Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / O consumo de gases causadores do efeito estufa tem sido alvo de pesquisa, pois a sua liberaÃÃo em excesso tem sido apontada como uma das principais causas do aquecimento global observado nas Ãltimas dÃcadas. O consumo destes gases surge no ambiente acadÃmico como uma alternativa promissora no caminho do equilÃbrio entre emissÃes e captaÃÃo visando a diminuiÃÃo da sua concentraÃÃo na atmosfera. A reaÃÃo de reforma a seco do metano foi estudada variando-se as condiÃÃes reacionais (temperatura e razÃo CH4/CO2) de modo a obter a condiÃÃo reacional mais indicada (na faixa empregada), para favorecer o consumo dos gases metano e diÃxido de carbono com produÃÃo de gÃs de sÃntese (H2/CO), alÃm de verificar as caracterÃsticas do coque depositado na superfÃcie do catalisador. Os catalisadores sintetizados (Ni/SiO2, Co/SiO2 e NiCo/SiO2) foram caracterizados por absorÃÃo atÃmica, fluorescÃncia de raios-X, isotermas de adsorÃÃo de N2, difraÃÃo de raios-X e reduÃÃo em temperatura programada. Posteriormente aos testes catalÃticos as amostras foram submetidas à anÃlise por oxidaÃÃo em temperatura programada, espectroscopia Raman, microscopia de transmissÃo e microscopia de varredura. Os testes catalÃticos realizados em diferentes temperaturas (550, 675 e 800ÂC) e razÃes CH4/CO2 (0,5, 2,25 e 4,0) mostram relativa superioridade da amostra NiCo/SiO2 no desempenho catalÃtico e sugere que nas condiÃÃes mÃximas (maior temperatura e razÃo CH4/CO2) à possÃvel obter consumo de diÃxido de carbono acima de 90% e produÃÃo de gÃs de sÃntese com razÃo H2/CO prÃximo da unidade. A anÃlise por oxidaÃÃo em temperatura programada, assim como a espectroscopia Raman, microscopia eletrÃnica de transmissÃo e de varredura apontaram para a formaÃÃo de nanotubos de carbono de parede mÃltipla (MWNTs) e carbono amorfo. / The consumption of greenhouse gas has been subject of research since its excessive liberation has been identified as a major cause of global warming observed in recent decades. In the academic the consumption of these gases emerges as a promising alternative to achieve the balance between its emissions and itâs consumption in order to minimize its atmospheric concentration. The reaction of the dry reforming of methane was studied by varying the reaction conditions (temperature and CH4/CO2 ratio) to obtain the most suitable reaction conditions (in the range employed), to promote the consumption of methane and carbon dioxide with production of synthesis gas (H2/CO) and to verify the characteristics of the deposited coke on the catalyst surface. The catalysts synthesized (Ni/SiO2, and Co/SiO2 NiCo/SiO2) were characterized by atomic absorption, fluorescence X-Ray, N2 adsorption isotherms, X-Ray diffraction and temperature programmed reduction. After the catalytic tests the samples were analyzed by temperature programmed oxidation, raman spectroscopy, transmission electron microscopy and scanning electron microscopy. The catalytic tests were conducted at different temperatures (550, 675 and 800ÂC) and reasons CH4/CO2 (0.5, 4.0 and 2.25) demonstrates the superiority of the performance sample NiCo/SiO2 catalyst and suggests that in specifics conditions (higher temperature and ratio CH4/CO2) it is possible to use carbon dioxide above 90% and production of synthesis gas with H2/CO ratio close to unity. Analysis by temperature programmed oxidation, as well as Raman spectroscopy, transmission electron microscopy and scanning electron microscopy indicated the formation of carbon nanotubes multi-wall (MWNTs) and amorphous carbon.