No description available.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-11-26T11:03:21Z No. of bitstreams: 1 diss_final_Barbara_pgetema.pdf: 1961642 bytes, checksum: e697bce70379b05d18b7de59fe7b4784 (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-11-27T16:37:44Z (GMT) No. of bitstreams: 1 diss_final_Barbara_pgetema.pdf: 1961642 bytes, checksum: e697bce70379b05d18b7de59fe7b4784 (MD5) / Made available in DSpace on 2018-11-27T16:43:10Z (GMT). No. of bitstreams: 1 diss_final_Barbara_pgetema.pdf: 1961642 bytes, checksum: e697bce70379b05d18b7de59fe7b4784 (MD5) Previous issue date: 2018-07-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / An efficient and low-cost strategy in the search for processes for the separation of CO2 from the natural gas is the physical immobilization of the ionic liquids (ILs) in solid materials. Mesoporous silicas are interesting materials to be used as supports because they have high surface area and pore volume. Besides that, the ionic liquids have been studied and appointed as a potential substitute for the commercial solvents, due to their characteristics and the possibility of combining a selection of anions and cations. In this case, anions having direct interference in the sorption capacity. In this context, the objective of this study was to evaluate the effect of the physical immobilization of two ionic liquids with different anions (bmim [Cl] and bmim [OAc]) on two mesoporous supports (commercial silica SBA-15 and silica extracted from rice husk) for the separation of CO2 from the natural gas through the experimental determination of CO2 sorption, selectivity (CO2/CH4) and sorption kinetics. The results have shown that pure solid supports have the greatest sorption capacity of CO2 when compared to immobilized. However, the CO2 removal efficiency in the CO2/CH4 mixture of the immobilized supports (evaluated by the selectivity) improves considerably. The best selectivity results were obtained for supports immobilized with the IL bmim[Cl] and the contribuition of SIL-Cl (3.03 ? 0.12) to separation performance (CO2/CH4) is similar to SBA-Cl (3.29 ? 0.39). The materials supported with ionic liquids have also presented fastest sorption kinetics when compared to the pure ILs. Also, the SIL-Cl was the most interesting combination of support and ionic liquid, when considering these parameters and the cost. / Uma estrat?gia interessante na busca de processos para separa??o de CO2 do g?s natural mais eficiente e de baixo custo ? a imobiliza??o f?sica de l?quidos i?nicos (LIs) em materiais s?lidos. As s?licas mesoporosas s?o materiais interessantes para a utiliza??o como suportes, pois apresentam grande ?rea superficial e volume de poros, j? os l?quidos i?nicos v?m sendo estudados e apontados como potencial substituinte aos solventes comerciais, devido a suas caracter?sticas e possibilidade de combina??o atrav?s da escolha de c?tions e ?nions, sendo que os ?nions t?m interfer?ncia direta na capacidade de sor??o. Neste contexto, o objetivo deste trabalho foi avaliar o efeito da imobiliza??o f?sica de dois l?quidos i?nicos com ?nions diferentes (bmim[Cl] e bmim[OAc]) em dois suportes mesoporosos (s?lica comercial SBA-15 e s?lica extra?da da casca de arroz) para separa??o de CO2 do g?s natural atrav?s da determina??o experimental da sor??o de CO2, seletividade (CO2/CH4) e cin?tica de sor??o. Os resultados mostraram que os suportes s?lidos puros tem a maior capacidade de sor??o do CO2 quando comparados com os imobilizados, entretanto a efici?ncia de remo??o do CO2 na mistura CO2/CH4 (avaliada pela seletividade) dos suportes imobilizados melhora consideravelmente. Os melhores resultados de seletividade foram obtidos com os suportes imobilizados com o LI bmim[Cl] e a contribui??o de SIL-Cl (3,03 ? 0,12) para a separa??o (CO2/CH4) foi similar a SBA-Cl (3,29 ? 0,39). Os materiais suportados com l?quidos i?nicos tamb?m apresentaram cin?tica de sor??o r?pida quando comparados com os LIs puros, sendo SIL-Cl a combina??o mais interessante de suporte e l?quido i?nico, considerando estes par?metros e o custo.

