Dissertations / Theses on the topic 'Carbon dioxide'

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O dióxido de carbono (CO2) é um importante gás de efeito estufa. No entanto, um aumento gradual ameaça substancialmente o clima. Um dos principais desafios do planejamento ambiental é identificar um modelo que vincule todos os fatores do ciclo de carbono, ou seja, oceano – ecossistema terrestre – emissão antropogênica – atmosfera. Princípios básicos de Termodinâmica podem ser aplicados em uma modelagem estatística com bases em séries históricas para obter concentrações de CO2 na atmosfera, possibilitando a construção de cenários para uma melhor tomada de decisões. Por este motivo, foi desenvolvido no trabalho um modelo que interliga todos os fatores do ciclo de carbono, focalizando em quatro zonas térmicas ou climáticas (Boreal, Temperada, Tropical, Polar), para cálculos de armazenamento de CO2 atmosférico. Os resultados mostram que no ano 2100 se atingirá uma concentração de CO2 quatro vezes maior do que antes do período pré-industrial. A zona temperada emite quase a metade de dióxido de carbono à atmosfera na atualidade; para o ano 2100, essa emissão aumentará a quinze vezes mais que a zona tropical. A China será responsável em uma proporção de vinte quatro a onze com relação aos Estados Unidos. A estabilização das concentrações de CO2 na atmosfera será obtida quando as emissões de dióxido de carbono antropogênico tiverem uma diminuição de mais do que trinta e quatro por cento para o ano 2100 na zona temperada.
Carbon dioxide (CO2) is the most important greenhouse gas. A gradual increase on its atmospheric concentration threatens significantly the climate. One of the main challenges of environment planning is to identify a model that connects all factors that determine the carbon cycle, that is, ocean – terrestrial ecosystem – anthropogenic emissions – atmosphere. Basic thermodynamic principles can be applied in a statistical modeling with historic time series to obtain atmospheric CO2 concentration, creating the possibility of construction of scenarios that will help decision making. A model that links all carbon cycle factors was developed in this dissertation work, focusing in four thermal of climatic zones (Boreal, Temperate, Tropical, and Polar) for calculations of atmospheric CO2 storage. Results show that in 2100, the atmospheric CO2 concentration will reach a value four times higher than that of the pre-industrial period. The temperate zone already emits almost half of the carbon dioxide to the atmosphere; by 2100, this emission will increase 15 times more than that corresponding to the tropical zone. China will be responsible for emissions in a proportion of 24 to 11 in comparison to that of the United States. Stabilization of CO2 concentrations in the atmosphere will be obtained when the anthropogenic carbon dioxide emissions attain a decrease of at least 34% in 2100 in the temperate zone.

Resumo: O dióxido de carbono (CO2) é um importante gás de efeito estufa. No entanto, um aumento gradual ameaça substancialmente o clima. Um dos principais desafios do planejamento ambiental é identificar um modelo que vincule todos os fatores do ciclo de carbono, ou seja, oceano - ecossistema terrestre - emissão antropogênica - atmosfera. Princípios básicos de Termodinâmica podem ser aplicados em uma modelagem estatística com bases em séries históricas para obter concentrações de CO2 na atmosfera, possibilitando a construção de cenários para uma melhor tomada de decisões. Por este motivo, foi desenvolvido no trabalho um modelo que interliga todos os fatores do ciclo de carbono, focalizando em quatro zonas térmicas ou climáticas (Boreal, Temperada, Tropical, Polar), para cálculos de armazenamento de CO2 atmosférico. Os resultados mostram que no ano 2100 se atingirá uma concentração de CO2 quatro vezes maior do que antes do período pré-industrial. A zona temperada emite quase a metade de dióxido de carbono à atmosfera na atualidade; para o ano 2100, essa emissão aumentará a quinze vezes mais que a zona tropical. A China será responsável em uma proporção de vinte quatro a onze com relação aos Estados Unidos. A estabilização das concentrações de CO2 na atmosfera será obtida quando as emissões de dióxido de carbono antropogênico tiverem uma diminuição de mais do que trinta e quatro por cento para o ano 2100 na zona temperada.
Abstract: Carbon dioxide (CO2) is the most important greenhouse gas. A gradual increase on its atmospheric concentration threatens significantly the climate. One of the main challenges of environment planning is to identify a model that connects all factors that determine the carbon cycle, that is, ocean - terrestrial ecosystem - anthropogenic emissions - atmosphere. Basic thermodynamic principles can be applied in a statistical modeling with historic time series to obtain atmospheric CO2 concentration, creating the possibility of construction of scenarios that will help decision making. A model that links all carbon cycle factors was developed in this dissertation work, focusing in four thermal of climatic zones (Boreal, Temperate, Tropical, and Polar) for calculations of atmospheric CO2 storage. Results show that in 2100, the atmospheric CO2 concentration will reach a value four times higher than that of the pre-industrial period. The temperate zone already emits almost half of the carbon dioxide to the atmosphere; by 2100, this emission will increase 15 times more than that corresponding to the tropical zone. China will be responsible for emissions in a proportion of 24 to 11 in comparison to that of the United States. Stabilization of CO2 concentrations in the atmosphere will be obtained when the anthropogenic carbon dioxide emissions attain a decrease of at least 34% in 2100 in the temperate zone.
Orientador: João Andrade de Carvalho Junior
Coorientador: Luiz Fernando Costa Nascimento
Banca: José Antonio Perrella Balestieri
Banca: Maria Paulete Pereira Martins Jorge
Mestre

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2007.
Vita.
Includes bibliographical references.
This thesis presents work towards the development of a new catalytic C-C bond forming reaction. Alkynes and olefins insert into [(IPr)CuH]2 (IPr = N,N-bis-(2,6-diisopropylphenyl)-1,3-imidazol-2-ylidene) to give copper vinyl and copper alkyl complexes. These copper complexes insert CO2 into the Cu-C bond to form copper acrylate and copper carboxylate complexes. Acrylic and carboxylic acids can be isolated by hydrolysis. A catalytic cycle based on (IPr)copper(I) was developed. Alkynes undergo reductive carboxylation to give acrylic acids in moderate yields. Unexpected interactions between several components of the catalytic system led to a number of side reaction, most importantly between [(IPr)CuH]2 and the product silyl acrylate. The use of silylcarbonate salts to desylilate the product enhanced yield. In addition, silylcarbonates can also serve as a source of CO2.
by Gergely Sirokman.
Ph.D.

The objective of this thesis is to explore the properties of supercritical carbon dioxide (CO2). In addition, the feasibility of building a small-scale low cost system will be explained. A supercritical fluid is a fluid which exhibits properties between liquid and gas with liquid like densities and viscosities similar to a gas. Since the discovery of supercritical fluids in 1822, the use of supercritical fluids, specifically supercritical CO2, has grown in popularity. The application of supercritical CO2 has continued to grow in industrial applications since the 1970’s. Supercritical CO2’s has many beneficial properties as a “green” solvent. Supercritical CO2 as a solvent is able to be implemented in a wide range of applications from aerospace, microchip manufacturing, food production, biomedical, pharmaceutical, dry-cleaning, and many more. This thesis project included designing, building and testing a supercritical CO2 extraction apparatus that examines the use of supercritical CO2 as a solvent in the extraction process of decaffeinating coffee. Due to the fact that supercritical CO2 requires high pressure operating conditions, the apparatus design is important not only for function but also for safety. In the description portion of this paper, design considerations related to each component’s function and their specific roles in the overall system are clearly stated. Furthermore, the build process is outlined along with the overall step-by-step operation of the apparatus. Different methods of data measurements are taken while the system is running, in order to interpret the apparatus’ overall functionality. Through the exploration of this experimental data, the results were compared between different operating parameters. In order to determine the feasibility of the supercritical apparatus, the devise was tested by applying the supercritical CO2 as a solvent for the extraction of caffeine from coffee beans. Analysis of the analytical data recorded from experimental testing confirms that the apparatus produced supercritical CO2. After testing specific operating conditions, it is proven that the supercritical CO2 is able to function as a “green” solvent in this small-scale system. The experimental results from these analytical runs are compared with theoretical maximums in order to determine the efficiency of the devise. Lastly, the paper presents an overview including lessons learned from the design process and from the information gathered. Data from experimental testing is interpreted and the system design is reevaluated with suggestions for future improvements.

