Den stora oron för de ökade växthusutsläppen och klimatförändringas effekter har uppmuntrat utvecklingen av åtgärder för att motverka de negativa konsekvenserna. En av de tekniker som har uppmärksammats under de senaste decennierna är kolavskiljningstekniken. Men nuförtiden är kolavskiljning en teknik som är relaterad till höga kostnader där både kapital- och driftskostnaderna är höga. Därför utfördes i detta projekt ett försök att minska kostnaden genom att ersätta den absorptionspackade kolonnen med ett nytt kompakt system. I detta fall atomiserade det kompakta systemet lösningsmedlet till droppar för att öka massöverföringen av koldioxidabsorptionen. Syftet med detta projekt var att utföra en jämförande teknisk-ekonomisk utvärdering av den konventionella kemiska absorptionsprocessen med packade kolonner mot en process med ett kompakt system. En processmodell för den konventionella processen etablerades i Aspen Plus. Dessutom manipulerades den berikade lösningen i samma processmodell för att simulera den förbättrade absorptionen på grund av atomatiseringen av lösningsmedlet. Det resulterade i att implementeringen av det kompakta systemet kunde generera tekniska förbättringar som ett minskat användande av lösningsmedel och en lägre återkokningsbelastning i regenereringskolonnen. Det var dock ingen betydande minskning av den totala fångstkostnaden. I det här fallet var de främsta bidragande faktorerna till fångstkostnaden var kompressorkostnaden och det höga elpriset. Känslighetsanalysen visade dock i huvudsak att fångstkostnaden skulle kunna sänkas när elpriset är lägre. Man kan dra slutsatsen att kompakta system är en lovande teknik som skulle kunna bidra till utvecklingen av kolavskiljningstekniken. Framtida undersökningar av processdesignen krävs dock för att sänka fångstkostnaden ännu mer. / The great concern regarding the increased greenhouse emissions and the effects of the climate change has encouraged the development of solution in order to counteract the negative consequences. One of the technologies that has gained attention during the last decades has been the carbon capture technology. However, nowadays the carbon capture has been a technology that has been related to high capture costs where both capital and operational costs usually has been high. Therefore, in this project, an attempt was realized to reduce the capture cost by replacing the absorption packed column with a novel compact system. In this case, the compact system atomized the solvent into droplets in order to enhance the mass transfer of the carbon dioxide absorption. The aim of this project was to perform a comparative techno-economical evaluation of the conventional chemical absorption process with packed columns to a process with a compact system. A process model for the conventional process was established in Aspen Plus. Furthermore, the rich loading was varied in the same process model in order to simulate the enhanced absorption due to the atomization of the solvent. It resulted that the implementation of the compact system could generate technical benefits such as a reduced solvent utilization and a lower reboiler duty in the stripper column. However, there was no significant reduction regarding the total capture cost. In this case, the main contributors to the capture cost were the compressor cost and the high electricity price. Nevertheless, the sensitivity analysis showed principally that the capture cost could be reduced if the power required in the flue gas compressor can be reduced. It could be concluded that the compact system is a promising technology that could contribute to a further development of the carbon capture technology. However, future investigations regarding the process design are required in order reduce the capture cost even more.

As the world population keeps increasing, ammonia-based fertilizers like urea are essential to provide food security. However, the current fertilizer industry is based on fossil fuel feedstock (mainly natural gas), making the production process CO2 emission-intensive. More specifically, besides the CO2 emitted during the process, the CO2 captured in urea is also released into the atmosphere after the fertilizer is applied to agricultural soils. Thus, positioning the fertilizer industry among the top four industrial emitters globally. Hence, in order to meet the target of limiting global warming to 1.5 ºC and achieve net-zero emissions by 2050, it is necessary to strengthen the carbon mitigation efforts in the current fertilizer industry. This can be achieved in different ways, such as using renewable biofuels and implementing technologies that can lead to zero/negative CO2 emissions. For that reason, the present study presents pathways to achieve a more environmentally friendly fertilizer production process. An overall analysis is performed if negative emissions can be achieved by replacing different fractions of natural gas (used as both feedstock and fuel) with biogas and biomethane and by capturing and storing the CO2 emitted from the process using chemical solvents as activated MDEA and MEA. The results obtained from the study revealed that negative emissions in fertilizer plant can be achieved by retrofitting an existing ammonia plant with a MEA based CO2 capture system (with a carbon capture rate of 90%) for the SMR burner flue gas, and by introducing 50% of biogas in the feedstock (alongside Natural gas), and 75% of biogas in the SMR burner fuel (alongside Natural gas). This initial approach would result in net negative emissions from urea's production and application and require approximately 0.5 kg of biogas per kg of urea produced in this case. Furthermore, the equivalent energy intensity for the negative emission urea plant would be 0.32% and 3.37% lower compared to the fossil fuel-based case without/with CCS, respectively. Ultimately, it is even possible to produce approximately 6% more urea product by replacing a particular fraction of natural gas with biogas. The reason for this increased production is due to the surplus of carbon dioxide by the introduction of biogas. It can be used along with the ammonia product going to storage in the fossil fuel-based case, where there was not enough CO2 to keep the feedstock molar ratio at the urea plant's inlet.