Submitted by PPG Engenharia e Tecnologia de Materiais (engenharia.pg.materiais@pucrs.br) on 2018-11-28T12:43:18Z No. of bitstreams: 1 diss_final_Barbara_pgetema.pdf: 1961642 bytes, checksum: e697bce70379b05d18b7de59fe7b4784 (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-11-29T10:34:05Z (GMT) No. of bitstreams: 1 diss_final_Barbara_pgetema.pdf: 1961642 bytes, checksum: e697bce70379b05d18b7de59fe7b4784 (MD5) / Made available in DSpace on 2018-11-29T10:54:06Z (GMT). No. of bitstreams: 1 diss_final_Barbara_pgetema.pdf: 1961642 bytes, checksum: e697bce70379b05d18b7de59fe7b4784 (MD5) Previous issue date: 2018-07-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / An efficient and low-cost strategy in the search for processes for the separation of CO2 from the natural gas is the physical immobilization of the ionic liquids (ILs) in solid materials. Mesoporous silicas are interesting materials to be used as supports because they have high surface area and pore volume. Besides that, the ionic liquids have been studied and appointed as a potential substitute for the commercial solvents, due to their characteristics and the possibility of combining a selection of anions and cations. In this case, anions having direct interference in the sorption capacity. In this context, the objective of this study was to evaluate the effect of the physical immobilization of two ionic liquids with different anions (bmim [Cl] and bmim [OAc]) on two mesoporous supports (commercial silica SBA-15 and silica extracted from rice husk) for the separation of CO2 from the natural gas through the experimental determination of CO2 sorption, selectivity (CO2/CH4) and sorption kinetics. The results have shown that pure solid supports have the greatest sorption capacity of CO2 when compared to immobilized. However, the CO2 removal efficiency in the CO2/CH4 mixture of the immobilized supports (evaluated by the selectivity) improves considerably. The best selectivity results were obtained for supports immobilized with the IL bmim[Cl] and the contribuition of SIL-Cl (3.03 ? 0.12) to separation performance (CO2/CH4) is similar to SBA-Cl (3.29 ? 0.39). The materials supported with ionic liquids have also presented fastest sorption kinetics when compared to the pure ILs. Also, the SIL-Cl was the most interesting combination of support and ionic liquid, when considering these parameters and the cost. / Uma estrat?gia interessante na busca de processos para separa??o de CO2 do g?s natural mais eficiente e de baixo custo ? a imobiliza??o f?sica de l?quidos i?nicos (LIs) em materiais s?lidos. As s?licas mesoporosas s?o materiais interessantes para a utiliza??o como suportes, pois apresentam grande ?rea superficial e volume de poros, j? os l?quidos i?nicos v?m sendo estudados e apontados como potencial substituinte aos solventes comerciais, devido a suas caracter?sticas e possibilidade de combina??o atrav?s da escolha de c?tions e ?nions, sendo que os ?nions t?m interfer?ncia direta na capacidade de sor??o. Neste contexto, o objetivo deste trabalho foi avaliar o efeito da imobiliza??o f?sica de dois l?quidos i?nicos com ?nions diferentes (bmim[Cl] e bmim[OAc]) em dois suportes mesoporosos (s?lica comercial SBA-15 e s?lica extra?da da casca de arroz) para separa??o de CO2 do g?s natural atrav?s da determina??o experimental da sor??o de CO2, seletividade (CO2/CH4) e cin?tica de sor??o. Os resultados mostraram que os suportes s?lidos puros tem a maior capacidade de sor??o do CO2 quando comparados com os imobilizados, entretanto a efici?ncia de remo??o do CO2 na mistura CO2/CH4 (avaliada pela seletividade) dos suportes imobilizados melhora consideravelmente. Os melhores resultados de seletividade foram obtidos com os suportes imobilizados com o LI bmim[Cl] e a contribui??o de SIL-Cl (3,03 ? 0,12) para a separa??o (CO2/CH4) foi similar a SBA-Cl (3,29 ? 0,39). Os materiais suportados com l?quidos i?nicos tamb?m apresentaram cin?tica de sor??o r?pida quando comparados com os LIs puros, sendo SIL-Cl a combina??o mais interessante de suporte e l?quido i?nico, considerando estes par?metros e o custo.