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Acordos internacionais sobre o aquecimento global têm identificado a urgente necessidade por uma tecnologia que capture e sequestre carbono em grande escala para reduzir as emissões de dióxido de carbono (CO2) antrópico. O sequestro e captura do CO2 por carbonatação mineral (CCSM) é uma tecnologia que tem potencial para reduzir bilhões de toneladas de CO2 por ano. O principal foco deste trabalho foi avaliar o efeito ambiental do requerimento energético relacionada à produção de carbonatos utilizando os minerais silicatos, com a finalidade de sequestrar emissões de CO2 provenientes de usinas termelétricas no Brasil. Esta pesquisa foi realizada mediante o uso do LCA - Life Cycle Assessment (NBR 14040) identificando quatro subsistemas (processos de mineração, transporte do mineral, usina termelétrica e processos de carbonatação mineral) na produção de carbonatos. Consideraram-se dois processos de carbonatação mineral: mediante o ácido clorídrico (HCl) e sais de amônia (NH4HSO4) integrados a dois tipos de usinas termelétricas (carvão e gás natural), adotando quatro cenários nos quais foram avaliados o requerimento energético, emissões de CO2 e os custos envolvidos de cada um deles, as quais utilizaram a matéria prima com maior potencial de carbonatação (mineral silicato). O presente estudo foi estruturado visando responder os seguintes assuntos: (a) O melhor mineral silicato como matéria prima para processo de carbonatação mineral, (b) A quantidade de matéria prima para a sequestro de 1 tonelada de CO2, (c) O requerimento energético do processo de carbonatação mineral para sequestrar 1 tonelada de CO2, (d) A quantidade de CO2 evitada derivada da produção de carbonatos e (e) Comparação do resultado do LCA dos processos de carbonatação mineral considerados no estudo. Os resultados amostram...
International concerns over global warming have identified the urgent need for a technology to capture and sequester carbon in large-scale to reduce anthropic carbon dioxide (CO2) emissions. Carbon dioxide capture and sequestration by mineral carbonation (CCSM) is a technology that can potentially reduce billions of tonnes of CO2 per year. The main focus of this work was to evaluate the environmental effects of energy usage related to carbonate production using mineral silicates in order to sequester CO2 emissions from Brazilian power plants. This investigation was realized using a LCA - Life Cycle Assessment (ISO14040) identified 4 subsystems (mining process, mineral transport, power plant and mineral carbonation process) on carbonate production. Two mineral carbonation processes are considered: using chloride acid (HCl) and ammonium salts (NH4HSO4) applied to two types of power plants (coal and natural gas) with the best feedstock (mineral silicate) supporting four scenarios which evaluate energy requirement, CO2 emissions and costs. This work addresses the following import issues: a) the best mineral silicate used as feedstock for mineral carbonation process, b) the amount of this mineral silicate for sequestration 1 ton CO2, c) the energy requirements of mineral carbonate process to sequester 1 ton of CO2, d) the amount of CO2 avoided derived from carbonate production and e) comparison of LCA results of the two mineral carbonation process. The LCA results shows that the best feedstock to sequester CO2 emissions from power plants in Brazil is serpentinito located in Goiâs state, the mineral carbonation process using ammonium salts is a feasible option for the less energy requirement (0,75 kW/kgCO2SEQ). The amount of CO2 avoided was 0,578 tCO2AVOIDED/tCO2SEQ, this avoided CO2 emissions can be traded as carbon... (Complete abstract click electronic access below)

Orientador: João Andrade de Carvalho
Banca: Jose Antonio Perella Balestieri
Banca: Maria Angelica Martins Costa
Banca: Turíbio Gomes Soares Neto
Banca: Christian Jeremi Coronado Rodriguez
Resumo: Acordos internacionais sobre o aquecimento global têm identificado a urgente necessidade por uma tecnologia que capture e sequestre carbono em grande escala para reduzir as emissões de dióxido de carbono (CO2) antrópico. O sequestro e captura do CO2 por carbonatação mineral (CCSM) é uma tecnologia que tem potencial para reduzir bilhões de toneladas de CO2 por ano. O principal foco deste trabalho foi avaliar o efeito ambiental do requerimento energético relacionada à produção de carbonatos utilizando os minerais silicatos, com a finalidade de sequestrar emissões de CO2 provenientes de usinas termelétricas no Brasil. Esta pesquisa foi realizada mediante o uso do LCA - Life Cycle Assessment (NBR 14040) identificando quatro subsistemas (processos de mineração, transporte do mineral, usina termelétrica e processos de carbonatação mineral) na produção de carbonatos. Consideraram-se dois processos de carbonatação mineral: mediante o ácido clorídrico (HCl) e sais de amônia (NH4HSO4) integrados a dois tipos de usinas termelétricas (carvão e gás natural), adotando quatro cenários nos quais foram avaliados o requerimento energético, emissões de CO2 e os custos envolvidos de cada um deles, as quais utilizaram a matéria prima com maior potencial de carbonatação (mineral silicato). O presente estudo foi estruturado visando responder os seguintes assuntos: (a) O melhor mineral silicato como matéria prima para processo de carbonatação mineral, (b) A quantidade de matéria prima para a sequestro de 1 tonelada de CO2, (c) O requerimento energético do processo de carbonatação mineral para sequestrar 1 tonelada de CO2, (d) A quantidade de CO2 evitada derivada da produção de carbonatos e (e) Comparação do resultado do LCA dos processos de carbonatação mineral considerados no estudo. Os resultados amostram... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: International concerns over global warming have identified the urgent need for a technology to capture and sequester carbon in large-scale to reduce anthropic carbon dioxide (CO2) emissions. Carbon dioxide capture and sequestration by mineral carbonation (CCSM) is a technology that can potentially reduce billions of tonnes of CO2 per year. The main focus of this work was to evaluate the environmental effects of energy usage related to carbonate production using mineral silicates in order to sequester CO2 emissions from Brazilian power plants. This investigation was realized using a LCA - Life Cycle Assessment (ISO14040) identified 4 subsystems (mining process, mineral transport, power plant and mineral carbonation process) on carbonate production. Two mineral carbonation processes are considered: using chloride acid (HCl) and ammonium salts (NH4HSO4) applied to two types of power plants (coal and natural gas) with the best feedstock (mineral silicate) supporting four scenarios which evaluate energy requirement, CO2 emissions and costs. This work addresses the following import issues: a) the best mineral silicate used as feedstock for mineral carbonation process, b) the amount of this mineral silicate for sequestration 1 ton CO2, c) the energy requirements of mineral carbonate process to sequester 1 ton of CO2, d) the amount of CO2 avoided derived from carbonate production and e) comparison of LCA results of the two mineral carbonation process. The LCA results shows that the best feedstock to sequester CO2 emissions from power plants in Brazil is serpentinito located in Goiâs state, the mineral carbonation process using ammonium salts is a feasible option for the less energy requirement (0,75 kW/kgCO2SEQ). The amount of CO2 avoided was 0,578 tCO2AVOIDED/tCO2SEQ, this avoided CO2 emissions can be traded as carbon... (Complete abstract click electronic access below)
Doutor

The application of carbon dioxide to wood drying processes and chemical extraction of bark was investigated. Dissolved carbon dioxide gas supersaturation in the water of green wood was utilised in decompression drying of Pinus radiata sapwood chips and in the kiln drying of collapsesusceptible Eucalyptus delegatensis heartwood. The transport properties and solubilities of dissolved carbon dioxide gas in green wood that form the basis of such treatments were studied in Nothofagus fusca heartwood. Supercritical carbon dioxide and carbon dioxide/methanol were utilised to extract resin acid, fatty acids, and sterols from Pinus radiata bark. Non-steady state desorption of dissolved carbon dioxide gas from wood samples saturated with carbon dioxide gas under pressure was used to measure transverse diffusion coefficients of dissolved carbon dioxide gas in green Nothofagus fusca heartwood. The activation energy of dissolved carbon dioxide gas diffusion in green N. fusca heartwood was higher than the activation energy of dissolved carbon dioxide gas diffusion in water, suggesting the presence of a reaction mechanism between the dissolved carbon dioxide gas molecules and the cell wall constituents. Initial carbon dioxide gas loss after decompression is both rapid and substantial. This is due to mass flow of carbon dioxide gas bubbles from surface vessels and longitudinal diffusion, principally from the end grain. In long wood samples the majority of carbon dioxide gas is lost by transverse diffusion. A bimodal diffusion equation is proposed for modelling carbon dioxide gas absorption and desorption by longitudinal and transverse diffusion. Carbon dioxide gas solubilities in the water of green wood were similar to published values of solubilities in pure water. Carbon dioxide gas bubble nucleation in supersaturated aqueous solutions on decompression in Pinus radiata sapwood chips, partially saturated with carbon dioxide gas under pressure, was effective in removing a significant proportion of the water. The volume of gas bubbles formed was found to be an important criterion for water loss at high carbon dioxide gas solubilities. Water loss increased with gas pressure and absorption time. Large variations in water loss occurred with temperature at low gas pressure. Water loss was found to be more effective with repeated cycles of decompression drying. At low gas solubilities in water the volume of air in the wood became an important criterion for water loss. Compression and expansion of air bubbles was thought to be the main mode of water loss at low gas solubilities along with expansion of compressed gas that had moved behind the wet line through adjacent dry tracheids. The energy efficiency of decompression drying was far lower than that of compression drying with hydraulically driven platens. Drying collapse in Eucalyptus delegatensis heartwood was unaffected by carbon dioxide gas supersaturation in the sap of green wood, saturated under pressure at a range of gas solubilities and dried at different temperatures. It appears that carbon dioxide gas bubble nucleation does not occur within the water-saturated cells of impermeable heartwood. Drying temperature did have a significant effect on drying collapse, however, the response varied greatly with the wood source. Significant drying collapse and basic density variation occurred among the regions Nelson and Southland, among trees within the regions, and among height classes within the trees. The differences in drying collapse between the two regions was attributed to regional differences in the pattern of inter- and intra-incremental basic density variation, caused by strong environmental control of these wood properties. The significant variation of drying collapse among trees within regions suggests some genetic control of drying collapse. Pinus radiata bark was extracted using a once-through flow of supercritical carbon dioxide at a temperature of 50°C and pressures from 10 to 30 MPa. Extraction was also performed with supercritical carbon dioxide containing 4.3% methanol as a co-solvent at 30 MPa. Extract yields increased with pressure. HPLC analysis using ultraviolet absorption identified the resin acid abietic acid, the fatty acids linoleic, linolenic, and palmitoleic acid, and the sterols β-sitosterol and campesterol as present in the extracts. The amount of each compound extracted increased with increasing pressure, with the proportion of abietic acid and β-sitosterol in the extract increasing as the pressure increased. The flavonoid dihydroquercetin was not found in the extracts, even with the addition of the co-solvent methanol.