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No description available.

Le réchauffement de la planète est une préoccupation mondiale à notre époque. Celui-ci peut s’expliquer en partie par les grandes émissions de CO2 dans l’atmosphère depuis le début de l’industrialisation. Parmi les plus grands émetteurs de CO2, il y a entre autres les véhicules motorisés, le chauffage au charbon et les raffineries de pétrole. Depuis quelques années, un processus commence à être utilisé pour réduire les émissions de CO2 atmosphérique. Ce processus est la capture du CO2 par des solvants aminés régénérables. Dans le cadre de ma recherche, des échantillons d’un solvant aminé qui ont subi un traitement de capture et de régénération du CO2 et qui ont passé différents temps dans ces processus ont été analysés pour déterminer les différents produits de dégradation de ce solvent. L’identification des produits de dégradation permet d’optimiser la méthode de capture du CO2 pour éviter leur production et donc garder son efficacité le plus longtemps possible. La chromatographie liquide couplée à la spectrométrie de masse (LC-MS) a été utilisée pour séparer et identifier les différents produits de dégradation. L’utilisation de la spectrométrie de masse à haute résolution (HRMS) a permis l’identification des formules chimiques les plus probables pour les produits de dégradation présents. L’ajout d’une cellule de collision à la HRMS a permis d’obtenir plus d’information par fragmentation sur les différents groupes fonctionnels et donc sur la structure des composés inconnus. Lorsque les structures possibles sont peu nombreuses pour une telle formule chimique, des étalons ont été utilisés pour comparer les spectres obtenus et confirmer les structures. Pour les composés ayant trop de possibilités de structures moléculaires, d’autres méthodes d’analyse ont été effectuées, telle la chromatographie gazeuse couplée à la spectrométrie de masse (GC-MS), la spectrométrie à mobilité ionique et la spectroscopie à résonnance magnétique nucléaire (NMR) suite à une collecte de fractions en chromatographie liquide. Au final, aucun nouveau produit de dégradation n’a pu être identifié avec une certitude de 100 %. Le niveau de confiance envers la structure proposée est par contre assez élevé pour certains d’entre eux, mais la difficulté d’obtention d’étalons rend l’identification assez exigeante. L’ensemble de ces travaux de mémoire a été réalisé dans le cadre d’un partenariat industriel. Une autre partie du projet était le développement d’une méthode pour détecter et quantifier deux N-nitrosamines à une concentration de 1 µg/L. La validation de la méthode pour la quantification des nitrosamines a également été effectuée. Les deux nitrosamines sont des résidus des processus de dégradation des amines du partenaire industriel et il est recommandé que leur concentration soit inférieure à 1 µg/L lors du rejet des eaux usées dans une étendue d’eau naturelle (US Environnemental Protection Agency). Il est donc important de les déterminer pour éviter de contaminer les cours d’eaux. La méthode développée utilise une extraction liquide sur support solide comme préparation d’échantillon ainsi qu’une méthode LC-MS pour la séparation et la quantification. La plus grande quantité retrouvée d’une des deux nitrosamines est de 7,30 µg/L, ce qui est légèrement au-dessus des recommandations. / Global warming is one of the most important concerns of this century. It can be associated in major part to CO2 emissions into the atmosphere since the beginning of industrialization. The major CO2 emitters are motorized vehicles, coal heating and oil refineries. Some years ago, a scrubbing process started being used to reduce atmospheric emissions of CO2 from coal burning plants. This process is known as CO2 capture by regenerable amine-based solvents. As part of this master’s research, samples from an amine-based solvent that was subjected to CO2 capture for different amounts of time during the capture regeneration process were analyzed to determine the various degradation products formed from the capture solvent. Identification of the degradation products and their kinetics of formation allow optimization of the CO2 capture method, ideally to avoid their formation and to maximize the efficiency of the capture process over a longer period of use. Liquid chromatography coupled to mass spectrometry (LC-MS) was used to initially select various degradation products