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Dry reforming of methane reaction was conducted in the presence of titanate nanotubes (TNTs) modified with Co, Ni and Pt. TNTs were synthesized by hydrothermal treatment and than these solids were either submitted to ion exchange for Ni and Co using hexahydrate nitrate solutions, or they were submitted to wet impregnation with H2Ptl6.6H2O (1% w/w of Pt) solution. The solids were characterized before and after the dry reforming of methane by elemental chemical analysis (CHN), X-ray diffraction (XRD), Raman spectroscopy, nitrogen adsorption-desorption isotherms, thermoprogrammed reduction (TPR), CO2 thermoprogrammed desorption (CO2-TPD), transmission electronic microscopy (TEM), scanning electronic microscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). Raman and XRD results showed the presence of Na2Ti3O7 phase to all sodic nanotubes, while that the nanotubes modified displayed peaks and vibrational modes relative to CoTi3O7, NiTi3O7 and PtOx/Na2Ti3O7 phases. TEM images exhibited tubular morphology composed by multi-walls, as observed by XRD and Raman. SEM-EDS results showed the nanotubes composition with M/Ti ratio lower than the theoretical (value of 0,33), due to the presence of structural water. The XPS results confirmed the presence of M(OH)2 phase (M=Co, Ni or Pt) present on nanotubes surface. TPR patterns suggested the formation of M0/MTiO3 (M = Co, Ni and Pt) after the reduction of the nanotubes at 650 ÂC. The nitrogen adsorption-desorption isotherms of sodic and modified TNTs showed isotherms type IV with an essentially mesoporous structure. CO2-TPD patterns suggested the presence of weak and moderate basic sites in all catalysts, indicating phase transformation due to the decomposition, in situ, of as-prepared nanotubes. The catalyst NiTNT exhibited the highest CO2 and methane conversion at 600 ÂC, with about 43 and 25%, respectively, and H2/CO ratio equal 1, without deactivation over time. PtTNT was lesser susceptible to coking, although sintering remarkably decreased the performance of this solid. On the other hand, PtTNT and CoTNT showed formation of coke over the PtOx/PtTiO3 and Co0/CoTiO3 active phase, respectively, so that the latter solid deactivated during the dry reforming of methane. / A reaÃÃo da reforma seca do metano foi conduzida na presenÃa de nanotubos de titanatos (TNTs) modificados com Co, Ni e Pt. Os TNTs foram sintetizados via tratamento hidrotÃrmico e, posteriormente, foram submetidos à troca iÃnica por Ni e Co, utilizando soluÃÃes de nitrato hexahidratado, ou foram submetidos à impregnaÃÃo via-Ãmida com soluÃÃo de H2PtCl6.6H2O (1% m/m de Pt). Os catalisadores foram caracterizados antes e apÃs reaÃÃo de reforma seca do metano por anÃlise quÃmica (CHN), difraÃÃo de raios-X (DRX), espectroscopia Raman, isotermas de adsorÃÃo-dessorÃÃo de nitrogÃnio, reduÃÃo termoprogramada (TPR), dessorÃÃo termoprogramada de CO2 (TPD-CO2), microscopia eletrÃnica de transmissÃo (TEM), microscopia eletrÃnica de varredura (MEV-EDS) e espectroscopia fotoeletrÃnica de raios-X (XPS). Os resultados de Raman e DRX evidenciaram a presenÃa da fase Na2Ti3O7 para os nanotubos sÃdicos, enquanto que para os nanotubos modificados foram identificados picos e modos vibracionais referentes Ãs fases CoTi3O7, NiTi3O7 e PtOx/Na2Ti3O7. As imagens de TEM exibiram morfologia tubular composta por multiparedes, corroborando com os resultados de DRX e Raman. Os resultados de MEV-EDS mostraram a composiÃÃo dos nanotubos com razÃo M/Ti menor que o teÃrico (0,33), devido à presenÃa de Ãgua estrutural. Os resultados de XPS confirmaram a existÃncia da fase M(OH)2 (M=Co, Ni ou Pt) presentes na superfÃcie dos nanotubos. As curvas de TPR sugeriram a formaÃÃo da fase M0/MTiO3 (M = Co, Ni e Pt), apÃs a reduÃÃo dos nanotubos a 650 ÂC. As isotermas de adsorÃÃo-dessorÃÃo de nitrogÃnio dos TNTs sÃdicos e modificados apresentaram isotermas do tipo IV com estrutura essencialmente formada por mesoporos. Os perfis de TPD-CO2 sugeriram a presenÃa de sÃtios bÃsicos fracos e moderados em todos os catalisadores, indicando mudanÃa de fase devido à decomposiÃÃo in situ dos nanotubos como sintetizados. O catalisador NiTNT apresentou os melhores resultados de conversÃo de CO2 e metano a 600 ÂC, com aproximadamente 43 e 25%, respectivamente, e razÃo H2/CO igual a 0,5, sem desativaÃÃo ao longo do tempo. PtTNT foi menos susceptÃvel à formaÃÃo de coque, embora o fenÃmeno de sinterizaÃÃo tenha desfavorecido o desempenho do sÃlido. Por outro lado, os sÃlidos PtTNT e CoTNT apresentaram formaÃÃo de coque sobre as fases ativas PtOx/PtTiO3 e Co0/CoTiO3, respectivamente, de modo que este Ãltimo sÃlido desativou durante a reaÃÃo da reforma seca do metano.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / Neste trabalho, aluminas mesoporosas dopadas com CeO2, MgO, ZrO2 ou La2O3 demonstraram que a estrutura dos sÃlidos influenciou no comportamento de desativaÃÃo de catalisadores na reforma seca do metano. Os sÃlidos foram caracterizados atravÃs de difraÃÃo de raios-X, anÃlise quÃmica, espectroscopia Raman, reduÃÃo termoprogramada, anÃlises texturais e termogravimÃtrica, microscopia eletrÃnica de transmissÃo e alta resoluÃÃo, antes e apÃs os testes catalÃticos. NÃquel, platina ou rutÃnio foram dispersos sobre os suportes porosos CeO2-Al2O3, ZrO2-Al2O3, MgO-Al2O3 e La2O3-Al2O3, formando distintas fases. Os catalisadores contendo rutÃnio ou platina foram em geral mais ativos na reforma seca do metano quando comparados aqueles contendo nÃquel, devido a maior dispersÃo das espÃcies de PtOx ou Ruo dispersas sobre MgAl2O4 ou CeAlO3. A resistÃncia à degradaÃÃo fÃsica dos sÃlidos contendo platina ou rutÃnio conduziu a um efeito do promotor para a formaÃÃo de espÃcies de carbono lÃbeis. Sobre o catalisador Ru/MgO-Al2O3, as nanopartÃculas de Ruo dispersas em MgAl2O4 foram mais acessÃveis as molÃculas de metano e diÃxido de carbono, apesar de serem as fontes para a formaÃÃo de carbono amorfo, grafite e nanotubos de carbono. / Mesoporous alumina doped with CeO2, MgO, ZrO2 or La2O3 demonstrated that the solid structure influenced on the deactivation behaviour of the catalysts in dry reforming of methane. Solids were characterized by X-ray diffraction, chemical analysis, Raman spectroscopy, termoprogrammed reduction, textural and thermogravimetric analyses and transmission electron microscopy, before and after the catalytic test. Nickel, ruthenium or platinum dispersed on porous CeO2-Al2O3, ZrO2-Al2O3, MgO-Al2O3 and La2O3-Al2O3 resulted in the formation of distinct phases. Catalysts possessing ruthenium or platinum were more active than the nickel counterparts due to the better dispersion of PtOx or Ruo on MgAl2O4 and CeAlO3 phases. The elevated resistance of ruthenium or platinum against physical degradation led to a promoting effect to labile carbon formation. Over Ru/MgO-Al2O3 catalyst, Ruo nanoparticles dispersed on MgAl2O4 were almost certainly accessible to methane and carbon dioxide molecules and the source supporting for the formation of such amorphous reactive carbon, graphite and carbon nanotubes, as well.