This Thesis describes the use of supercritical carbon dioxide as both a reaction solvent and processing medium for synthesis new polymeric materials. Chapter 2 details the high pressure equipment used for this body of work, as well as the analytical techniques employed. This includes equipment details for a new high pressure cell designed for measuring small angle x-ray scattering of polymers in situ. Chapter 3 describes the homopolymerisation of both methyl methacrylate and styrene in a supercritical carbon dioxide expanded phase system. Effects of molecular weight and viscosity on the final reaction product are probed in order to ascertain the most suitable types of polymers to be synthesised by this method. This is then extended to create low molecular weight block copolymers in the absence of any volatile organic solvents, with comparable properties to those produced by conventional methods. The development of the high pressure cell for measuring small angle x-ray scattering of block copolymers synthesised in a supercritical carbon dioxide dispersion polymerisation in situ is described in Chapter 4. Initial investigations showed problems with the synthesis in this new vessel, with different products obtained compared to a conventional autoclave. However, data is presented to display the suitability of certain aspects of the design and that scattering patterns can be acquire in situ during a polymerisation. Details of a second modified design are presented, with construction currently in progress. Finally, a green synthetic route to producing renewable, biodegradable and biocompatible polymers is presented in Chapter 5. By using supercritical carbon dioxide to lower the melting temperatures of the monomers, polymerisations usually conducted at temperatures in excess of 130 °C were successfully conducted at 80 °C. Through the use of a novel zirconium catalyst the tacticity of poly(lactic acid) was controlled, opening up a route to functional materials.

The work undertaken involved the exploration of CO2 electroreduction systems, focussing heavily upon electrocatalysis utilising an array of electrochemical, spectroelectrochemical and spectroscopic techniques. The identification and characterisation of a relatively inexpensive and simple electrocatalyst for CO2 reduction was achieved, with the optimisation and development undertaken in such a manner that not just the electrocatalytic species, but also the entire electrochemical system was investigated, in order to determine and better understand the roles played by the various components. The complex of interest, Mo(CO)4bpy, represents the first molybdenum based molecular electrocatalyst reported to be active toward CO2 reduction, despite the prominence of Mo in enzymes with analogous function. The electrochemical characterisation of the complex in the both the presence and absence of CO2 was undertaken, yielding valuable information on the redox behaviour of the complex within the non-aqueous system in which it was employed and highlighting previously unreported features such as a third reduction and new reoxidation attributed to the reoxidation of a tricarbonyl anionic species. Non-aqueous solvents were chosen as they provide greater CO2 solubility than water with portions of the investigation undertaken in tetrahydrofuran, THF, then moving to the less widely used N-methylpyrrolidone, NMP. NMP is significantly less volatile than THF and has a large negative electrochemical window so is ideal for looking at reduction processes and, importantly, is also used as a commercial CO2 scrubbing solvent. Upon addition of CO2 to the Mo(CO)4bpy system there was an observable lowering of the overpotential by over 300 mV, and significant increase in CO2 associated current when compared to that for ‘direct’ CO2 reduction within the same system, at the reduction potential associated with the first reduction of the tetracarbonyl bipyridyl species. The confirmation of the anionic radical as the active species was attained through DFT calculation and EPR spectroelectrochemistry. Under inert gas the spectrum rapidly generated upon application of the first reduction potential is consistent with the expected response for the radical anionic [Mo(CO)4bpy] •−. When the system is saturated with CO2 this radical is no longer detectable. This supports the idea that the unpaired electron is transferred from the [Mo(CO)4bpy]•− to the CO2 molecule and also suggests that this transfer is rapid as no adduct is detectable via EPR even at reduced temperature (240 K). This is in keeping with the rate constants calculated from the voltammetric measurements made. The stability and activity toward CO2 reduction exhibited by Mo(CO)4bpy displayed a strong dependence on working electrode material, with gold proving optimal, indicative of adsorption being significant in the process. Optimisation of both the catalyst structure and the solvent and electrolyte system were also explored, as well as the (somewhat less directly related) comparison of various sources of diffusivity data.

In this study, CO2 adsorption in the presence and absence of co-adsorbed H2O was investigated on different nanomaterials including nanocrystalline NaY zeolite (nano NaY), ZnO, MgO and λ-Al2O3 nanoparticles as well as mixed phase aluminum nanowhiskers. In the case of nano NaY, FTIR spectra show that a majority of CO2 adsorbs in the pores of these zeolites in a linear complex with the exchangeable cation. Most interesting is the formation of carbonate and bicarbonate on the external surface of nano NaY zeolites, suggesting unique sites for CO2 adsorption on the surface of these small nanomaterials. Adsorption of 18O-labeled carbon dioxide and theoretical quantum chemical calculations confirms the assignment of these different species. For aluminum oxyhydroxide nanowhiskers and gamma alumina in the absence of co-adsorbed water, CO2 reacts with surface hydroxyl groups to yield adsorbed bicarbonate as well as some carbonate. C18O2 adsorption confirms these assignments. In the case of nanoparticulate ZnO, CO2 adsorption under dry conditions results in formation of carbonate, bicarbonates as well as carboxylates. However, in the presence of co-adsorbed water, only carbonate species is formed. 18O-labeled carbon dioxide adsorption and theoretical quantum chemical calculations confirm the vibrational assignment for these different species. Mixed isotope studies with H216O + C18O2 and H218O + C16O2 suggest that there is extensive exchange between oxygen in adsorbed water and oxygen atoms in gas-phase carbon dioxide. CO2 adsorption on MgO surfaces, under dry conditions results in formation of carbonate and bicarbonates. Implications for the use of these nanomaterials in carbon dioxide uptake and storage are discussed.

This research was conducted to quantify short- and long-term effects of atmospheric carbon dioxide on wheat. Growth, development, and yield of the spring wheat cultivar Veery-10 were measured in response to CO2 concentrations of 340 (ambient), 1200, and 2500 μmol moI-1 of CO2 air. These 3 CO2 levels were chosen to provide a control group, a predicted optimal CO2 environment, and a potentially toxic CO2 environment, respectively. A recirculating hydroponic system provided a near-optimal root-zone environment that was identical for all CO2 treatment levels. Environmental factors, other than CO2, were controlled at near optimal levels, although photosynthetic photon flux was actually suboptimal and higher levels would increase growth. Standard growth analysis procedures were used to measure growth rates and carbon partitioning to leaves, stems, and roots. Yield components were measured on mature plants. Because elevated CO2 levels may increase growth by increasing radiation absorption or by increasing photosynthetic efficiency, measurements of absorbed photosynthetic photon flux were calculated from measurements of incident, reflected, and transmitted photosynthetic photon flux. Growth and yield were increased by the 1200 μmol moI-1 of CO2 in air treatment in all trials. Growth and yield were reduced by the 2500 μmol moI-1 treatment in both long-term trials, but growth was not reduced by this treatment in two short-term trials. These data indicate that CO2 is toxic to wheat at 2500 μmol moI-1 (0.25%), but the effects are not expressed until the last half of the life cycle.

Emissions from the combustion of fossil fuels and cement production are responsible for approximately 75% of the increase of carbon dioxide (CO2) concentration in the atmosphere. 80% of the generated world energy is produced by burning fossil fuels (IPCC 2007) and such tendency is likely to remain unchanged in the nearest future. These number look more intimidating if consider the fact that in 2030, global energy demand was estimated to increase by 57% in comparison to 2004 (from 14.9 terrawatts (TW) in 2004 to 23.4 TW in 2030; International Energy Outlook 2007). Moreover, only 45% of CO2, released due to human activity since 1959, is absorbed by the nature (plants and the ocean) (IPCC 2007). Thus, the other 55% of CO2 from human activity remains in the atmosphere undeniably causing serious changes in the Earth‟s climate.With the potential impact of climate changes there is a considerable motivation to find solutions for reducing greenhouse gas emissions, particularly CO2. Moreover, the development of alternative energy sources is a commercially important task considering the fact that fossil fuels are non-renewable resources and will eventually deplete. It is well known that CO2 is a cheap and abundant source of carbon. Thus, the conversion of CO2 into fuels can be considered as a prospective method providing the possibility of CO2 recycling and as a result the decrease of CO2 concentrations in the atmosphere. Thus, over the past decades an increasing amount of global research efforts has focused on developing a CO2 utilization system. However, because CO2 is a very stable molecule, a large amount of energy is required to initiate its reduction. So the invention of an economically feasible method is the primary task in development of a CO2 reduction technology. The vast majority of work in this direction devoted to:- the application of new catalysts for CO2 reduction processes,- the use of various semiconductor technologies to harness solar energy as the energy input to the reaction of CO2 reduction, and- the development of bio-inspired processes in order to amplify the photosynthesis process in living organisms or create the artificial photosynthesisAn area of investigation that has received less attention is that of sonochemical reduction of CO2, or the use of ultrasound irradiation to reduce CO2 to basic fuel stock components. The chemical effect of ultrasound comes from acoustic cavitation phenomena – the formation, growth and collapse of cavitation bubbles. The collapse of cavitation bubbles results in generation of micro-zones of extremely high temperature (over 5000 K) and pressures (300 bar) (Nolting, and Nepparis 1950) which is the driving force for sonochemical reactions. Molecules trapped in cavitation bubbles undergo processes of radicalization and recombination due to the great amount of energy generated during the cavitation collapse.This thesis is devoted to experimental investigation of chemical utilization of CO2 using ultrasound as a source of energy. Sonochemical reduction of CO2 in various sonicating media is carried out in a wide range of experimental conditions. The main idea behind the experimental work performed is to investigate the ways of CO2 utilization into useable chemicals by its direct sonolysis or recombination of it with H2 while using the ultrasound (vibrational) energy, provided by the 20 kHz ultrasonic probe system. The study on sonochemical fixation of dense-phase and supercritical CO2 is also conducted. The efficiency and prospective usage of ultrasonic energy in the process of CO2 reduction is estimated based on the experimental results obtained. Additional study of the ultrasound-assisted oxidative desulfurization process of sulphur containing compounds by potassium permanganate (KMnO4) is conducted in order to investigate the effect of ultrasound on oxidation processes.