present in reasonable abundance. The use of high resolution mass spectrometry (HRMS) allowed the identification of the most probable chemical formulas for the degradation products found in the capture solvent. Addition of a collision cell to HRMS provided more information on the different functional groups by MS fragmentation, and therefore more structural information on the unknown compounds. When there were a few possible structures for a single unknown compound, standards were used to compare the MS spectra obtained and confirm the structures. For the unknown compounds with too many plausible structures, additional analysis methods were used, like gas chromatography coupled to mass spectrometry (GC-MS), ionic mobility mass spectrometry and nuclear magnetic resonance (NMR) after fraction collection by preparative liquid chromatography. No degradation products were identified with 100 % certainty. The level of confidence towards proposed structures was quite high for some of the unknowns; however, the standards needed to confirm their identification were too costly to synthesize. This entire master’s project was carried out in collaboration with an industrial partner. A secondary part of this master’s project involved the development of a method to detect and quantify two N-nitrosamines at a concentration of 1 µg/L. Validation of the method for the quantification of the two N-nitrosamines was also carried out. The two analytes were residues of the degradation process of a different amine-based CO2 capture solvent where the recommended concentration of the residues should be under 1 µg/L when releasing the wastewater into environmental waters (US Environnemental Protection Agency). It is therefore important to determine these N-nitrosamines to avoid contamination of water bodies. The developed method used solid-supported liquid-liquid extraction (SLE) for sample preparation and LC-MS for separation and quantification. The highest amount of one of the two N-nitrosamines found in the samples supplied by the industrial partner was 7.30 µg/L, which was over the recommended level.

Nanoporous organic polymers, including hypercrosslinked polymers (HCPs), covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), and conjugated microporous polymers (CMPs) etc., are considered good candidates for potential gas storage and gas separation applications. Porosities and surface areas of a series of semirigid alternating copolymers, which contained tert-butyl carboxylate-functionalized stilbene or tert-butyl carboxylate-functionalized styrene, and maleic anhydride or tert-butyl carboxylate-functionalized phenyl maleimide, were investigated using nitrogen sorption/desorption isotherms at 77 K and molecular simulations. These alternating copolymers were found to have Brunauer-Emmett-Teller (BET) surface areas in the range of 20-40 m2/g. Surface areas of these alternating copolymers increased as the steric crowding of the polymer backbone increased, which was the result of introducing extra phenyl rings and/or N-phenyl substituent maleimide units. Surface areas were found to increase as the persistence length increased. A series of HCPs containing functionalized stilbene and N-substituted phenyl maleimide were synthesized via free radical suspension polymerization. The incorporation of these functionalized, chain stiffening, Tg enhancing comonomers raised the Tgs of precursor polymers before they were crosslinked. Surface areas of these HCPs, obtained from nitrogen adsorption/desorption isotherms at 77 K, were up to 1058 m2/g. However, the surface areas of these HCPs were systematically lower than the controls. The high rigidity of the polymer backbone, which was the result of incorporating Tg enhancing comonomer, likely affected the chain mobility of the precursor polymer, decreased the efficiency of post-crosslinking reactions, and thus resulted in lower surface areas. Amine-functionalized styrene/stilbene polymers were prepared via free radical polymerization or post-modification. Amine-containing silica-based sorbents were prepared using the impregnation method. Sorption of CO2 by these materials was tested using TGA and compared with control samples. Both high amine content and certain levels of surface area were found to be important for a sorbent to achieve high CO2 uptake. Highest CO2 uptake (12 wt%) under our testing condition in these materials was achieved by an amine-containing silica sorbent. / Ph. D.