Hydrothermally treated biomass could not only be used as a fuel or a fertilizer but it can also be refined into high-value products. Activated carbons are one of those. In the studies of this thesis, four different hydrothermally carbonized (HTC) biomasses, including horse manure, grass cuttings, beer waste and biosludge, have been successfully made into activated carbons. The activated carbon materials were in the forms of powdered activated carbons, powdered composites of activated carbon and iron oxide nano-crystals, and activated carbon discs. The HTC biomasses and the activated carbons were characterized and analyzed using several methods. The biomasses were carbonized to different extent during the hydrothermal treatment, which depended on the different natures of the biomasses. The HTC biomasses were activated into powdered activated carbons by both physical activation, using CO2, and by chemical activation, using H3PO4. Full factorial design matrices were applied to design experiments and study the influence of different parameters used during both physical and chemical activation. Activated carbons with embedded iron oxide nanoparticles were synthesized through hydrothermal carbonization followed by CO2 activation. These composites had high surface areas and showed a strong magnetism, and the powders could be separated from liquid phase by applying a magnetic field. Strong and dense activated carbon discs were also prepared from powdered HTC beer waste by pulsed current processing (PCP) and a subsequent CO2 activation procedure. The potential for carbon dioxide separation from nitrogen, and methylene blue adsorption in aqueous solution, were assessed for the powdered activated carbons produced from HTC biomasses. They showed good performance in both applications. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 1: In press.</p>

No description available.

Global CO2 emissions produced by energy-related processes, mainly power plants, have increased rapidly in recent decades; and are widely accepted as the dominant contributor to the greenhouse gas (GHG) effect and consequent climate changes. Among countermeasures against the emissions, CO2 capture and storage (CCS) is receiving much attention. Capture of CO2 is the core step of CCS as it contributes around 75% of the overall cost, and may increase the production costs of electricity by over 50%. The reduction in capture costs is one of the most challenging issues in application of CCS to the energy industry. Using limestone in CaO-looping cycles is a promising capture technology to provide a cost-effective separation process to remove CO2 content from power plants operations. Limestone has the advantage of being relatively abundant and cheap, and that has already been widely used as a sorbent for sulphur capture. However, this technology suffers from a critical challenge caused by the decay in the sorbent capture capacity during cyclic carbonation/calcination, which results in the need for more sorbent make-up; hence a reduction in cost efficiency of the technology. The performance of sorbent influenced by several operating and reaction conditions. Therefore, much research involves investigation of influencing factors and different methods to reduce the sorbent deactivation. Cont/d.

