Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-08-30T14:36:54Z No. of bitstreams: 1 DISSERT_ANDRE_MARTINS.pdf: 4991704 bytes, checksum: cc6c14ad89dc58184e8a48c959434b27 (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-08-31T17:43:22Z (GMT) No. of bitstreams: 1 DISSERT_ANDRE_MARTINS.pdf: 4991704 bytes, checksum: cc6c14ad89dc58184e8a48c959434b27 (MD5) / Made available in DSpace on 2016-08-31T17:43:22Z (GMT). No. of bitstreams: 1 DISSERT_ANDRE_MARTINS.pdf: 4991704 bytes, checksum: cc6c14ad89dc58184e8a48c959434b27 (MD5) / CNPQ / A reforma a vapor de metano é a principal via de produção de hidrogênio e de gás de síntese. Industrialmente, esta reação ocorre sobre um catalisador de níquel suportado em alumina que, embora apresente alta atividade e seletividade, além de baixo custo, tem a desvantagem de apresentar uma curta vida útil, devido à deposição de coque. Por outro lado, os metais nobres apresentam mais alta atividade catalítica e mais resistência à deposição de coque e à sinterização do que o catalisador comercial. Além disso, a adição de magnésio à alumina é uma boa opção para evitar a deposição de coque e, também, aumentar a resistência térmica do sólido. Considerando essas vantagens estudou-se, neste trabalho, o efeito da adição de magnésio sobre as propriedades de um catalisador de platina suportada em alumina, a fim de desenvolver novos e eficientes catalisadores para produzir hidrogênio, a partir da reforma a vapor do metano. As amostras com razões molares Al/Mg=0,2, 2 e 5 foram preparadas pelo método de precipitação e impregnadas com 1 % (m/m) de platina. Os sólidos foram caracterizados por análise química, termogravimetria, análise térmica diferencial, espectroscopia de infravermelho com transformadas de Fourier, difração de raios X, redução à temperatura programada, medida da área superficial específica e de porosidade, espectroscopia de infravermelho com transformadas de Fourier usando monóxido de carbono como molécula sonda, dessorção à temperatura programada de amônia adsorvida, espectroscopia fotoeletrônica de raios X e medida do teor de carbono. Os catalisadores foram avaliados a 600 oC e 1 atm, sob uma razão vapor/metano = 4. Os catalisadores mais ricos em alumínio (sem magnésio e com Al/Mg= 5) mostraram a estrutura da γ-alumina, enquanto os demais mostraram a estrutura da periclase. A presença de magnésio diminuiu a área superficial específica da alumina devido à mudança de estrutura. A interação entre a platina e o suporte também aumentou com a quantidade de magnésio, que também alterou a natureza e a quantidade dos sítios ácidos nos sólidos. De modo geral, o magnésio aumentou a quantidade de platina na superfície dos catalisadores e a quantidade de átomos de platina ricos em elétrons, como conseqüência do aumento de sua interação com o suporte. Todos os catalisadores foram ativos na reforma a vapor do metano e seletivos ao hidrogênio. Numa tendência geral, o magnésio favoreceu a atividade e seletividade dos catalisadores. A amostra com Mg/Al= 5 foi o catalisador mais ativo e seletivo, o que pode ser relacionado à sua área superficial específica mais alta, assim como ao teor mais elevado de átomos de platina mais ricos em elétrons na superfície. / Methane steam reforming is the main route to produce hydrogen and synthesis gas. Industrially, this reaction occurs on an alumina-supported nickel catalyst which, although shows high activity and selectivity, besides low price, it has the disadvantage of showing short life because of coke deposition. On the other hand, noble metals show high activity and are more resistant against coke deposition and sintering than the commercial catalyst. Besides, the addition of magnesium to alumina seems to be a good option to prevent coke deposition and also to increase the thermal resistance. Considering these advantages, the effect of magnesium addition on the properties of alumina-supported platinum was studied in this work, aiming to develop new efficient catalysts to produce hydrogen by methane steam reforming. Samples with Al/Mg (molar) = 0.2, 2 and 5 were prepared by precipitation method and impregnated with 1% (w/w) platinum. The solids were characterized by chemical analysis, thermogravimetry, differential thermal analysis, Fourier transform infrared spectroscopy, X-ray diffraction, temperature programmed reduction, specific surface area and porosity measurement, Fourier transform infrared spectroscopy using carbon monoxide as probe molecule, temperature programmed desorption of ammonia, X-ray photoelectron spectroscopy and carbon content measurement. The catalysts were evaluated at 600 oC and 1 atm, under a steam to methane molar ratio of 4. The catalysts richer in alumina (magnesium-free and with Al/Mg= 5 and 2) showed the γ-alumina structure while the others showed the periclase structure. The presence of magnesium increased the specific surface area of alumina because of the change in the structure. The interaction between platinum and the support also increased with the amount of magnesium which also changed the kind and the amount of acidic sites. As a whole magnesium also increased the amount of platinum on the catalyst surface and of electron-rich platinum atoms, as a consequence of the increase of its interaction with the support. All catalysts were active in methane steam reforming and selective to hydrogen. In a general tendency, magnesium favored the activity and selective of the catalysts. The sample with Al/Mg= 5 was the most active and selective catalyst, a fact that was related to its highest specific surface area as well as to the highest amount of electron-richest platinum atoms on the surface.

Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2016-09-26T13:21:16Z No. of bitstreams: 1 Versão final_Juliane Lima.pdf: 3005841 bytes, checksum: ce8a2d085212284f1f3504f349cae58c (MD5) / Approved for entry into archive by Vanessa Reis (vanessa.jamile@ufba.br) on 2016-09-26T14:18:35Z (GMT) No. of bitstreams: 1 Versão final_Juliane Lima.pdf: 3005841 bytes, checksum: ce8a2d085212284f1f3504f349cae58c (MD5) / Made available in DSpace on 2016-09-26T14:18:35Z (GMT). No. of bitstreams: 1 Versão final_Juliane Lima.pdf: 3005841 bytes, checksum: ce8a2d085212284f1f3504f349cae58c (MD5) / CNPq / O biodiesel é um combustível limpo derivado de fontes renováveis, óleos vegetais ou gordura animal. Na sua produção, cerca de 10% em massa do óleo vegetal utilizado como insumo é convertido em glicerina, existindo, dessa forma, grande incentivo para a utilização deste subproduto. Por outro lado, a reforma a vapor da glicerina é um processo com grande potencial para a produção de hidrogênio destinado às células a combustível e aos motores de combustão interna. De modo a obter catalisadores alternativos para a reforma a vapor de glicerina, neste trabalho, foram preparados sólidos baseados em níquel e/ou rutênio suportado(s) em óxido de lantânio a partir de dois métodos: (i) impregnação de nitrato de níquel e/ou de rutênio em óxido de lantânio para obter amostras do tipo (NiO)1-x(RuO)x/La2O3 e (ii) decomposição de sólidos com estruturas perovskita do tipo LaNi1-xRuxO3 (x= 0, 0,1 e 1). Os catalisadores foram obtidos por redução desses precursores a 650, 800 ou 1000 oC, dependendo do método de preparação ou amostra, sob fluxo de hidrogênio. As amostras foram caracterizadas por espectroscopia no infravermelho com transformada de Fourier, difração de raios X, medida de área superficial específica e redução à temperatura programada. A avaliação dos catalisadores na reação de reforma a vapor do glicerol (como molécula modelo) foi conduzida sob pressão atmosférica a 600 ºC, por 5 h. Após a reação, determinou-se o teor de coque depositado sobre os catalisadores. Os sólidos obtidos por impregnação, constituídos por óxido de lantânio, óxido de rutênio, óxido de níquel (NiO) e/ou de compostos de níquel e lantânio (LaNiO3 e La2NiO4), apresentaram áreas superficiais específicas baixas (1,5-11 m².g-1). No caso das amostras obtidas por aquecimento de perovskitas, houve a formação de sólidos com estruturas cristalinas com simetria romboédrica ou ortorrômbica, com áreas superficiais específicas ainda mais baixas (0,5-4,7 m².g-1). Esses sólidos foram mais redutíveis que aqueles obtidos por impregnação e, em todos os casos, o rutênio aumentou a redutibilidade dos sólidos. A atividade e seletividade dos catalisadores obtidos variaram com o método de preparação e a composição dos catalisadores. Quando introduzido no catalisador por impregnação, o rutênio diminuiu a atividade do catalisador de níquel, que foi aumentada no sólido oriundo de perovskitas. As conversões variaram de 68 a 97 % e, em todos os casos, o níquel foi mais ativo que o rutênio. O rendimento a hidrogênio também variou com a presença do rutênio e com o método de preparação dos sólidos. Quando preparados por impregnação, os catalisadores monometálicos conduziram a valores mais elevados que os bimetálicos. Quando obtidos por decomposição de perovskitas, o catalisador isento de níquel levou aos mais baixos valores de rendimento, enquanto aquele contendo os dois metais levou ao valor mais elevado. A presença de rutênio diminui a quantidade de coque formado sobre os catalisadores, durante a reforma a vapor da glicerina, apenas quando os sólidos foram obtidos por impregnação. A amostra contendo níquel e rutênio, e obtida por decomposição de perovskitas, foi o catalisador mais promissor, conduzindo a uma conversão de 97%, rendimento a hidrogênio de 76%. / Biodiesel is a clean renewable fuel derived from vegetable oils or animal fat. About 10% by weight of vegetable oil used as a feedstock is converted into glycerin in its production and thus its use is largely encouraged. On the other hand, the steam reforming of glycerin is a great potential process for the production of hydrogen to feed fuel cells and internal combustion engines. In order to obtain alternative catalysts for steam reforming of glycerin nickel and/or ruthenium supported on lanthanum oxide were prepared in this work by two methods: (i) by impregnation of nickel nitrate and/or ruthenium on lanthanum oxide to obtain (NiO)1-x(RuO)x/La2O3 