In recent years, membrane gas absorption technology has been considered as one of the promising alternatives to conventional techniques for CO2 capture due to its favorable mass transfer performance. As a hybrid approach of chemical absorption and membrane separation, it exhibits a number of advantages, such as operational flexibility, compact structure, high surface-area-to-volume ratio, linear scale up, modularity and predictable performance. One of the main challenges of membrane gas absorption technology is the membrane wetting by absorbent over prolonged operating time, which may significantly decrease the mass transfer coefficients of the membrane module. In this thesis, the experimental was set up to investigate the dependency of CO2 removal efficiency and mass transfer rate on various operating parameters, such as the gas and liquid flow rates, absorbent type and concentration and volume fraction CO2 at the feed gas inlet. In addition, the simultaneous removal of SO2 and CO2 was investigated to evaluate the feasibility of simultaneous desulphurization and decarbonization in the same membrane contactor. During 14 days of continuous operation, it was observed that the CO2 mass transfer rate decreased significantly following the operating time, which was attributed to partial membrane wetting. To better understand the wetting mechanism of membrane pores during their prolonged contact with absorbents, immersion experiments for up to 90 days were carried out. Various membrane characterization methods were used to illustrate the wetting process before and after the membrane fibers were exposed to the absorbents. The characterization results showed that the absorbent molecules diffused into the polypropylene polymer during the contact with the membrane, resulting in the swelling of the membrane. In addition, the effects of operating parameters such as immersion time and absorbent type on the membrane wetting were investigated in detail. Finally, based on the analysis results, methods to smooth the membrane wetting were discussed. It was suggested that improving the hydrophobicity of polypropylene membrane by surface modification may be an effective way to improve the long-term operating performance of membrane contactors. Therefore, the polypropylene hollow fibers were modified by depositing a thin superhydrophobic coating on the membrane surface to improve their hydrophobicity. The mixture of cyclohexanone and methylethyl ketone was considered as the best non-solvent to achieve the fiber surface with good homogeneity and acceptably high hydrophobicity. In the long-period operation, the modified membrane contactor exhibited more stable and efficient performance than the untreated one. Hence, surface treatment provides a feasibility of improving the system stability for CO2 capture from the view of long-term operation. / En av de tekniker som under senare framhållits som ett lovande alternativ till konventionell CO2-avskiljning är membran-gas-absorptionstekniken på grund av god prestanda vad gäller masstransport. Det blandade angreppssättet med både kemisk absorption och membranseparation har en rad fördelar, såsom driftflexibilitet, kompakt konstruktion, högt yt-volymsförhållande, linjär uppskalning, modularitet och förutsägbar prestanda. En av de viktigaste utmaningarna för membran-gas-absorptionstekniken är vätningen av membranet med absorbenten under långa drifttider, vilket väsentligt kan minska membranmodulens masstransportkoefficienter.  I avhandlingen har en rad olika driftparametrars påverkan på CO2-reningsgraden och massöverföringshastigheten undersökts. Driftparametrar inkluderar gas- och vätskeflöden, typ av absorbent och koncentration och volymfraktion av CO2 vid gasinloppet. Avskiljning av SO2 och CO2 har dessutom undersökts för att utvärdera möjligheten att samtidigt, i samma membranenhet, avlägsna svavel och kol. Under 14 dagars kontinuerlig drift konstaterades det att massöverföringshastigheten för CO2 minskade avsevärt med drifttiden, vilket hänfördes till partiell vätning av membranet.   