A necessidade atual do mercado brasileiro para aumentar a oferta de gás incentiva a comunidade científica nacional no desafio de desenvolvimento de novas rotas tecnológicas, visando aumentar o aproveitamento do gás natural. Tal desafio é acompanhado por uma demanda mundial dos países signatários do Protocolo de Quioto (ratificado em 2005) para a redução das emissões de gases de efeito estufa. Apesar de o Brasil não apresentar nenhuma meta de redução, no primeiro período deste Protocolo (2008 a 2012), o setor do petróleo (atividade de E&P), através de suas companhias operadoras, que atuam no país, já estabeleceram metas corporativas para emissão evitada de gases de efeito estufa, em suas instalações de produção (maior predominância das unidades marítimas de produção). O presente trabalho aborda a análise técnica e econômica de um processo proposto de separação e captura de dióxido de carbono (CO2), através de estudo de caso (Primeira e Segunda Proposição) de simulação de processo, em uma instalação marítima de produção de petróleo, comparativamente a sua ausência (Caso Base). A Primeira Proposição considera a separação e a captura do CO2 oriundo tanto do gás natural produzido, quanto do gás de queima de uma turbina a gás. A Segunda Proposição considera a separação e a captura do CO2 oriundo somente do gás natural produzido. Até o momento, no Brasil, ainda não foram desenvolvidas tecnologias adequadas para a captura do CO2, em instalações marítimas de produção de petróleo. Adicionalmente a regulação atual (Portaria nº104/2002 da ANP) limita o potencial de utilização do CO2 que existe na composição do gás natural comercializado no país, pelo fato de não diferenciar em sua especificação técnica, os usos deste importante combustível. Os resultados obtidos nesta tese, com a utilização de simulador de processo de uso comercial mostraram emissões evitadas de CO2 para atmosfera de 55 % (caso Segunda Proposição que apresentou maior viabilidade econômica), em relação ao resultado obtido para o Caso Base. Este relevante resultado equivale a uma emissão evitada de aproximadamente 241 x 103 t/ano, para uma única unidade piloto proposta. De acordo com o estudo de análise econômica apresentado, a Segunda Proposição (VPL US$ 15,3 x 106) foi melhor do que a da Primeira Proposição (VPL: US$ 13,9 x 106) ambos usando o Caso Base como referência. Dentre os ganhos esperados com o uso desta nova tecnologia destacam-se: redução do consumo interno e das perdas de gás natural, emissão evitada de CO2 e hidrocarbonetos para a atmosfera, além do aumento das práticas de armazenamento de gás e CO2, em reservatórios geológicos depletados de petróleo. Estima-se que num cenário futuro, com a implantação deste novo processo proposto, em instalações marítimas de produção de petróleo, uma relevante contribuição de emissões evitadas de gases de efeito estufa possa ocorrer na área de E&P de petróleo no Brasil. / The current Brazilian market needs to increase the natural gas supply to incentive the national scientific community to the challenge of developing new technologies routes aiming increase the utilization of the produced natural gas. Such challenge is followed by a world demand from signatory countries of the Kyoto Agreement (ratified in 2005) to reduce the greenhouse gas emissions. In spite of, the Brazil does not have any reduction goal, in the first period (2008 to 2012) the oil sector (E&P activity), by their oil operators companies that works in our country, has already established corporative goals to avoided greenhouse gas emissions in their production facilities (bigger predominance of offshore production unities). The present work approaches the economic and technical evaluation of a carbon dioxide (CO2) separation and capture proposal process (First and Second Proposal Case) comparatively your absence (Base Case). The First Case consider the CO2 separation and capture both the produced gas and exhausted gases of one turbine driven by gas. The Second Case consider only the CO2 separation and capture from the produced gas. At the present, in Brazil, it has not been developed yet suitable technologies, for such use, and the CO2 is normally disposal to the atmosphere. Moreover, the present Regulation (104/2002 ANP Decree) limit the potential of CO2 use existing in the gas composition that is marketed in the country, due to not differentiate the uses of this important fuel. The results obtained of this thesis, by using a process simulator of commercially use showed CO2 avoided emissions of 55 % to the atmosphere (Second Proposal Case that shows the best economic evaluation) related to the result obtained from the Base Case. This relevant result is equivalent in mass flow, to the avoidance emission of roughly 241 x 103 tons per year, for a single pilot unity proposal. According the economic evaluation study, the Second Proposal Case (VPL:US$ 15,3 x 106) was better than the First Case (VPL: US$ 13,9 x 106), using the Case Base as reference. Within the benefits expected with the use of this new technology are the following: reduction both the internal gas consumption and natural gas losses (atmospheric disposal), emissions avoided of CO2 and hydrocarbons, beyond the increase of CO2 and gas storage practices in offshore depleted oil fields. It is estimated, in future scenery, with the implantation of this new proposal process in offshore production unities, relevant contribution of avoided greenhouse gases emissions can occur in oil E&P tasks in Brazil.