samples and (ii) by decomposition of solids with perovskite-type structures such as LaNi1-xRuxO3 (x = 0, 0.1 and 1). The catalysts were obtained by reduction of these precursors at 650, 800 or 1000 oC, depending on the method of preparation or sample under hydrogen flow. The samples were characterized by Fourier transform infrared spectroscopy, X- ray diffraction, specific surface area measurements and temperature programmed reduction. The catalysts were evaluated in steam reforming of glycerol (as a molecule model) under atmospheric pressure at 600 oC, for 5 h. After reaction, the coke deposited on the catalyst was determined. The solids obtained by impregnation consisted of lanthanum oxide, ruthenium oxide, nickel (NiO) and/or nickel and lanthanum compounds (LaNiO3 and La2NiO4) oxide, showed low specific surface areas (1.5-11 m². g-1). In the case of the samples prepared by heating perovskites, solid crystalline structures with rhombohedral or orthorhombic symmetry were obtained with specific surface areas even lower (0.5-4.7 m².g-1). These solids were more reducible than those obtained by impregnation and ruthenium increased the reducibility of the solids for all cases,. The activity and selectivity of the catalysts changed with the preparation method and with the catalysts composition. When introduced into the catalyst by impregnation, ruthenium decreased the activity of the nickel-based catalyst, whose activity increased in the solid originating from perovskites. The conversions ranged from 68 to 97% and nickel was more active than ruthenium for all cases. The hydrogen yield also varied depending on ruthenium and on the preparation method of the solid. When prepared by impregnation, the monometallic catalysts led to higher values than the bimetallic ones When obtained by decomposition of perovskite, the free-nickel catalyst led to lower yields while those containing the two metals led to the highest value. The presence of ruthenium reduces the amount of coke formed on the catalyst during the steam reforming of glycerin, only when the solids were prepared by impregnation. The sample containing nickel and ruthenium and obtained by decomposition of perovskites was the most promising catalyst, leading to a conversion of 97%, hydrogen yield 76%.

Made available in DSpace on 2016-06-02T19:56:56Z (GMT). No. of bitstreams: 1 6201.pdf: 1691871 bytes, checksum: 6c83b1bac5cb0a7669949d88fb279a1b (MD5) Previous issue date: 2014-02-21 / Financiadora de Estudos e Projetos / Acetic acid (AA), one majority substance contained in the bio-oil from biomass pyrolysis, was used as a model molecule for study of reaction routes of steam reforming on Ni/&#952;-Al2O3 catalysts. The catalyst containing 15% nickel (w/w), prepared by wet impregnation in a &#952;-Al2O3. The samples were characterized: nitrogen adsorption, ammonia desorption, X-ray diffraction, temperature programmed reduction and thermogravimetric analysis. The reaction routes were studied using: a) temperature programmed desorption (TPD), b) temperature programmed decomposition e c) temperature programmed steam reforming (TPSR) with ratios of 3:1, 6:1 or 9:1 of H2O: AA. The results of TPD where AA was adsorbed and decomposed in function of temperature, show simultaneous desorption of CO, CO2, H2 and CH4 which is explained by the formation of acetic anhydride on the surface of Ni which decomposes into CH3COO* and/or CH3CO* and then CO, CO2 and H2. The TPSR results suggest that the reaction route of decomposition and reform of AA depend on the temperature and the ratio H2O:AA. At low temperatures (< 650 K) and low ratios H2O:AA has the formation of CO and CO2 via bond breaking C-C of species CH3COO* and CH3CO* formed from acetic anhydride. With increasing temperature the anhydride formation is disfavored, in region between 600-800 K, there is interaction and dimerization of AA molecule adsorbed on Ni, which leads to the formation of C2H4. At the same time to this reaction, the formation of CH4 is verified by the hydrogenation CH3* species formed by breaking of CH3COO* and/or CH3CO* species. In high temperatures (> 800 K) methane formation is favored, possibly by decomposition of species CH3 in C* e H2, C* is oxidized by water. In highest ratio (9:1), the formation of the anhydride is not favored and the reforming reactions occur via decomposition of CH3COO* species. In low temperature, formation of CH4 is not observed and the oxidation of CH3* species may occur via the