För att bättre förstå mekanismerna för vätning av membranporer under långvarig kontakt med absorbenter genomfördes doppningsexperiment i upp till 90 dagar. Olika metoder för karakterisering av membran användes för att illustrera vätningsprocessen före och efter det att membranfibrerna exponerades för absorbenterna. Resultaten av karakteriseringen visade att absorbentmolekylerna spreds in i polypropenpolymeren under kontakten med membranet, vilket ledde till att membranet svällde. Dessutom undersöktes effekterna av driftsparametrar såsom nedsänkningstid och typ av absorbent i detalj. Slutligen, på grundval av analysresultaten, diskuterades metoder för att underlätta vätningen av membran. Att förbättra polypropylenmembranets hydrofobicitet genom modifiering av ytan föreslogs kunna vara ett effektivt sätt att förbättra den långsiktiga driftprestandan för membranenheter. Därför modifierades de ihåliga fibrerna av polyproylen med ett tunt lager av en superhydrofob beläggning på membranets yta för att förbättra hydrofobiciteten. En blandning av cyklohexanon och metyletylketon ansågs vara det bästa icke-lösningsmedlet för att få en fiber yta med god homogenitet och acceptabelt hög hydrofobicitet. Under lång driftperiod, uppvisade den modifierade membranenheten stabilare och effektivare prestanda än den obehandlade. Därför erbjuder ytbehandling en möjlighet till att förbättra systemets stabilitet för CO2-avskiljning när det gäller långsiktig drift. / VR-SIDA Swedish Research Links Programme

Ces travaux portent sur la conception et le développement d’un procédé membranaire de captage/stockage du CO2 embarqué pour le transport routier. Dans une première partie, nous réalisons la simulation d’un procédé membranaire embarqué de captage du CO2 dans le cas d’un poids lourd (>3500 kg). Ceci comprend l’analyse énergétique de la séparation et de la compression des gaz, l’évaluation des surfaces et volumes requis ainsi que l’autonomie de l’unité de stockage et la surconsommation engendrée par ce dispositif. Nous étudions dans un second temps la relation entre qualité des supports fibres creuses et celle des membranes nanocomposites MFI-alumine synthétisées. Nous nous intéressons ensuite aux performances des membranes nanocomposites dans la séparation CO2/N2 en phase gazeuse. Plus particulièrement nous évaluons l’influence de la substitution isomorphique du silicium par le bore et le germanium, ainsi que l’échange du proton de valence par d’autres atomes, sur la séparation en question. Un chapitre est dédié à l’évaluation des paramètres thermodynamiques (adsorption) et cinétiques (diffusion) de la séparation CO2/N2. Enfin, nous analysons l’influence de la présence de polluants dans le mélange à séparer (eau, NOx, hydrocarbures) sur les performances séparatives des membranes synthétisées. / This work focuses on the conception and development of a membrane-based process for an on-board CO2 capture/storage application. In a first part, we simulate an on-board CO2 capture unit based on a membrane process for the case study of a heavy vehicle (>3500 kg). This study includes an energy analysis of the impact of gas separation and compression on the required membrane surface and module volume, as well the autonomy of the storage unit and the energy overconsumption involved in the process. In a second part, we study the influence of the hollow-fibre support quality on the final intergrowth level of nanocomposite MFI-alumina membranes. Special attention is devoted to the influence of the isomorphic substitution of silica by boron and germanium, and replacement of the counter-cation (proton) by other elements, on the CO2/N2 separation and permeance properties. Next, a complete chapter has been devoted to the evaluation of the thermodynamic (adsorption) and kinetic (diffusion) parameters in the CO2/N2 separation. Finally, we analyze the influence of standard pollutants (water, NOx, hydrocarbons) on the CO2 separation properties of the synthesized membranes.