Submitted by Rosangela Silva (rosangela.silva3@unioeste.br) on 2018-06-26T15:19:23Z No. of bitstreams: 2 Rodolfo_Andrade_Schaffner.pdf: 5314013 bytes, checksum: 60ba680e6d87297ff08be073dc0f056c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-06-26T15:19:23Z (GMT). No. of bitstreams: 2 Rodolfo_Andrade_Schaffner.pdf: 5314013 bytes, checksum: 60ba680e6d87297ff08be073dc0f056c (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-03-22 / The large production of waste and waste from rural activity must be managed effectively, and cases of treatment by biodigestion are generated more effectively, through the generation of a source of additional income, biogas. Biogas is represented by the mixture rich in CH4 and CO2 and can be used directly by a high temperature or mechanical energy generation, but it is a mixture that can be used as a source of energy of greater value, as synthesis gas. H2 and CO) and in other compounds therefrom, or purified for the choice of hydrogen. In the reform processes it occurs in the presence of catalysts, at high temperatures (600-1200 ºC). For evaluation, many issues that seek more efficient and stable catalysts for these processes, a tertiary operating cities. This work aims to present the results of the study of the conversion of biogas to silica gas using a reforming of the heat measurement system using a high efficiency nickel catalyst supported on Al2O3. Several calcination temperatures of the Al2O3 support (350, 500, 650 and 800 ° C) were studied, as well as the addition of Mg as a promoter (5% by mass). The catalysts were characterized by N2 physiotherapy, X-ray diffraction, desorption at the programmed ammonia temperature and thermogravimetry. The testes were run at 700 ° C, with a spatial distribution of 30 L h-1 gct-1, 1:1 atmosphere and reagent (CH4:CO2). The physical-chemical and activity characteristics of the final Ni/Al2O3 catalysts were studied in the increase of the calcination temperatures generated by the surface areas and pore volume, as well as an increase in the acidity in the lower bands of calcination, and decrease in higher, the greater activity of H2 and CO catalysts. / A grande produção de resíduos e dejetos advindos da atividade rural deve ser gerenciada de forma eficiente sendo que em muitos casos o tratamento por meio de biodigestão anaeróbia é o método mais eficaz, pois gera ao produtor uma possível fonte de renda adicional, o biogás. O biogás é representado pela mistura rica em CH4 e CO2 e pode ser usado diretamente para a geração de energia térmica ou mecânica, porém está mistura pode ser utilizada como insumo para obtenção de outros produtos de maior valor, como gás de síntese (mistura rica em H2 e CO) e em outros compostos a partir deste, ou purificado para obtenção de hidrogênio. Nos processos de reforma a reação ocorre na presença de catalisadores, e em altas temperaturas (600-1200 ºC). Dessa forma, muitos pesquisadores buscam catalisadores mais eficientes e estáveis para estes processos, afim de minimizar as condições operacionais. Este trabalho tem como objetivo apresentar os resultados do estudo da conversão de biogás a gás de síntese, utilizando a reforma a seco (RS) do metano, por meio de reações utilizando catalisadores de níquel de alta eficiência, suportados em Al2O3. Foram estudadas várias temperaturas de calcinação do suporte Al2O3 (350, 500, 650 e 800ºC), além da adição de Mg como promotor (5% em massa). Os catalisadores foram caracterizados por fisissorção de N2, difratometria de raios X, dessorção a temperatura programada de amônia e termogravimetria. Os testes catalíticos foram executados a 700 ºC, com velocidade espacial 30 L h-1 gcat-1, pressão atmosférica e composição da mistura reagente (CH4:CO2) 1:1. Verificou-se que as variáveis estudadas interferem nas características físico-quimicas e de atividade do catalisador final Ni/Al2O3, no qual o aumento das temperaturas de calcinação gerou aumento das áreas superficiais e volume de poros, e também se verificou um aumento da acidez nas faixas mais baixas de calcinação, e redução em temperaturas maiores, o que influenciou na atividade dos catalisadores que mostraram maior atividade em maiores índices de acidez, e em geral melhor formação de H2 e CO.

L’étude concerne un nouveau procédé de reformage du gaz naturel en gaz de synthèse par le dioxyde de carbone (RSM), en vue de l'utilisation rationnelle des déchets carbonés industriels pour la production d'hydrocarbures et d'hydrogène. Cette méthode utilise des systèmes à membranes catalytiques inorganiques (SMC) qui favorisent des réactions catalytiques hétérogènes en phase gazeuse dans des micro-canaux céramiques. La surface active des catalyseurs formés à l'intérieur des canaux est faible en termes de superficie, mais elle est caractérisée par une valeur élevée du facteur Surface/Volume du catalyseur, qui induit une efficacité importante de la catalyse hétérogène. Les SMC, formés à partir de dérivés alcoxy et des précurseurs métalliques complexes, contiennent de 0,008 à 0,055% en masse de nano-composants mono- et bimétalliques actifs répartis uniformément dans les canaux. Pour les systèmes [La-Ce]-MgO-Ti02/Ni-Al et Pd-Mn-Ti02/Ni-Al, les productivités de 10500 et 7500 1/h·dm3membr. ont été respectivement obtenues lors du RSM dès 450°C avec une composition de gaz de synthèse H2/?? allant de 0,63 à 1,25 et un taux de conversion de 50% de la charge CH4/CO2 (1/1). Ainsi les SMC sont d’un ordre de grandeur plus efficace qu’un réacteur à lit fixe du même catalyseur. Le RSM est initié par l'oxydation de CH4 par l'oxygène de structure des oxydes métalliques présents en surface, et le CO2 réagit