Biochar is increasingly gaining momentum in the context of climate change mitigation and its production in Sweden could potentially become a large-scale system. Carbon stability in biochar is a crucial factor to assess its the carbon sequestration potential. Currently specific methodologies to assess biochar carbon site-specific stability are missing. This work aims at filling in part this knowledge gap assessing stability for Sweden specific soil conditions. Moreover, this work aims at assessing biomass feedstock availability for biochar production from a system perspective and aims at estimating biochar production and carbon dioxide removal potentials in Sweden. Preliminary carbon stability specific thresholds are provided for soils at 10°C temperature and, thus, representative for Sweden conditions. Carbon dioxide removal functions are obtained for different feedstock categories (woody, herbaceous, biosolids and animal waste) dependent on pyrolysis conditions (Highest Treatment Temperature), and conditions for maximum carbon removal are assessed. The need for future analysis in order to validate the presented results is highlighted. Future work should focus on collecting new experimental results of biochar mineralisation based on the requirements presented in this work. An opportunity mapping for biochar production system is provided, focusing on some aspects of the interaction of the former with existing systems (agricultural, energy production and waste management). From the results of the opportunity mapping, an inventory of the available feedstock for biochar production is presented including woody residues, sewage sludge, manure, garden waste and straw. From the available feedstocks, biochar production and carbon dioxide removal potentials are estimated to range respectively between 0.9 and 1.7 million tbiochar/year and between 2 and 4.2 million tons CO2 sequestered per year (in a 100 years perspective). In terms of carbon dioxide removal potential, biochar production can significantly contribute to the goals set by Sweden in terms of climate change mitigation and emission offsetting for 2030 and 2045, potentially covering all the measures needed from carbon sinks from forest and land. It was found that the most significant contribution derives from the availability of woody residues in Sweden, whose analysis should be prioritised for future assessment of feasibility of biochar large scale production.

La present tesi de nom “Estratègies organocatalítiques per a la síntesi i transformació de carbonats cíclics” recull una sèrie d'avanços a l'àrea de la valorització del diòxid de carboni. En primer lloc, s'exposa breument la situació actual del camp, així com els organocatalitzadors més utilitzats i una discussió general relativa als aspectes mecanístics de les reaccions que tenen lloc en aquests processos. En segon lloc, es realitza la síntesi de carbonats cíclics terminals amb ajuda d'un compost natural, utilitzat com un organocatalitzador, “l’àcid tànnic”. A més, es duu a terme un estudi comparatiu de l'activitat i el temps de vida del catalitzador, així com el desenvolupament d'un protocol de separació i reciclatge del mateix. En tercer lloc, s’aconsegueix la síntesi de carbonats disubstituïts mitjançant l’ús d’esquaramides com organocatalizadors. Aquestes esquaramides, a més d'oferir un gran ventall d'opcions per modular la seva activitat i solubilitat, presenten punts d'ancoratge per poder suportar el catalitzador en una matriu heterogènia. Aquest treball recull també un estudi relatiu al mecanisme de reacció alternatiu que té lloc. El quart capítol tracta sobre la síntesi de carbonats tri i tetrasubstituïts seguint un plantejament totalment diferent als dos capítols anteriors i que no requereix l'ús de sistemes catalítics binaris. El present estudi es basa en l’interconversió de carbonats cíclics i el desplaçament d’aquest equilibri cap a la formació del carbonat més substituït. Finalment es completa la síntesi de carbamats per mitjà de la aminòlisi dels carbonats cíclics anteriorment sintetitzats. Gràcies a l'ús del “TBD” com a catalitzador, el procés experimenta una millora espectacular relativa a les condicions de reacció i a la regioselectivitat.
La presente tesis de nombre “Estrategias organocatalíticas para la síntesis y transformación de carbonatos cíclicos” recoge una serie de avances en el área de la valorización del dióxido de carbono. En primer lugar, se expone brevemente la situación actual del campo, así como los organocacatalizadores más utilizados y una discusión general relativa a los aspectos mecanísticos de la reacciones que tienen lugar en dichos procesos. En segundo lugar, se lleva a cabo la síntesis de carbonatos cíclicos terminales con ayuda de un compuesto natural, utilizado como organocatalizador, el “ácido tánico”. Además, se lleva a cabo un estudio comparativo de la actividad y el tiempo de vida del catalizador, así como el desarrollo de un protocolo de separación y reciclaje del mismo. En tercer lugar, se lleva a cabo la síntesis de carbonatos di sustituidos mediante el empleo de esquaramidas como organocatalizador. Dichas esquaramidas, además de ofrecer un gran abanico de opciones para modular su actividad y solubilidad, presentan puntos de anclaje para poder soportar el catalizador en una matriz heterogénea. Dicho trabajo recoge también un estudio relativo al mecanismo de reacción alternativo que tiene lugar. El cuarto capítulo trata sobre la síntesis de carbonatos tri y tetra sustituidos siguiendo un planteamiento totalmente diferente a los dos capítulos anteriores y que no requiere el empleo de sistemas catalíticos binarios. El presente estudio se basa en interconversión de carbonatos cíclicos y el desplazamiento de dicho equilibro hacia la formación del carbonato más sustituido. Finalmente se lleva a cabo la síntesis de carbamatos por medio de la aminolisis de los carbonatos cíclicos anteriormente sintetizados. Gracias al uso de TBD como catalizador, el proceso experimenta una mejoría espectacular relativa a las condiciones de reacción y a la regioselectividad.
The following thesis “Organocatalytic strategies towards the synthesis and transformation of cyclic carbonates” contains new advances in the field of carbon dioxide valorization. First, the state of the art in the field is presented, as well as the most used organocatalysts and general remarks about the reaction mechanisms involved in those processes. Second, the synthesis of terminal cyclic carbonates with the help of a natural compound used as organocatalyst (tannic acid”) is studied. In this work a comparative study in terms of activity and life time of different organocatalysts is carried out, as well as the development of a new separation and recycling protocol. Third, disubstituted cyclic carbonates are synthesized with the use of squaramides as organocatalysts. Those catalysts can be easily synthesized and different properties such as solubility and catalytic activity can be easily modulated. The alternative mechanism related to this transformation is studied and supported via spectroscopic data. The forth chapter is about the synthesis of tri and tetra substituted cyclic carbonates following a totally different approach that avoid the use of a binary catalytic system. This transformation is based in the interconversion of different cyclic carbonate structures and the displacement of the equilibrium towards the formation of the most substituted product. Finally, the synthesis of carbamates via aminolysis reaction of the previously synthesized cyclic carbonates is carried out. Here in, TBD is used as catalyst, and the reaction conditions and the regioselectivity of the process is improved spectacularly.

Carbon Dioxide (CO2) emission from hydrocarbon fuel combustion is becoming a serious concern because it is the main contributor to greenhouse gas which causes global warming. Activated carbon sorbents have been used widely in various gas-phase and/or liquid-phase separation. Currently activated carbon (AC) is being investigated and developed for CO2 capture. Chicken waste, which is produced in large quantity in U.S., is currently disposed as waste. However, it may have a large benefit to turn chicken waste into useful activated carbon. In this research, a series of activated carbon have been generated from chicken waste and coal in the lab scale reactor. The characteristics of these generated activated carbons, such as specific surface, thermal stability, structure properties were investigated and discussed. The CO2 adsorption capabilities of these activated cartons were also studied in pure CO2 system and CO2/H2O system. One of these activated carbons was modified using the acid treatment, which improved the CO2 adsorption capacity by around 4 times.