formation of formates. With increasing temperature oxidation of these CH3* radicals via pyrolytic should be favored. / O ácido acético (AA), uma das principais substâncias contidas no bio-óleo proveniente de pirólise de biomassa, foi utilizado como molécula modelo no estudo das rotas de reação da reforma a vapor sobre catalisadores de Ni/&#952;-Al2O3. O catalisador, contendo 15 % em massa de níquel, foi preparado por impregnação úmida utilizando-se uma &#952;-Al2O3. As amostras foram caracterizadas por fisissorção de nitrogênio, dessorção de amônia, difração de raios-x, redução a temperatura programa e análise termogravimétrica. As rotas reacionais foram estudadas utilizando-se: a) dessorção a temperatura programa de AA (TPD), b) decomposição do AA e c) reações de reforma a vapor do AA (TPSR), com razões molares de H2O: AA de 3:1, 6:1 ou 9:1. Os resultados de TPD, onde o AA foi adsorvido e decomposto em função da temperatura, mostra a dessorção simultânea de CO, CO2, H2 e CH4 que é explicada através da formação de anidrido acético sobre a superfície do Ni o qual se decompõe em CH3COO* e/ou CH3CO* e em seguida CO, CO2 e H2. Os resultados de TPSR sugerem que as rota reacionais para decomposição e reforma do AA dependem da temperatura e da razão H2O:AA. Em baixa temperatura (< 650 K) e baixas razões H2O: AA tem-se a formação de CO e CO2 via quebra da ligação C-C das espécies CH3COO* e CH3CO* formadas a partir do anidrido acético. Com o aumento da temperatura a formação de anidrido é desfavorecida e em temperaturas na região entre 600-800 K, tem-se a interação e dimerização da molécula AA adsorvido sobre o Ni, que leva a formação de C2H4. Em paralelo a esta reação verifica-se a formação de CH4 através da hidrogenação das espécies CH3* formados por quebra das espécies CH3COO* e/ou CH3CO*. Em altas temperaturas (> 800 K) a formação de metano é desfavorecida, possivelmente pela decomposição dos espécies CH3 em C* e H2, sendo C* oxidado pela água. Já em alta razão (9:1), a formação do anidrido não é favorecida e a reação de reforma ocorre via decomposição de espécies CH3COO*. Em baixa temperatura a formação de CH4 não é observada e a oxidação das espécies CH3* podem ocorrer via a formação de formiatos. Com o aumento de temperatura a oxidação desses radicais CH3* via pirolítica deve ser favorecida.

Made available in DSpace on 2016-06-02T19:56:37Z (GMT). No. of bitstreams: 1 2931.pdf: 6814472 bytes, checksum: 46c69cfcaa07e8f2ab4e1d803b03916a (MD5) Previous issue date: 2010-03-05 / Universidade Federal de Minas Gerais / Colloidal Nanoparticles of Platinum (Pt-NPs) were obtained by reducing hexacloroplatinic acid with ethylene glycol in the presence of polyvinylpyrrolidone (PVP) as protective agent of the particles. Two methods of synthesis were performed which differed by the ratio PVP / Pt used. The synthesis of nanoparticles was accompanied by measures in the UV-visible from of which it was possible to determine the end of the reaction. The Pt-NPs were characterized by Transmission Electron Microscopy (TEM) that determined the average diameter of particles (~ 2.0 nm). After the synthesis, the Pt-NPs were incorporated into the supports of alumina and alumina promoted with cerium and cerium-zirconium which were prepared by sol-gel method. Supporters with nanoparticles incorporated were then subjected to heat treatment have sought the formation of stable catalysts and without the presence of protective polymer, as this could affect the activity of the catalyst by covering the active sites. Through X-ray diffraction and TEM images it was possible to monitor the stability of samples after heat treatment and the samples that were synthesized with higher PVP were more stable. Measures of X-ray absorption fine structure (XAFS) spectroscopy in situ allowed the characterization of the samples in the reaction atmosphere. Through the analysis of extended X-ray absorption fine structure (EXAFS) was observed morphological changes in the particles caused by the increase in temperature showing that there is an increase in the number of atoms of low coordination when samples are heated which favors the reaction of steam reforming of methane. Through studies of X-ray absorption near edge structure (XANES) in the edges L2 and L3 of Pt was possible to monitor how the electron density of the catalysts varies in reaction conditions. Moreover, the catalysts were also tested catalysts. Measures of dispersion were obtained by the reaction of