A necessidade atual do mercado brasileiro para aumentar a oferta de gás incentiva a comunidade científica nacional no desafio de desenvolvimento de novas rotas tecnológicas, visando aumentar o aproveitamento do gás natural. Tal desafio é acompanhado por uma demanda mundial dos países signatários do Protocolo de Quioto (ratificado em 2005) para a redução das emissões de gases de efeito estufa. Apesar de o Brasil não apresentar nenhuma meta de redução, no primeiro período deste Protocolo (2008 a 2012), o setor do petróleo (atividade de E&P), através de suas companhias operadoras, que atuam no país, já estabeleceram metas corporativas para emissão evitada de gases de efeito estufa, em suas instalações de produção (maior predominância das unidades marítimas de produção). O presente trabalho aborda a análise técnica e econômica de um processo proposto de separação e captura de dióxido de carbono (CO2), através de estudo de caso (Primeira e Segunda Proposição) de simulação de processo, em uma instalação marítima de produção de petróleo, comparativamente a sua ausência (Caso Base). A Primeira Proposição considera a separação e a captura do CO2 oriundo tanto do gás natural produzido, quanto do gás de queima de uma turbina a gás. A Segunda Proposição considera a separação e a captura do CO2 oriundo somente do gás natural produzido. Até o momento, no Brasil, ainda não foram desenvolvidas tecnologias adequadas para a captura do CO2, em instalações marítimas de produção de petróleo. Adicionalmente a regulação atual (Portaria nº104/2002 da ANP) limita o potencial de utilização do CO2 que existe na composição do gás natural comercializado no país, pelo fato de não diferenciar em sua especificação técnica, os usos deste importante combustível. Os resultados obtidos nesta tese, com a utilização de simulador de processo de uso comercial mostraram emissões evitadas de CO2 para atmosfera de 55 % (caso Segunda Proposição que apresentou maior viabilidade econômica), em relação ao resultado obtido para o Caso Base. Este relevante resultado equivale a uma emissão evitada de aproximadamente 241 x 103 t/ano, para uma única unidade piloto proposta. De acordo com o estudo de análise econômica apresentado, a Segunda Proposição (VPL US$ 15,3 x 106) foi melhor do que a da Primeira Proposição (VPL: US$ 13,9 x 106) ambos usando o Caso Base como referência. Dentre os ganhos esperados com o uso desta nova tecnologia destacam-se: redução do consumo interno e das perdas de gás natural, emissão evitada de CO2 e hidrocarbonetos para a atmosfera, além do aumento das práticas de armazenamento de gás e CO2, em reservatórios geológicos depletados de petróleo. Estima-se que num cenário futuro, com a implantação deste novo processo proposto, em instalações marítimas de produção de petróleo, uma relevante contribuição de emissões evitadas de gases de efeito estufa possa ocorrer na área de E&P de petróleo no Brasil. / The current Brazilian market needs to increase the natural gas supply to incentive the national scientific community to the challenge of developing new technologies routes aiming increase the utilization of the produced natural gas. Such challenge is followed by a world demand from signatory countries of the Kyoto Agreement (ratified in 2005) to reduce the greenhouse gas emissions. In spite of, the Brazil does not have any reduction goal, in the first period (2008 to 2012) the oil sector (E&P activity), by their oil operators companies that works in our country, has already established corporative goals to avoided greenhouse gas emissions in their production facilities (bigger predominance of offshore production unities). The present work approaches the economic and technical evaluation of a carbon dioxide (CO2) separation and capture proposal process (First and Second Proposal Case) comparatively your absence (Base Case). The First Case consider the CO2 separation and capture both the produced gas and exhausted gases of one turbine driven by gas. The Second Case consider only the CO2 separation and capture from the produced gas. At the present, in Brazil, it has not been developed yet suitable technologies, for such use, and the CO2 is normally disposal to the atmosphere. Moreover, the present Regulation (104/2002 ANP Decree) limit the potential of CO2 use existing in the gas composition that is marketed in the country, due to not differentiate the uses of this important fuel. The results obtained of this thesis, by using a process simulator of commercially use showed CO2 avoided emissions of 55 % to the atmosphere (Second Proposal Case that shows the best economic evaluation) related to the result obtained from the Base Case. This relevant result is equivalent in mass flow, to the avoidance emission of roughly 241 x 103 tons per year, for a single pilot unity proposal. According the economic evaluation study, the Second Proposal Case (VPL:US$ 15,3 x 106) was better than the First Case (VPL: US$ 13,9 x 106), using the Case Base as reference. Within the benefits expected with the use of this new technology are the following: reduction both the internal gas consumption and natural gas losses (atmospheric disposal), emissions avoided of CO2 and hydrocarbons, beyond the increase of CO2 and gas storage practices in offshore depleted oil fields. It is estimated, in future scenery, with the implantation of this new proposal process in offshore production unities, relevant contribution of avoided greenhouse gases emissions can occur in oil E&P tasks in Brazil.