The aim of this project is the design, synthesis and characterisation of porous carbon structures capable of the selective capture of carbon dioxide (CO2) from the exhaust gases of coal and gas post-combustion power stations. In such systems, the fossil fuel is burnt in an air environment producing CO2 as just one of a multi-component flue gas. This flue gas is expected to contain nitrogen and water among other constituents. It is at ambient pressures and temperatures of ≥323 K. Successful capture materials should have highly microporous structures, rapid sorption kinetics and be capable of repeated sorption/desorption cycles. To develop highly microporous carbon sorbents a range of porous materials have been synthesised using chemical and physical activation of precursors obtained through top down and bottom up approaches. Porosity has also been achieved in precursors through the controlled use of graphene exfoliation, melamine-formaldehyde resin aerogel formation, soft templates, controlled carbonisation and synthesis of microporous organic polymers. The role of nitrogen dopants (N-dopants) within the CO2 sorbent materials has also been investigated. To increase understanding and tune the sorbents performance, porous carbon structures have been synthesized containing: pyridine, pyrrole, quaternary and triazine nitrogen groups. Characterisation was achieved using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, transmission electron microscopy X-ray diffraction, thermogravimetric analysis and nitrogen (N2) isotherms at 77 K. CO2 sorption analysis was carried out using volumetric and gravimetric analysis. The influence of N-dopants on the adsorbate-adsorbent interaction is characterised using CO2 volumetric isotherms, isosteric heats of adsorption and CO2/N2 selectivity analysis.

Diese Dissertation handelt vom metastabilen Zerfall und von der Oberflächenwechselwirkung im hyperthermalen Energiebereich relativ schwach gebundener molekularer Kohlenmonoxid und Kohlendioxid Clusterkationen mit einer Edelstahloberfläche und einer Siliziumoberfläche. Im Rahmen dieser Arbeit wurde ein hierfür geeignetes spezielles Flugzeitmassenspektrometer entwickelt und aufgebaut. Entwurf, numerische Optimierung der Auflösung, ionenoptische Simulationen und Aufbau der jeweiligen Komponenten wie Elektronenquellen, Beschleuniger, Ablenkplatten, Massenfilter und Reflektron werden detailliert beschrieben. Das entwickelte Flugzeitmassenspektrometer besitzt mit einer kompakten Gesamtfluglänge von ~1.5m eine hohe Massenauflösung von m/Delta m = 3000. Es bietet die Möglichkeit, eine Massentrennung von Clusterionen mit einer Größe von bis zu n = 190 vorzunehmen. Diese massenselektierten Clusterionen können daraufhin auf metastabilen Zerfall und auf ihre Wechselwirkung mit einer Oberfläche untersucht werden. Dazu wurden Kohlendioxid-Clusterionen mit n
This thesis deals with the metastable decay and the surface scattering in the hyperthermal energy range of relatively weakly bound molecular cluster cations. With carbon monoxide and carbon dioxide two related model systems were chosen for a systematic size dependent study. Surface impact experiments were carried out with stainless steel and silicon surfaces. Results were obtained by a new, reflectron time-of-flight mass spectrometer (Re-TOFMS). Additional to the experimental data we present in this work a detailed description of the instrumental design considerations, numerical optimization, ion optical simulations. Hence each ion optical component like electron guns, accelerator, deflector, mass gate and reflectron are described. Despite the compact dimensions with a total flight length of ~1.5m the developed instrument possesses a high mass resolution above m/Delta m = 3000. Additionally it offers the possibility to perform mass separation of big cluster ions with sizes n

En les darreres dècades, la catàlisis homogènia ha aconseguit un paper destacat dintre de la indústria química. També ha tingut un gran impacte en els últims anys l'ús de dissolvents alternatius com a medis de reacció per evitar l'ús de dissolvents orgànics que són tòxics i tenen un impacte mediambiental molt elevat. L'ús del diòxid de carboni supercrític (scCO2) com a medi de reacció, a part de ser de baix cost, no ser tòxic, no ser inflamable, presenta les avantatges de permetre reciclar fàcilment el catalitzador, tenir una elevada solubilitat amb els gasos i permetre modular les seves propietats fàcilment canviant la pressió i temperatura. Una de les propietats d'aquest solvent és la baixa polaritat del medi, això fa que la solubilitat dels sistemes catalítics es vegi afectada en funció dels reactius utilitzats.
En aquest context, l'objectiu principal d'aquesta tesis és la realització de reaccions de carbonilació, com hidroformilació, hidrocarboxilació, hidroesterificació i copolimerització, utilitzant com a medi de reacció el diòxid de carboni supercrític. Per duu a terme aquestes reaccions en scCO2 s'han utilitzat sistemes catalítics modificats, és a dir, s'han sintetitzat lligands P- o N- donadors amb cadenes alquíliques perfluorades o s'han incorporat al sistema surfactants com perfluoropolièters o ciclodextrines amb grups acetats, que fan que el sistema es solubilitzi més fàcilment en el medi.
En la introducció s'ha fet un recull bibliogràfic de les reaccions de carbonilació en dissolvents orgànics, dels lligands més utilitzats en aquests tipus de reaccions i dels cicles catalítics que tenen lloc. També s'ha fet una introducció de les propietats i l'ús del diòxid de carboni en estat supercrític i de la seva aplicació en les reaccions de carbonilació.
S'ha estudiat la reacció d'hidrocarboxilació d'alquens lineals en diòxid de carboni supercrític. Com a sistema catalític s'ha utilitzat un precursor de pal·ladi(II) [PdCl2(PhCN)2], associat amb fosfines perfluorades (Figura 1).

Figura 1

S'ha realitzat un estudi de solubilitat i de l'activitat catalítica en scCO2 dels diferents sistemes catalítics. El millor sistema catalític ha estat [PdCl2(PhCN)2]/1 quan es duia la reaccions en sistemes no solubles. En aquest sistema s'ha obtingut 55% de conversió, 90% de selectivitat amb àcids i l/b=3 a 150 atm de pressió total i 90ºC. També s'ha estudiat l'activitat de la reacció amb el mateix sistema però addicionant un perfluoropolièter (sal d'amoni de Krytox) com a surfactà, millorant així els resultats obtinguts (93% de conversió, 77% de selectivitat en àcids i l/b de 4.5). També s'ha estudiat mitjançant tècniques d'alta pressió de ressonància magnètica nuclear(HPNMR) les espècies formades in situ en condicions similars a les de reacció.
També ha estat estudiada la reacció d'hidroesterificació d'1-hexè en scCO2 utilitzant els mateixos sistemes. El millor resultat però, ha estat amb el sistema [PdCl2(PhCN)2]/2 amb el que s'han obtingut 67% de conversió i 64% de selectivitat amb èsters.

Referent a la reacció de copolimerització amb CO i tert-butilestirè en scCO2. Per duu a terme la reacció s'han utilitzat lligands nitrogen-donadors amb cadenes perfluorades (Figura 2) amb els que s'han sintetitzat complexos dicatiònics de pal·ladi(II) [Pd(5,6,7,8)2]X2.


Figura 2
S'ha estudiat la solubilitat de tots els complexos en scCO2 i s'ha vist que tots ells són solubles en aquest medi.. S'ha estudiat l'activitat catalítica dels diferents lligands a diferents pressions de CO2, observant que la selectivitat de la reacció canvia en funció del lligand. Els millors resultats s'han obtingut amb el complex [Pd(5)2](BArF)2, a baixes pressions de CO2, amb el que s'han obtingut 1.4 Kg de copolímer gPd-1, amb un pes molecular de 167000 i una estereoregularitat del 90%.

Finalment, s'ha estudiat la hidroformilació d'1-octè en scCO2. S'han sintetitzat quatre fosfits, dos derivats del fenol (9-10) i dos derivats del benzil alcohol (11-12), amb grups -CF3 (Figura 3).

Figura 3

S'ha estudiat la coordinació d'aquests lligands en complexos catiònics de rodi(I) observant que els lligands amb menys impediments estèrics (9-10) es coordinen formant complexos [Rh(9-10)4]X, mentre que els lligands 11-12 formen complexos [Rh(cod)( 11-12)2]X. S'ha estudiat la reactivitat amb CO i H2 dels sistemes de rodi [Rh(CO)(acac)] amb els lligands 9-12 per RMN i IR d'alta pressió (HPNMR, HPIR) en condicions similars a les catalítiques. També s'ha estudiat la reactivitat catalítica dels quatre sistemes en diferents pressions de CO2 i amb toluè per poder comparar el sistema en un solvent orgànic. L'activitat obtinguda en la reacció en scCO2 per als sistemes Rh/9,10,12 és similar o superior a l'obtinguda amb toluè, encara que la selectivitat va ser més baixa. En canvi, per al sistema Rh/3, la selectivitat obtinguda amb scCO2 va ser major que l'obtinguda amb toluè. La relació n/iso obtinguda per al sistemes Rh/10-12 va ser superior amb scCO2.
Els millors resultats s'obtenen amb el sistema [Rh(CO)(acac)]/9, que proporciona 99% de conversió, 60% de selectivitat i una relació n/iso de 7.3; i amb el sistema [Rh(CO)(acac)]/ 12 amb el que s'ha obtingut 93% de conversió, 62% de selectivitat i una relació n/iso de 4.
Dins d'aquest tema també s'ha estudiat la hidroformilació d'1-octè en scCO2 utilitzant un sistema inicialment insoluble, del qual amb l'addició d'una ciclodextrina amb grups acetats (16, Figura 4) s'ha aconseguit augmentar-ne la solubilitat. El sistema insoluble està format per [Rh(CO)2(acac)] amb lligands P-donadors amb cadenes alquíliques ramificades (13-15).