L'absorption du CO2 à l'ammoniaque au sein d'une colonne garnie est une technologie prometteuse pour capter le CO2 en postcombustion. La fuite d'NH3 engendrée par la volatilité de ce solvant gêne néanmoins le déploiement de ce procédé. Dans cette étude, la faculté des contacteurs membranaires à permettre des performances d'absorption du CO2 intensifiées et des pertes en NH3 réduites par rapport au procédé conventionnel est évaluée. Pour cela, l'emploi de fibres composites innovantes constituées d'une peau dense assurant un transport sélectif du CO2 vis-à-vis de NH3 a été proposé. Compte tenu des propriétés de ces molécules, aucun matériau ne présentait jusqu'alors de sélectivité de séparation favorable au CO2. Des essais de temps-retards ont permis de révéler 6 matériaux fluorés présentant les propriétés de sélectivités inverses recherchées. Le Teflon AF2400, polymère hautement perméable au CO2, a été choisi pour constituer les fibres creuses composites employées lors d'expériences d'absorption. Leurs performances ont été comparées à celles de contacteurs commerciaux microporeux (Oxyphan) et composites (Oxyplus) pour différentes conditions opératoires. Alors qu'aucune expérience stable n'a pu être achevée avec les contacteurs microporeux du fait de la précipitation de sels d'ammonium, les contacteurs composites ont permis des performances de capture supérieures aux objectifs fixés. La modélisation 2D du transfert de matière a permis de révéler le rôle prépondérant du support microporeux dans les performances d'absorption observées. Enfin, une intensification élevée des performances d'absorption du CO2 et des pertes en NH3 fortement réduites par rapport au procédé conventionnel ont pu être démontrées / Aqueous ammonia as a solvent for post-combustion CO2 capture in a packed column is seen as a promising technology. Nevertheless, ammonia volatility is a considerable drawback for its large scale deployment. In this study, the ability of hollow fiber membrane contactors to significantly improve CO2 mass transfer performances while mitigating ammonia losses when compared to packed column is evaluated. In that purpose, the use of innovating composite fibers made of a thin dense layer selective for CO2 over NH3 is proposed. Up to now, a faster permeation of CO2 compared to NH3 in dense polymers was totally unexpected and to our knowledge unexplored. Time-lag experiments have revealed a series of 6 fluorinated structures showing the desired reverse selectivity properties. Teflon AF2400 has been selected as the dense skin of composite fibers used during absorption experiments. Their performances have been compared, for different operating conditions, to those given by commercial microporous (Oxyphan) and composite (Oxyplus) membrane contactors. Due to ammonium salt precipitation issues, no stable experiment has been achieved using microporous membrane contactors. At the opposite, absorption efficiencies higher than post-combustion capture standards have been reached using composite membrane contactors. 2D mass transfer modeling has revealed the controlling role of the microporous support in the observed absorption performances. Finally, high CO2 mass transfer intensification factor and drastically reduced ammonia losses have been shown

Made available in DSpace on 2014-12-17T15:42:20Z (GMT). No. of bitstreams: 1 MoisesRC_TESE.pdf: 5138295 bytes, checksum: 2244f5424aa2282bc24737aca40cf3d2 (MD5) Previous issue date: 2013-04-29 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Topics of research related to energy and environment have significantly grown in recent years, with the need of its own energy as hydrogen. More particularly, numerous researches have been focused on hydrogen as energy vector. The main portion of hydrogen is presently obtained by reforming of methane or light hydrocarbons (steam, oxy, dry or auto reforming). During the methane steam reforming process the formation of CO2 undesirable (the main contributor to the greenhouse effect) is observed. Thus, an oxide material (sorbent) can be used to capture the CO2 generated during the process and simultaneously shifting the equilibrium of water gas shift towards thermodynamically more favorable production of pure hydrogen. The aim of this study is to develop a material with dual function (catalyst/sorbent) in the reaction of steam reforming of methane. CaO is well known as CO2 sorbent due to its high efficiency in reactions of carbonation and easy regeneration through calcination. However the kinetic of carbonation decreases quickly with time and carbonation/calcination cycles. A calcium aluminate (Ca12Al14O33) should be used to avoid sintering and increase the stability of CaO sorbents for several cycles. Nickel, the industrial catalyst choice for steam reforming has been added to the support from different manners. These bi-functional