.During the steam reforming process, the char-supported iron/nickel catalysts exhibit very high activity for the reforming of tar. In addition, NO[subscript]x precursors could be decomposed effectively on the char-supported iron catalyst during the steam reforming process. The hydrolysis of HCN and the decomposition of NH[subscript]3 on the catalyst are the key reactions for the catalytic destruction of NO[subscript]x precursors.The kinetic compensation effects demonstrate that the reaction pathways on the char-supported catalysts are similar but different from those on ilmenite. The proprieties of catalyst support could play important roles for the activities of the catalysts and the reaction pathways on the catalysts. The char support as part of the char-supported catalysts can undergo significant structural changes during the catalytic reforming of biomass volatiles.

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Este trabalho tem por objetivo identificar e avaliar a gestão dos possíveis grandes riscos (de grandes consequências), existentes no descomissionamento realizado na indústria do petróleo em ambiente offshore de uma unidade marítima fixa de exploração e produção do tipo jaqueta, localizada na Bacia de Campos, com uma lâmina d`água aproximadamente de 150 metros. Serão contemplados os grandes riscos e os cenários que se desdobram, a partir da identificação dos mesmos visando segurança operacional, ambiental e saúde ocupacional. Segundo estimativas de 2001, existiam cerca de 8.000 plataformas de petróleo offshore e 700 sondas de perfuração de poços exploratórios em mais de 500 campos em desenvolvimento, situados em mais de 100 países diferentes. Nos próximos vinte anos, se espera que mais de 6.500 plataformas e instalações venham a ser descomissionadas a um custo estimado de 20 a 40 bilhões de dólares. Entretanto, é bom lembrar que operação de descomissionamento de uma unidade marítima fixa de mesma proporção da do escopo deste trabalho, e em situação de localização idêntica, ainda não foi realizada por nenhuma operadora em nosso país.
This work aims to identify and assess potential major risks (huge consequences), existing decommissioning performed in the petroleum industry in offshore environment of a fixed unit of maritime exploration and production of kind jacket located in the Campos Basin with water depths of 150 meters. Will be addressed major risks and scenarios that unfold from their identification. According to estimates by 2001 there were about 8,000 offshore oil platforms and 700 rigs drilling exploratory wells in over 500 fields under development in more than 100 countries. In the next twenty years is expected to more than 6,500 platforms and facilities will be decommissioned at an estimated cost 29-40 billion dollars. However, it is good to remember that decommissioning operation of a maritime unit fixed proportion to the scope of this work and in the same situation and location, has not yet to be performed by any operator in our country.

abstract: Some cyanobacteria can generate hydrogen (H2) under certain physiological conditions and are considered potential agents for biohydrogen production. However, they also present low amounts of H2 production, a reaction reversal towards H2 consumption, and O2 sensitivity. Most attempts to improve H2 production have involved genetic or metabolic engineering approaches. I used a bio-prospecting approach instead to find novel strains that are naturally more apt for biohydrogen production. A set of 36, phylogenetically diverse strains isolated from terrestrial, freshwater and marine environments were probed for their potential to produce H2 from excess reductant. Two distinct patterns in H2 production were detected. Strains displaying Pattern 1, as previously known from Synechocystis sp. PCC 6803, produced H2 only temporarily, reverting to H2 consumption within a short time and after reaching only moderately high H2 concentrations. By contrast, Pattern 2 cyanobacteria, in the genera Lyngbya and Microcoleus, displayed high production rates, did not reverse the direction of the reaction and reached much higher steady-state H2 concentrations. L. aestuarii BL J, an isolate from marine intertidal mats, had the fastest production rates and reached the highest steady-state concentrations, 15-fold higher than that observed in Synechocystis sp. PCC 6803. Because all Pattern 2 strains originated in intertidal microbial mats that become anoxic in dark, it was hypothesized that their strong hydrogenogenic capacity may have evolved to aid in fermentation of the photosynthate. When forced to ferment, these cyanobacteria display similarly desirable characteristics of physiological H2 production. Again, L. aestuarii BL J had the fastest specific rates and attained the highest H2 concentrations during fermentation, which proceeded via a mixed-acid pathway to yield acetate, ethanol, lactate, H2, CO2 and pyruvate. The genome of L. aestuarii BL J was sequenced and bioinformatically compared to other cyanobacterial genomes to ascertain any potential genetic or structural basis for powerful H2 production. The association hcp exclusively in Pattern 2 strains suggests its possible role in increased H2 production. This study demonstrates the value of bioprospecting approaches to biotechnology, pointing to the strain L. aestuarii BL J as a source of useful genetic information or as a potential platform for biohydrogen production.
Dissertation/Thesis
Ph.D. Molecular and Cellular Biology 2013

碩士
國立中興大學
電機工程學系所
102
In this study, nanostructured CuO/ZnO catalyst was prepared for the hydrogen production via methanol-steam reforming (MSR). With the increased specific area from the nanostructure characteristics, it is expected that catalyst activity and chemical reaction rate can be enhanced. Moreover, the reactor size might be reduced due to the high performance of the catalyst. Using the methanol conversion resulted from conventional Cu-Zn catalyst as a comparison basis, it was found that the MSR performance depends greatly on the catalyst loading and Cu-Zn weight ratio in the catalyst in addition to the reaction temperature. With insufficient catalyst loading, it was found that catalyst activity decays rapidly during the MSR for both nanostructured and conventional Cu-Zn catalysts. The MSR performance is poor when the Cu-Zn weight ratio is low in the nanostructures catalyst. The other topic involves in this study is to carry out the preliminary study on the CO methanation using the prepared Ni/Al2O3 catalyst. With the reaction temperature of 550°C, the result indicated that the CO conversion and CH4 selectivity increased with the increase in reaction pressure which was controlled by a back pressure regulator during the experiment. Further investigation on the reaction temperature effect is required in the future.

This thesis aims to design and synthesize organic molecules to generate properties like SHG, ferroelectric and dielectric. In continuation, we have done cocrystallization studies to study the trend in between the two extremums and also evaluated the particle size as well as the particle size distribution and paved the way for the bulk production in quick time using a thermal inkjet printer. Also, we have studied and analyzed the priorities of hydrogen bond and halogen bond formation involving organic fluorine. Chapter 1 discusses the multi-component adducts of benzoic acid with differently substituted fluorobenzoic acid combinations to study the trend from solid solutions to cocrystals. The emphasis is on obtaining fundamental insights into the unusual behaviour of organic fluorine's when they are combined with benzoic acid. Chapter 2 proposes a new printing protocol to produce organic "cocrystals, eutectics, solid solutions" of interest using a thermal inkjet printer. The reduction in particle size and uniform particle size distribution have been evaluated in the multi-component adducts of API “Metronidazole”. Chapter 3 describes the preferences of Halogen Bonding and Hydrogen Bonding in selectively designed "4- halophenyl 4' -halo-2',3',5',6'-fluorobenzamides". The halogen bond's strength is varied by incorporating different halogens, and its effect on packing has been studied. Chapter 4 focuses on synthesis of N-benzylidineaniline analogues and connect them to the material applications like second harmonic generation, ferroelectric, and dielectric properties. The analysis and quantification of disorder in the nitro derivative and concomitant polymorphism in hydroxy derivative are crystallographically resolved by using single-crystal XRD technique.