Figura 4

L'activitat catalítica dels sistemes [Rh(CO)2(acac)]/13-15 (Figura 4) es millora afegint la ciclodextrina. Malauradament, la selectivitat en aldehids disminueix, possiblement degut a la descoordinació del lligand (13) al introduir-se a la cavitat de la ciclodextrina.
Homogeneous catalysis has achieved an important role in chemical industries in the last decades. A recent aspect of this role that is receiving increasing attention is the use of alternative reaction media that solve the environmental problems associated with many of the traditional volatile organic solvents. The use of non-conventional reaction media also provides opportunities for facilitating the recovery and recycling of the catalyst. Among these reaction media, supercritical carbon dioxide(scCO2) is an interesting solvent in the context of green chemistry and catalysis in several mono- and biphasic systems.
The use of scCO2 as a solvent, a part it is economic, non-toxic, non-flammable, has the advantage to recycle easily the catalyst, has high miscibility with gases and it is easy change its properties changing temperature or pressure. The main limitation is the low polarity of the media which lead to low solubility of the catalytic systems.

The aim of the present thesis is to use supercritical carbon dioxide as alternative solvent for different catalytic carbonylation reactions such as hydroformylation, hydrocarboxylation, hydroesterification of long chain alkenes and copolymerisation of carbon monoxide and tert-butylstyrene. To afford solubility in that system, different attempts have been used: synthesis of perfluorinated phosphorus or nitrogen donor ligand or the use of acetylated cyclodextrin or perfluoropolyether molecules as solubilizer agents.
The hydrocarboxylation of linear alkenes using scCO2 as a solvent has been studied. It was used a palladium (II) precursor with fluorinated phosphines (Figure 1).

Figure 1
The solubility of the systems in supercritical carbon dioxide was studied. The best system for the reaction was [PdCl2(PhCN)2]/1 at non-soluble conditions, obtaining 55% of conversion, 90% of selectivity and l/b =3. The activity of the system adding an ammonium salt of Krytox as a surfactant. It showed an increase in the conversion (93%) and in the regioselectivity (l/b=4.5) although the selectivity decrease(77%).
By HPNMR spectroscopy, the species formed at similar conditions than hydrocarboxylation were studied observing the formation of Pd(0) species which by reacting with an acid could produce the hydride active species of the mechanism.

The hydroesterification of 1-hexene was studied using the same Pd-systems. The best conditions were obtained with system was [PdCl2(PhCN)2]/2/MeOH at non-soluble conditions.

Regarding to CO/tertbutylstyrene copolymerisation in scCO2, different palladium bischelated complexes were synthesised and characterised [Pd(5,6,7,8)2]X2. All of this complexes were soluble in liquid and supercritical carbon dioxide.

Figure 2
The best result was obtain in liquid expanded CO2, using [Pd(5)2](BArF)2, obtaining 1.4 Kg copolymer/g Pd, 167000 of molecular weight and 90% of syndiotacticity.

Finally the hydroformylation of 1-octene was studied in scCO2. CF3-groups phosphites were synthetised from phenol (9-10) and from benzylalcohol (11-12) (Figure 3).

Figure 3

The reactivity of them with CO/H2 were studied by HPNMR and by HPIR, observing as a major species formed [HRh(9-12)3(CO)].
The catalytic experiments were carried out in toluene and in scCO2. Comparing both solvents, the conversion were better then toluene or similar for the systems Rh/9,10,12 although the selectivity decrease. However, for Rh/11 the selectivity obtained in scCO2 was higher then in toluene.

The effect of addition a peracetylated cyclodextrine (Figure 4, 16) to increase the solubility of a non-soluble rhodium system Rh/13-15 (Figure 4) was studied.


Figure 4
The system became soluble at 250 atm and 80 ºC. The addition of the cyclodextrine increase the conversion and the l/b ratio of the hydroformylation of 1-octene although the selectivity decrease, probably Per-Ac-β-CD may favour the dissociation of the ligand 13-15 from the catalytic species. In the scCO2 medium, this dissociation could be very high and would lead to free ligand catalytic species which favour the isomerisation.

Thesis (Ph. D.)--Ohio State University, 2005.
Title from first page of PDF file. Document formatted into pages; contains xviii, 226 p.; also includes graphics (some col.). Includes bibliographical references (p. 206-226). Available online via OhioLINK's ETD Center

Supercritical fluids have unique properties which may make them ideal as reaction media for biotransformation or extractive solvents. Supercritical fluids are ideal for reducing diffusivity limitations over conventional fluids. Depending on the polarity of the fluid, a supercritical fluid can be similar to conventional organic solvents, but with few of the environmental drawbacks. The use of supercritical fluids in enzymatic research has the advantage of removing mass transport limitations so that they can act as a suitable solvent. In this study, four permeabilization techniques were compared: control, toluene, supercritical carbon dioxide, and freeze/thaw cycles. The model cell systems studied were Z. mobilis and E. coli. The cells were analyzed for lipid profiles, recovery of proteins and enzymatic activity. The use of supercritical carbon dioxide may not be the most effective of the treatments based on total protein or enzyme recovery since the greatest protein and enzyme recovery was with the freeze/thaw treatment. However, it can be selective in removing cofactors from Z. mobilis enabling sorbitol production and minimizing side reactions. In this application, supercritical carbon dioxide does show an advantage over the freeze/thaw treatment. Aspects of the mechanism of permeabilization were investigated based on the lipid profiles of the cells, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The SEM and AFM show changes of the cell surface morphology which indicate that the treatments affect the cellular surface. The use of supercritical carbon dioxide as a reaction medium was investigated. Minute quantities of sorbitol were produced when Z. mobilis and sugars were placed in a supercritical carbon dioxide environment over a period of 24 hours.

The average energy consumption of one ice rink is around 1000MWh/year, which approximately69% is occupied by the refrigeration unit and heating demand. With the aim of decreasing theenergy consumption, a new concept of refrigeration system with CO2 as a refrigerant has beendeveloped and it is promising to become a high potential next generation for refrigeration systemin ice rink.This thesis is to evaluate a new refrigerant application in ice rink refrigeration system underthree different aspects; energy performance, heat recovery potential and economic efficiency. Inorder to make this evaluation, three main tasks are executed. Firstly, literature review and marketstatistic are processed to give a general picture of the CO2 development as a refrigerant. Secondly, asoftware Pack Calculation II is used for the simulations of CO2 refrigeration system and traditionalice rink refrigeration system. Älta ice rink located in Sweden, is chosen as a reference case forsimulation’s input data. The simulation results is to compare these system in terms of energyperformance and heat recovery potential. Finally, life cycle cost of these systems is calculated toinvestigate the economic benefits from this new application.Results from this study show good benefits of the new CO2 application in ice rink. Fromthe market statistics, CO2 has become a successful refrigerant in supermarket food and beverageindustry with 1331 CO2 refrigeration system installed until 2011 in Europe (Shecco2012). In icerink industry, 24 ice rinks have been applied CO2 in the second cycle of refrigeration system; oneice rink in Canada applied a refrigeration system with only CO2 in the first cycle and the distributionsystem.From the simulation’s result, CO2 full system has been proven as the most efficiency sys-tem with the lowest energy consumption (30% lower than NH3/Brine system and 46% lower thanCO2/Brine system) and the highest COP (6.4 in comparison with 4.9 of NH3/Brine system and4.37 of CO2/Brine system). Regarding heat recovery potential, CO2 full system has highest energysaving in comparison with the other two systems.Due to lower energy cost and service cost, the life cycle cost of CO2 full system is loweraround 13% than the traditional NH3/Brine system, furthermore, the component cost of CO2 sys-tem is promising to decrease in the next years thanks to the rapid development of this market insupermarket industry.To conclude, CO2 full system has high potential to become a next generation of refrigerationsystem in ice rink, however, because of its transcritical working, this application can be restrictedin the regions of warm climate.

The Petronas C02 project aimed to design an ionic liquid-based technology for the removal of C02 from natural gas. Current technology using amine-based system is not economical. It is envisioned that an ionic liquid method has the potential to be superior to current technology, due to their unique characteristics, such as high thermal stability, negligible vapour pressure and the possibility to fine-tune their properties, by combining appropriate cations and anions. This project involved the development of a "simple" synthetic method for ionic liquids, utilising Group 2 metal hydroxides (especially, strontium hydroxide octahydrate). This gave a wide array of carboxylate ionic liquids, via an intermediate hydroxide solution. It is a very simple, straightforward procedure which uses starting materials which are commercially available in bulk. The classes of carboxylate ionic liquids that have been synthesised and fully characterised are those based on the cations: l-ethyl-3-methylimidazolium, tributylmethylammonium, tetraalkylphosphonium and l -al kyl -l-methylpyrrolidinium. The Hunig's based derivatives of l -alkyl•3•methylimidazolium bistriflamides, as well as phosphonium and ammonium caboxylates were tested for their ability ty to absorb C02. In the anhydrous us system, initial screening showed that the most promising anions for C02 solubility are the methanoate and ethanoate. In parallel, it was observed that the C02 solubility in ionic liquids was not greaby the alkyl chain length on cation. The most noticeable effect on C02 capture was the addition of 1 mole of water to the carboxylate ionic liquids. This greatly enhanced the solubility of C02 by an order of magnitude, which is due to a different mechanism of C02 absorption; chemisorption on in the presence of water, instead of physisorption. A mechanism via the formation of hydrogencarbonate has been proposed due to this remarkable ability for C02 capture, which was later proven by other team members. All in all, the system that has been put forward for consideration as a potential C02 absorber in industrial processes within Petronas is the equimolar system of [4441][CH3C02] and water .