materials (sorbent/catalyst) in different molar ratios CaO.Ca12Al14O33 (48:52, 65:35, 75:25, 90:10) were prepared by different synthesis methodologies, among them, especially the method of microwave assisted self-combustion. Synthesis, structure and catalytic performances of Ni- CaO.Ca12Al14O33 synthesized by the novel method (microwave assisted selfcombustion) proposed in this work has not being reported yet in literature. The results indicate that CO2 capture time depends both on the CaO excess and on operating conditions (eg., temperature and H2O/CH4 ratio). To be efficient for CO2 sorption, temperature of steam reforming needs to be lower than 700 ?C. An optimized percentage corresponding to 75% of CaO and a ratio H2O/CH4 = 1 provides the most promising results since a smaller amount of water avoids competition between water and CO2 to form carbonate and hydroxide. If this competition is most effective (H2O/CH4 = 3) and would have a smaller amount of CaO available for absorption possibly due to the formation of Ca(OH)2. Therefore, the capture time was higher (16h) for the ratio H2O/CH4 = 1 than H2O/CH4 = 3 (7h) using as catalyst one prepared by impregnating the support obtained by microwave assisted self-combustion. Therefore, it was demonstrated that, with these catalysts, the CO2 sorption on CaO modifies the balance of the water gas-shift reaction. Consequently, steam reforming of CH4 is optimized, producing pure H2, complete conversion of methane and negligible concentration of CO2 and CO during the time of capture even at low temperature (650 ?C). This validates the concept of the sorption of CO2 together with methane steam reforming / T?picos de pesquisa relacionados ? energia e meio ambiente t?m crescido significativamente nos ?ltimos anos, com a necessidade de energia pr?pria como o hidrog?nio. Mais particularmente, in?meras pesquisas t?m sido focadas em hidrog?nio como vetor energ?tico. A maior parte de hidrog?nio ? atualmente obtida por reforma do metano ou hidrocarbonetos (vapor, seco, oxi ou auto reforma). Durante o processo de reforma a vapor do metano, a forma??o de CO2 indesej?vel (principal contribuinte ao efeito estufa) ? observada. Dessa forma, um material ?xido (absorbante) pode ser usado para capturar o CO2 gerado durante o processo e ao mesmo tempo deslocar o equil?brio da rea??o de deslocamento g?s-?gua no sentido termodin?mico mais favor?vel ? produ??o de hidrog?nio puro. O objetivo desse estudo consiste em desenvolver um material com dupla fun??o (catalisador/absorbante) na rea??o de reforma a vapor do metano. CaO ? bem conhecido como absorbante do CO2 devido ? sua elevada efici?ncia em rea??es de carbonata??o e f?cil regenera??o por interm?dio da calcina??o. No entanto, a cin?tica de carbonata??o decresce rapidamente em fun??o do tempo e ciclos de carbonata??o e calcina??o. Um aluminato de c?lcio (Ca12Al14O33) deve ser utilizado para evitar a sinteriza??o e aumentar a estabilidade de absorbantes de CaO durante v?rios ciclos. O n?quel, o catalisador industrial escolhido para a reforma a vapor do metano foi adicionado ao suporte em diferentes maneiras. Estes materiais bi-funcionais (absorbante/catalisador) em diferentes raz?es molares CaO.Ca12Al14O33 (48:52, 65:35, 75:25, 90:10) foram preparados por diferentes m?todos de s?ntese, dentre eles, com destaque o m?todo de autocombust?o assistida por microondas (AAM). S?ntese, estrutura e desempenho catal?tico de Ni- CaO.Ca12Al14O33 sintetizado pelo novo m?todo (autocombust?o assistida por microondas) proposto neste trabalho n?o t?m sido reportado na literatura. Os resultados indicam que o tempo de captura de CO2 depende tanto do excesso de CaO quanto das condi??es de funcionamento (como, por exemplo, a temperatura e a raz?o H2O/CH4). Para ser eficiente na absor??o de CO2, a temperatura de reforma a vapor deve ser inferior a 700 ?C. Uma percentagem otimizada correspondente a 75% de CaO e uma raz?o (H2O/CH4 = 1) fornece os resultados mais prometedores uma vez que uma menor quantidade de ?gua evita uma competi??o entre a ?gua e CO2 para a forma??o de carbonato e hidr?xido. Se esta competi??o for mais efetiva (H2O/CH4 = 3) ter-se-ia uma menor quantidade de CaO dispon?vel para absor??o possivelmente devido ? forma??o de Ca(OH)2. Por isso, o tempo de captura foi maior (16h) para a raz?o H2O/CH4 = 1 do que H2O/CH4 = 3 (7h) usando como catalisador reacional aquele preparado por impregna??o do suporte obtido por AAM. Portanto, foi demonstrado que, com esses catalisadores, a absor??o de CO2 por CaO modifica o equil?brio da rea??o de deslocamento g?s?gua. Consequentemente, a reforma a vapor de CH4 ? otimizada, produzindo hidrog?nio puro, concentra??es desprez?veis de CO2 e CO durante o tempo de captura, mesmo a baixa temperatura (650 ? C). Isso confirma o conceito de absor??o in situ de CO2 durante a reforma a vapor do metano