Molten Carbonate Fuel cells are high temperature fuel cells suitable for distributed generation and combined heat and power, and are today being installed on commercial basis in sizes from 100kW to several MW. Novel applications for MCFC which have attracted interest lately are MCFC used for CO2 separation from combustion flue gas, and high temperature electrolysis with reversible fuel cells. In the first application, the intrinsic capability of the MCFC to concentrate CO2 from the cathode to the anode side through the cell reaction is utilized. In the second application, the high operating temperature and relatively simple design of the MCFC is utilized in electrolysis, with the aim to produce a syngas mix which can be further processed into hydrogen of synthetic fuels. In this thesis, the effect on fuel cell performance of operating a small lab-scale molten carbonate fuel cell in conditions which simulate those that would apply if the fuel cell was used for CO2 separation in combustion flue gas was studied. Such operating conditions are characterized especially by a low CO2 concentration at the cathode compared to normal operating conditions. Sulfur contaminants in fuel gas, especially H2S, are known poisoning agents which cause premature degradation of the MCFC. Furthermore, combustion flue gas often contains sulfur dioxide which, if entering the cathode, causes performance degradation by corrosion and by poisoning of the fuel cell. This makes poisoning by sulfur contaminants of great concern for MCFC development. In this thesis, the effect of sulfur contaminants at both anode and cathode on fuel cell degradation was evaluated in both normal and in low CO2 simulated flue gas conditions.      The results suggested that the poisoning effect of SO2 at the cathode is similar to that of H2S at the anode, and that it is possibly due to a transfer of sulfur from cathode to anode. Furthermore, in combination with low CO2 conditions at the cathode, SO2 contaminants cause fuel cell poisoning and electrolyte degradation, causing high internal resistance. By using a small lab-scale MCFC with commercial materials and standard fuel cell operating conditions, the reversible MCFC was demonstrated to be feasible. The electrochemical performance was investigated in both fuel cell (MCFC) and electrolysis cell (MCEC) modes. The separate electrodes were studied in fuel cell and electrolysis modes under different operating conditions. It was shown that the fuel cell exhibited lower polarization in MCEC mode than in MCFC mode, and a high CO2 concentration at the fuel cell anode reduced the polarization in electrolysis mode, which suggested that CO2 is reduced to produce CO or carbonate. / Smältkarbonatbränsleceller (MCFC) är en typ av högtemperaturbränsleceller som är anpassade för kombinerad el- och värmeproduktion i mellan-till stor skala. Idag installeras MCFC på kommersiell basis i storlekar mellan 100kW och flera MW. En ny typ av tillämpning för MCFC som har väckt intresse på senare tid är användandet av MCFC för CO2-avskiljning i kombination med konventionell elproduktion genom förbränning. En annan ny tillämpning är högtemperaturelektrolys genom användandet av reversibla bränsleceller. I det första fallet utnyttjas att CO2 kan koncentreras från katod- till anodsidan, vilket sker genom cellreaktionen för MCFC. I det andra fallet utnyttjas den höga arbetstemperaturen och den relativt enkla cell-designen för att använda reversibla MCFC till elektrolys, med syfte att producera en syngas-blandning som kan förädlas till vätgas eller till syntetiskt bränsle. I denna avhandling studeras effekten på bränslecellens prestanda genom att operera en MCFC i lab-skala med