avec le carbone finement divisé provenant de la dissociation de CH4. Une synergie catalytique a été mise en évidence pour le système Pd-Mn. Ces SMC de 108 pores par cm² de surface constituent un ensemble de nano réacteurs de fort potentiel industriel (synthèse d’oléfines, biomasse) / This study reports the development of a new process to convert methane and carbon dioxide (dry methane reforming - DMR) into valuable products such as syngas from non-oil resources. The practical interest is to produce syngas from carbon containing exhaust industrial gases. This process uses membrane catalytic systems (MCS) that support heterogeneous catalytic reactions in gaseous phase in ceramic micro-channels. The active surface of the catalysts formed inside the micro-channels is low in term of area, but it is characterized by a high value of the catalyst surface/volume ratio, which induces a high efficiency of heterogeneous catalysis. The SMC are formed from alkoxy derivatives and precursor metal complex containing between 0.008 and 0.055% by weight of nano-components mono-and bimetallic active distributed evenly in the channels. For systems [La-Ce] -MgO-Ti02/Ni-Al and Pd-Mn-Ti02/Ni-Al, productivities of 10500 and 7500 l/h · dm3 membr. were respectively obtained by RSM at 450°C with a composition of syngas H2/?? ranging from 0.63 to 1.25 and a conversion rate of 50% with a CH4/CO2 (1/1) feed. Thus the CMS is an order of magnitude more efficient than a fixed bed reactor of the same catalyst. The MDR is initiated by the oxidation of CH4 by structural oxygen of metal oxides available on the surface, and the CO2 reacts with the finely divided carbon arising from the dissociation of CH4. A catalytic synergy has been demonstrated for the system Pd-Mn. This CMS, having 108 pores per cm² of surface, can be considered as a set of nano reactors. Thus this new approach is very promising for industry (synthesis of olefins, uses of biomass)

Research was curried out on the perovskite systems with general formula A1-xA‘xB1-yB‘yO3± (where A=La, Sm, A´=Ca, B´=Al, B=Co,Fe,Mn and Cr). Perovskite oxides were sythesized by polymerisation methods and characterised by RTG analysis, BET method, SEM and EDX. TPD spectra and catalyst testing were measured in high temperature plug flow reactor and products were analysed by mass spectrometry. It was found, that metane oxidation at ratio O2/CH40,5 depended on the temperature. Total oxidation proceeded at the temperature betwen 300-700oC to the carbon dioxide and water, while the partial oxidation of metane (POM) occured at above 700oC to the hydrogen and carbon oxid (syngas). This was ascribed by equilibrium of O2 betwen gas phase and solid perovskite. There was used 12 perovskite systems, which catalysed methane oxidation by the same way. Dry reforming of methane run above temperature 700oC. Cobaltite and ferite type perovskites were found as the most active catalytic systems. On the base of obtained results the Mars van Krevelen mechanism was established for explanation of oxidation and reformation of methane by perovskite systems. It was showed, that POM was running by two steps mechanism. Products of total oxidation was occured in the first step, which were passed over to the syngas (H2+CO) in the second step.

Dry reforming of methane is an important reaction to generate syngas from two greenhouse gases. The syngas can be used in Fishcher-Tropsch synthesis to produce valueded chemicals. Chapter I reviews the catalytic conversion of methane and carbon dioxide to syngas, including DRM reaction chemistry, catalysts used in this process, catalyst deactivation, and the kinetics of DRM reaction. Chapter II discusses the development of bimodal pore NiCeMgAl catalysts for DRM reaction. Bimodal pore NiCeMgAl catalysts were synthesized via the refluxed co-precipitation method and systematically investigated the influence of active metal loading, calcination temperature, reduction temperature and gas hourly space velocity (GHSV) on the catalytic performance of DRM reaction. The Ni15CeMgAl sample with 15 wt% NiO loading was found to be active enough at 750 °C with a high CH4 conversion of 96.5%. The proper reduction temperature for the NiCeMgAl catalyst is either 550–650 °C or 850 °C. Higher calcination temperature favors the formation of NiAl2O4 and MgAl2O4 spinel structures. Compared with non-bimodal pore NiCeMgAl catalyst, bimodal pore NiCeMgAl catalyst has a longer stability in the feed gas without dilution. In chapter III, the kinetic behavior of bimodal pore NiCeMgAl catalyst for DRM reaction was investigated after the elimination of external and internal diffusion effects in a fixed-bed reactor as a function of temperature and partial pressures of reactants and products. A Langmuir-Hinshelwood model was developed assuming that the carbon deposition is ignorable but the RWGS reaction is non-ignorable and the removal of adsorbed carbon intermediate is the rate-determining step. A nonlinear least-square method was applied to solve the kinetic parameters. The derived kinetic expression fits the experimental data very well with a R2 above 0.97, and predicts the products flow rate satisfactorily. Chapter IV documents the results of in situ XRD study on the NiMgAl catalyst for DRM reaction. The phase evolution of a NiMgAl oxide catalyst at the reduction stage was qualitatively analysed and quantitatively determined by employing the continuous changes in XRD intensity and TPR information. The stable crystallite size of both active metal and spinel support is responsible for the long stability of NiMgAl catalyst without carbon deposition during the DRM reaction.