A review of sensors for carbon dioxide and oxygen, with special focus on optical sensors, is presented in Chapter 1. The major experimental procedures and materials used in the PhD research project are given in Chapter 2. The results of a study of the use of different plasticisers, including phosphate-, phthalate- and adipate-based types for the creation of a range of colourimetric plastic film sensors for carbon dioxide are reported in Chapter 3. The response characteristics, i.e., carbon dioxide sensitivity and the response/recovery times are studied when different types of plasticiser are used in the formulation of a sensor for carbon dioxide. Of the types of plasticisers used in this work, the most efficient appeared to be phosphate-based. Chapter 4 describes the results of an investigation of the response characteristics, i.e., carbon dioxide sensitivity, temperature and response/recovery characteristics, of a plastic film colourimetric sensor for carbon dioxide when a small amount of aromatic alcohol, such as m-cresol, is included in the film formulation. The effects on the carbon dioxide sensitivity containing different aromatic alcohols is also examined. Chapter 5 investigates the luminescent ruthenium ion-pair [Ru(dpp)₃²⁺(Ph₄B^-)₂] incorporated into the hydrophobic medium of the polymer, poly(vinyl chloride), plasticised with tributyl phosphate. A detailed study on the response characteristics, i.e., film sensitivity towards oxygen and response and recovery times, were studied as a function of plasticiser content, temperature and stability in use, and with age. The major response characteristics depend very strongly upon the overall level of plasticiser present in the film. In Chapter 6, pyrene is incorporated into a number of polymer-plasticiser encapsulation media for the creation of a new range of luminescent plastic film sensors for optical sensing of oxygen. Furthermore, pyrene and Reichardt's dye are used as single polarity probes of the encapsulation medium in an attempt to correlate the oxygen-sensitivity of a pyrene-based oxygen sensor and the encapsulating medium polarity.

The research described in this thesis relates to the development and optimisation of a novel polymerisation reaction and its subsequent use in the generation of novel ‘Polymers of Intrinsic Microporosity’ (PIMs). The polymerisation reaction takes monomers containing two or more aromatic amines and fuses them together by the synthesis of a bridged bicyclic heterocyclic link called Tröger’s base (TB). This link not only strongly holds the polymer chain together, but also provides a site of contortion, which is necessary for a PIM to exhibit microporosity. The first part of this work introduces the background to the research, detailing the reasons behind the development of a new class of PIM and the competitor materials. Following this is detailed the optimisation of the TB forming condensation reaction and the synthesis of a variety of amine functionalised monomers. Also described in this section is the optimisation of a second condensation reaction used for the synthesis of a family of compounds based around a coumaron framework, all of which lack amine functionality. This precedes discussion of X-ray crystal structure analysis of several TB model compounds, amine functionalised monomers and coumaron-based compounds. After this is a description of the development of the novel TB polymerisation reaction, the results of the TB polymerisation of the amine functionalised monomers, characterisation of the successful polymers and the attempted polymerisation of two coumaron-based monomers. The final part of this work reports the experimental procedure for each compound together with full characterisation. In closing, the TB polymerisation reaction has successfully used for the production of highly stable and soluble PIMs exhibiting a wide range of microporosity, with BET surface areas ranging from 0 m2/g to 1035 m2/g. A few of these PIMs have been found to have excellent molecular weight, capable of forming strong membranes, suitable for gas separation, most notably for the purification of oxygen, hydrogen and carbon dioxide from nitrogen. Conversely, the synthesis of coumaron-based PIMs proved unsuccessful, but nevertheless this research should allow the future synthesis of a coumaron-based PIM. The research on TB polymerisation detailed in this thesis has contributed towards an International Patent122 and a paper in Science123so can be deemed to have been successful by that measure.

Carbon dioxide capture is an urgently needed pathway to mitigation of climate change, yet the amine-based solvents currently considered the leading industrial technologies suffer from many shortcomings; namely their high operating cost, poor stability and potentially damaging environmental impact from emission of degradation products. This work is a study of possible routes to improved CO2 capture technologies from a fundamental chemistry perspective. Initial work focused on the development of a straightforward and adaptable protocol for studying the species formed by CO2 capture into amine solvents, using 1H NMR spectroscopy for its combination of speed and accuracy. The applicability of this approach to diverse blended-amine solvents was demonstrated. This method was then applied to the study of phenoxide as a novel possible capture agent in conjunction with amines. Blends of potassium phenoxide with monoethanolamine were found to have an excellent capture capacity and favourable speciation that suggests a low energy consumption in practical use. This demonstrates the feasibility of blended solvents with a reduced amine component. Finally, a possible amine-free route to CO2 capture, exploiting the high susceptibility of carboxylate acidity to solvation, was explored. The first systematic study of the pKa of CO2 in mixtures of organic solvent and water was carried out, finding that this value is relatively insensitive to the makeup of the solvent and therefore in organic-rich solutions, carboxylate salts can be used as a CO2-absorbing base. CO2 capture using a system developed along these principles was demonstrated, and the possible basis for the observed insensitivity was discussed with particular emphasis given to the thermodynamics of the process.

Measurements of leaf and ecosystems scale CO₂ flux were made at the millet, fallow and tiger bush sites at the HAPEX-Sahel Southern supersite. These were analysed in relation to biological and environmental variables. In the five species studied, leaf scale photosynthesis was strongly influenced by photosynthetic photon flux density (Q) and stomatal conductance, and was well described by the non-rectangular hyperbola model of Jarvis, Miranda and Muetzelfeldt (1985). Stem respiration was measured in two species, and increased exponentially with temperature. Stem respiration rates were higher in the wet season than in the dry season and this difference was used to separate growth and maintenance respiration. Effects of Q and sap flow on stem CO₂ efflux were observed. A small number of soil respiration measurements were also made. Direct measurements of leaf area index, biomass and canopy structure were made at the millet and fallow sites. Two indirect methods of estimating leaf area index, from hemispherical photographs and measurements of transmitted Q, were used to all three sites. Together with measurements of canopy structure at each site, the measurements of leaf photosynthesis, stomatal conductance and stem soil respiration were used to parameterise two models which predict ecosystem net CO₂ flux: a simple one-dimensional "big leaf" model and a complex three-dimensional model "MAESTRO". Model predictions were compared with independent ecosystem flux measurements made by eddy covariance. Generally, both models agreed well with measurements at all three sites. Differences between measurements and predictions were very small in millet and largest in tiger bush, and were attributed to the effect of canopy heterogeneity on eddy covariance measurements and the accuracy with which canopy structure parameters could be estimated.

Satellite measurements of atmosphere CO2 concentrations are a rapidly evolving area of scientific research which can help reduce the uncertainties in the global carbon cycle fluxes and identify regional surface sources and sinks. One of the emerging CO2 measurement techniques is a relatively new retrieval algorithm called Weighting Function Modified Differential Optical Absorption Spectroscopy (WFM-DOAS) (Buchwitz et al., 2000). This algorithm is designed to measure the total columns of CO2 (and other greenhouse gases) through the application to spectral measurements in the near infrared (NIR), made by the SCIAMACHY instrument on-board ESA's ENVISAT satellite. The WFM-DOAS technique is based on fitting the logarithm of a model reference spectrum and its derivatives to the logarithm of the ratio of a measured nadir radiance and solar irradiance spectrum. In this thesis, a detailed error assessment of this technique has been conducted and it has been found necessary to include suitable a priori information within the retrieval in order to minimize the errors on the retrieved CO2 columns. Hence, a more flexible implementation of the retrieval technique, called Full Spectral Initiation (FSI) WFM-DOAS, has been developed which generates a reference spectrum for each individual SCIAMACHY observation using the estimated properties of the atmosphere and surface at the time of the measurement.