driftförhållanden som simulerar de som förväntas uppkomma om bränslecellen användes för CO2-avskiljning ur rökgaser från förbränning. Dessa driftförhållanden karaktäriseras av låg CO2-koncentration på katodsidan jämfört med normal drift. Svavelföroreningar i bränsle, speciellt H2S, är kända för att orsaka förgiftning av anoden, vilket i sin tur försämrar bränslecellens prestanda. Dessutom innehåller rökgaser ofta SO2, vilket antas orsaka korrosion och förgiftning av katoden. Detta gör effekten av svavelföroreningar till ett prioriterat ämne för utvecklingen av MCFC. I denna avhandling undersöks effekten av svavelföroreningar på både anod- och katodsidan, i normala driftförhållanden och i förhållanden med låg CO2 som simulerar användandet av rökgaser för CO2-avskiljning. Resultaten tyder på att effekten av förgiftning med SO2 på katoden liknar den med H2S på anoden, och att detta kan vara orsakat av en transport av svavel från katod till anod. Vidare, i kombination med låg CO2 koncentration på katoden så orsakar SO2-föroreningar elektrolytdegradering, vilket orsakar hög inre resistans. Genom att använda en liten MCFC i lab-skala med kommersiella material och standardförhållanden för MCFC påvisades att reversibla smältkarbonatbränsleceller kan vara ett lovande koncept. Den elektrokemiska prestandan av både cell och separata elektroder undersöktes både som bränslecell (MCFC)och vid elektrolys (MCEC). Resultaten visade att cellen uppvisade lägre polarisation vid elektrolys än som bränslecell, och att ten hög CO2-koncentration på det som är bränslecellens anodsida gav upphov till en minskad elektrodpolarisation, vilket indikerar att CO2 reduceras för att producera CO eller karbonat. / <p>QC 20141028</p>

LTA-type zeolites with narrow window apertures coinciding with the approximate size of small gaseous molecules such as CO2 and N2 are interesting candidates for adsorbents with swing adsorption technologies due to their molecular sieving capabilities and otherwise attractive properties. These sieving capabilities are dependent on the energy barriers of diffusion between the zeolite pores, which can be fine-tuned by altering the framework composition. An ab initio level of theory is necessary to accurately describe specific gas-zeolite interaction and diffusion properties, while it is desirable to predict the macroscopic scale diffusion for industrial applications. Hence, a multiscale modeling approach is necessary to describe the molecular sieving phenomena exhaustively. In this thesis, we use several different modeling methods on different length and time scales to describe the diffusion driven uptake and separation of CO2 and N2 in Zeolite NaKA. A combination of classical force field based modeling methods are used to show the importance of taking into account both thermodynamic, as well as, kinetic effects when modeling gas uptake in narrow pore zeolites where the gas diffusion is to some extent hindered. For a more detailed investigation of the gas molecules’ pore-to-pore dynamics in the material, we present a procedure to compute the free energy barriers of diffusion using spatially constrained ab initio Molecular Dynamics. With this procedure, we seek to identify diffusion rate determining local properties of the Zeolite NaKA pores, including the Na+-to-K+ exchange at different ion sites and the presence of additional CO2 molecules in the pores. This energy barrier information is then used as input for the Kinetic Monte Carlo method, allowing us to simulate and compare these and other effects on the diffusion driven uptake using a realistic powder particle model on macroscopic timescales. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.</p>