No description available.

Supported Ni and Rh catalysts were developed for the reforming of two greenhouse gases, methane and carbon dioxide to syngas (a mixture of hydrogen and carbon monoxide). This is an endothermic, equilibrium limited reaction. To overcome the thermodynamic limitations, a commercially available porous membrane (Vycor glass) was used in a combined reactor-separator configuration. This was to selectively remove one or more of the products from the reaction chamber, and consequently shift the equilibrium to the right. However, the separation mechanism in this membrane involved Knudsen diffusion, which provided only partial separations. Consequently, there was some transport of reactants across the membrane and this led to only marginal improvements in performance. To overcome this limitation, a new membrane was developed by modifying the Vycor substrate by the chemical vapor deposition of a silica precursor. This new membrane, termed Nanosil, provided high selectivity to hydrogen at permeabilities comparable to the support material. Application of this membrane in the combined reactor-separator unit provided higher conversions than that obtained using the Vycor membrane. / Ph. D.

Ce travail a porté sur la conversion du méthane en hydrogène par les procédés de vaporeformage et reformage à sec, utilisant de nouvelles formulations de catalyseurs afins d'augmenter la sélectivité en produit désiré (H₂), de réduire la production du monoxyde de carbone (CO) et défavoriser la formation de coke. Deux familles de catalyseurs, à base de nickel et de ruthénium supportés par la cérine et/ou l'alumine, ont été évaluées dans ces réactions. Il a été montré que les catalyseurs à base de ruthénium supportés par l'alumine présente une bonne activité catalytique et une très bonne résistance au dépôt de coke dans les réactions de reformage du méthane. La cérine joue un rôle déterminant dans les catalyseurs à base de nickel en favorisant la dispersion de la phase active et évitant la formation des agglomérats. Parallèlement, une inhibition de la formation de coke est observée grâce aux propriétés redox du solide. Les travaux ont porté également sur l'amélioration de la formulation des catalyseurs monométalliques, et un catalyseur bimétallique (Ru-Ni/CeO₂-Al₂O₃) actif, sélectif et stable pour la production d'hydrogène à partir du méthane a été mis au point. L'ajout d'un deuxième métal en faible teneur (0,5%) aide à maintenir le Ni sous sa forme actif empêchant la formation de coke sur la surface du catalyseur. Pour les deux réactions étudiées, les excellentes performances obtenues proviennent essentiellement de l'ajustement des paramètres de réaction et les paramètres de préparation des catalyseurs, ce qui ouvre de réelles perspectives d'application industrielle. / This work has focused on the methane conversion by steam reforming and dry reforming processes, through new catalyst formulations in order to increase the selectivity of expected products (H₂), to reduce carbon monoxide production (CO) and to limit the coke formation. Two categories of catalysts were evaluated in these reactions : nickel-based catalysts and ruthenium-based catalysts supported by ceria and/or alumina. It has been reported that the ruthenium-based catalysts supported by alumina provide important catalytic activity and high resistance to coke deposition in the methane reforming reactions. Ceria played a determining role in the nickel-based catalysts by enhancing the active phase dispersion without agglomerates and coke formation. Works have also continued on the improvement of the monometallic catalyst and an active bimetallic catalyst (Ru-Ni/CeO₂-Al₂O₃), selective and stable in hydrogen production from methane has been developed. The addition of a second metal helps maintaining Ni in its active form, preventing the coke formation on the catalyst surface. For the two considered reactions, the excellent performance was largely due to the adjustment of the reactions and catalyst parameters offering a real potential industrial application.