We modifed a streamlined-based simulator based on the work of Batycky et al. (1997) [7] to solve CO2 transport in aquifers and oil reservoirs. We then use this to propose design strategy for CO2 injection to maximise storage in aquifers and to maximise both CO2 storage and enhanced oil recovery (EOR) in oil reservoirs. We first extended Batycky et al. (1997) [7]'s streamline simulator from two phases (aqueous phase and hydrocarbon phase) and two components (water and oil) to a three- phase (aqueous phase, hydrocarbon phase and solid phase) and four-component (water, oil, CO2 and salt) simulator specialized for CO2 injection. We solved CO2 transport equations in the hydrocarbon and aqueous phases along streamlines and in the direction of gravity. To capture the physics of CO2 transport, in the hydrocarbon phase, we used the Todd-Longsta® (1972) [112] model to represent sub-grid-block viscous fingering. We implemented a thermodynamic model of mutual dissolution between CO2 and water and resulting salt precipitation [104; 105]. The resultant changes in porosity and permeability due to chemical reaction and salt precipitation were also considered. We accounted for two cycles of relative permeability hysteresis (primary and secondary drainage and imbibition) by applying two di®erent trapping models: Land (1968) [69] and Spiteri et al.(2005) [103]. Therefore, relative permeability changes and variations in the trapped non-wetting phase saturations due to hysteresis can be updated on a block-by-block basis. We then used this streamline-based simulator to design CO2 storage in aquifers. We propose a carbon storage strategy where CO2 and brine are injected into an aquifer together followed by brine injection alone. This renders 80-95% of the CO2 immobile in pore-scale (10s ¹m) droplets within the porous rock; over thousands to billions of years the CO2 may dissolve or precipitate as carbonate, but it will not migrate upwards and so is e®ectively sequestered. The CO2 is trapped during the decades-long lifetime of the injection phase, reducing the need for extensive monitoring for centuries. The method does not rely on an impermeable cap rock to contain the CO2; this is only a secondary containment for the small amount of remaining mobile gas. Furthermore, the favorable mobility ratio between injected and displaced fluids leads to a more uniform sweep of the aquifer leading to a higher storage e±ciency than injecting CO2 alone. This design was demonstrated through one-dimensional simulations that were verified through comparison with analytical solutions. We then performed simulations of CO2 storage in a North Sea aquifer. We design injection to give optimal storage e±ciency and to minimise the amount of water injected; for the case we study, injecting CO2 with a fractional flow between 85 and 100% followed by a short period of chase brine injection to give the best performance. Sensitivity studies were conducted for different rock wettabilities and comparison with the Land trapping model. We found that the effectiveness of our proposed strategy is very sensitive to the estimated residual CO2-phase trapping. We then extended our study of the design of CO2 storage in aquifers to oilfields. We again constructed analytical solutions to the transport equations accounting for relative permeability hysteresis. We used this to design an injection strategy where CO2 and brine are injected simultaneously followed by chase brine injection. We studied field- scale oil production and CO2 storage for di®erent CO2 volumetric fractional flowrates. While injecting at the optimum WAG ratio gives the fastest oil recovery, this allows CO2 to channel through the reservoir, leading to rapid CO2 breakthrough and extensive recycling of the gas. We propose to inject more water than optimum. This causes the CO2 to remain in the reservoir, increases the field life and leads to improved storage of CO2 as a trapped phase. Again, a short period of chase brine injection at the end of the process traps most of the remaining CO2. Finally, we investigated the e®ect of salt (halite) precipitation during dry, supercritical CO2 injection using our modifed streamline-based simulator. In this study, pseudo one- dimensional and two-dimensional homogeneous and heterogeneous systems were used to study the sensitivity of di®erent parameters, which include relative permeability, grid size and brine salinity to salt precipitation. In our three-dimensional model, based on a geological model of a CO2 injection site, we constructed a near wellbore fine grid model with almost 1.5 million grid cells. Simulations were conducted successfully, and we found that salt precipitation can be a very important e®ect to consider when dry CO2 is injected into a high salinity reservoir. In this reservoir, after only 2 years of CO2 injection, about 20% of permeability of the reservoir was reduced, which will seriously reduce the injectivity of the injector and fluid flow within the reservoir.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1998.
Includes bibliographical references (leaves 185-201).
Many industrially important synthesis reactions are carried out in liquid solvents such as aromatic compounds, chlorinated hydrocarbons, and other organic liquids which pose environmental and health hazards either because of their toxicity or their persistence in the environment. Hence proper disposal of these solvents and the prevention of accidental releases or routine emissions cause serious difficulties and costs for the industries who use them. An approach to mitigating these problems is to use alternative solvents that are environmentally benign or that can be completely recycled in a closed-loop process. One such alternative solvent is supercritical carbon dioxide. Although supercritical carbon dioxide is used in many industrial extraction and chromatography processes it is not widely used as a reaction medium and its effects on chemical reactions are not well understood. The goals of this research were to gain a better understanding as to the effect of supercritical carbon dioxide through a systematic investigation of solvent conditions on the rates and selectivities of several model organic synthesis reactions. In addition, the use of environmentally benign catalysts/promoters in gaseous and supercritical carbon dioxide as well as developing chemical pathways in which carbon dioxide can act as a solvent as well as a reactant were explored to expand the possible industrial applications. In the pursuit of these goals, new reactors, feed and sampling procedures, as well as new chemical pathways were explored. Specifically, the bimolecular rate constants of the Diets-Alder reaction of ethyl acrylate and cyclopentadiene were measured in supercritical carbon dioxide from 38 to 88 °C and pressures from 80 to 210 bar. At constant temperature, the rate increased with pressure or density and was most dramatic near the critical point of carbon dioxide. A traditional Arrhenius expression was used to correlate the kinetic data at a constant system density. All of the rate constant data were normalized to the rate constant at the same temperature and at a fixed density of 0.5 g/cm3. These normalized rate constants over a range of temperatures then collapsed on a single line as a function of density. Rates could be predicted using a bimolecular Arrhenius expression with the pre-exponential term having a linear dependence on density. Theoretically, a rigorous transition state theory rate constant was derived and used to gain a better understanding of the non-ideal solvent-reactant-product interactions which could influence the rate. Effects of pressure/density and temperature on the regio- and stereo- selectivity of several Diels-Alder reactions were explored. Regioselectivity did not correlate well with density changes; however, stereoselectivity did. As pressure was increased, the endo isomer always increased in the supercritical region. The stereoselectivity changes were modeled using temperature and density as the model inputs. Again, the rigorous transition state theory rate constant was used to explain the observed selectivity changes. Phase behavior played an important role in these investigations, sometimes influencing selectivity. The design and construction of reactors with a sapphire window allowed for visual access into the reaction environment to monitor phase behavior. Silica was shown to increase the rate and selectivity of several Diels-Alder reactions in carbon dioxide. Pressure/density effects were explored using the reaction of methyl vinyl ketone and penta-1,3-diene. Pressure did not affect the selectivity; however, it had a large effect on the yield of the reaction. This was discovered to be caused by the change in phase partitioning of the reactants between the fluid phase and the solid surface as pressure was changed. Adsorption isotherms at various pressures and temperatures were found. Because of the non-ideal system, the thermodynamic effect of temperature on the adsorption equilibrium needed to be derived. The effect of temperature on the adsorption was found at constant pressure. Although an enthalpy of adsorption could be determined, the presence of non-ideal phase behavior complicates its interpretation. In general, the adsorption enthalpy consists of partial molar enthalpies of both species (reactant and carbon dioxide) on/in both phases (solid/fluid). At constant density, the effect of temperature allows for the direct calculation of the entropy of adsorption. This term is affected by the partial molar entropies of both species on/in both phases. Three different carboxylation reactions were investigated in supercritical carbon dioxide. The Kolbe-Schmitt reaction (direct carboxylation of a phenolate salt) was found to proceed at high yields in supercritical carbon dioxide. Attempts at lowering the temperature of reaction by using cosolvents was not successful. Temperature and pressure had minimal effect on the selectivity of the reaction. Two other carboxylation reactions were examined. In the first study, the homogeneous catalyzed caboxylation of an allylsilane was performed in supercritical carbon dioxide. Pressure did not appear to affect the reaction; however, there was a narrow temperature range which allowed the reaction to proceed. At best, yields were only 15%. The final reaction studied was the catalyzed (Lewis acid) carboxylation of an alkene by carbon dioxide. Unfortunately it did not proceed in supercritical carbon dioxide to any measurable extent at temperatures of 40 to 350 °C with and without the presence of various catalysts.
by Randy D. Weinstein.
Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Engineering Systems Division, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
This research examines the liability of storing CO2 in geological formations. There is a potential tortious and contractual liability exposure if stored CO2 is not fully contained by the geological formation. Using a combination of case study and survey methods, this research examines the risks confronted by CO2 storage, the legal and regulatory regimes governing these risks, and liability arrangements in other sectors where analogous risks have been confronted. Currently identifiable sources of liability include induced seismicity, groundwater contamination, harm to human health and the environment, property interests, and permanence. The risks of CO2 storage are analyzed in the context of several case studies: acid gas injection, natural gas storage, secondary oil recovery, and enhanced oil recovery. Methods for containing liability are considered in the context of regulatory analogs. This research finds that the current public and private mechanisms that would govern CO2 storage liability do not adequately address the issue. The analysis reveals six lessons learned: (1) the successful resolution of the CO2 liability issue will require combining our understanding of physical and regulatory analogs; (2) the prospect of CO2 storage liability will affect the implementation of predictive models and incentives to monitor leakage; (3) jurisdictional differences in liability exposure could affect where storage projects are eventually sited; (4) the development of liability rules is a function of an industry's emergence, but an industry's emergence, in turn, may affect the content of the liability rules; (5) regulatory compliance is not always a safe harbor for liability; and (6) statutes of limitation and repose mean that private liability is not necessarily "forever". A new liability arrangement is advocated where the current permitting regime is amended, long-term liability is managed by a governmental CO2 Storage Corporation with backing from an industry-financed CO2 Storage Fund, compensation for tortious liability occurs through an Office of Special Masters for CO2 Storage in the U.S. Federal Court of Claims, and the permanence issue is addressed on an annual ex post basis during the injection phase of CO2 storage operations and on an ex ante basis when sites are transferred to the CO2 Storage Corporation.
by Mark Anthony de Figueiredo.
Ph.D.