dehydrogenation of cyclohexane and catalysts made of alumina promoted with cerium and cerium-zirconium displayed less dispersion due to the coating caused by the support. The catalysts in which the particles were synthesized with a higher amount of PVP, because of its stability, were subjected to the reaction of steam reforming of methane and proved active. This reaction was used to calculate the value of the apparent activation energy. The catalysts containing promoters were more active than the catalyst only alumina thus showing the role of support in this reaction. Therefore, this system has proved very interesting to study the catalytic properties in reactions sensitive to the structure since the nanoparticles present are monodispersed and the catalyst is stable under reaction conditions allowing the study of structural and electronic properties. / Nanopartículas coloidais de platina (NPs-Pt) foram obtidas por meio da redução do ácido hexacloroplatínico por etilenoglicol na presença de polivinilpirrolidona (PVP) como agente protetor das partículas. Dois métodos de síntese foram realizados os quais se diferiram pela razão PVP/Pt empregada. As sínteses das NPs-Pt foram acompanhadas por medidas no UVvisível através das quais foi possível determinar o fim da reação. As NPs-Pt foram caracterizadas por microscopia eletrônica de transmissão (TEM) que determinou o diâmetro médio das partículas (~2,0 nm). Após a síntese as NPs-Pt foram incorporadas à suportes de alumina e alumina promovida com cério e cério-zircônio os quais foram preparados pelo método sol-gel. Os suportes com as nanopartículas incorporadas foram então submetidos a tratamentos térmicos com o objetivo de levar à formação de catalisadores estáveis e sem a presença do polímero protetor. Através de difração de raios X e imagens de TEM foi possível acompanhar a estabilidade das amostras após o tratamento térmico tendo sido as amostras sintetizadas com maior quantidade de PVP mais estáveis. Medidas de espectroscopia de estrutura fina de absorção de raios X (XAFS) in situ permitiram a caracterização da amostra em atmosfera de reação. Através da análise da região estendida após a borda, EXAFS, foi possível observar mudanças morfológicas nas partículas ocasionadas pelo aumento da temperatura mostrando que há um aumento no número de átomos de baixa coordenação quando as amostras são aquecidas o que favorece a reação de reforma a vapor do metano. Através de estudos da região próxima às bordas L2 e L3 da Pt (XANES) foi possível acompanhar como a densidade eletrônica dos catalisadores variou em condições de reação. Por fim, os catalisadores foram submetidos a ensaios catalíticos. Medidas de dispersão foram obtidas através da reação de desidrogenação do ciclohexano tendo os catalisadores preparados com alumina promovida com Ce e Ce-Zr apresentado uma menor dispersão devido ao recobrimento ocasionado pelo suporte. Devido à sua estabilidade, os catalisadores obtidos a partir das nanopartículas sintetizadas com maior razão PVP/Pt, foram submetidos à reação de reforma a vapor do metano e se mostraram ativos. Essa reação foi utilizada para calcular o valor da energia de ativação aparente. Os catalisadores contendo promotores foram mais ativos, mostrando assim o papel do suporte nessa reação. Portanto, essa abordagem se mostrou bastante interessante para o estudo das propriedades catalíticas em reações sensíveis à estrutura devido à estreita distribuição de tamanhos das nanopartículas e sua estabilidade em condições de reação permitindo o estudo detalhado de suas propriedades estruturais e eletrônicas

Submitted by Luanna Matias (lua_matias@yahoo.com.br) on 2015-03-05T14:07:37Z No. of bitstreams: 2 Dissertação - Alécia Maria Golçalves - 2011.pdf: 3110848 bytes, checksum: 0b6c29c9a2a058e2fd9e9c31230c02a6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luanna Matias (lua_matias@yahoo.com.br) on 2015-03-05T16:24:15Z (GMT) No. of bitstreams: 2 Dissertação - Alécia Maria Golçalves - 2011.pdf: 3110848 bytes, checksum: 0b6c29c9a2a058e2fd9e9c31230c02a6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-03-05T16:24:15Z (GMT). No. of bitstreams: 2 Dissertação - Alécia Maria Golçalves - 2011.pdf: 3110848 bytes, checksum: 0b6c29c9a2a058e2fd9e9c31230c02a6 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2011-09-12 / The reaction of steam reforming of ethanol is a way produce hydrogen gas, but it is essential to use catalysts to facilitate this reaction. This paper proposes the preparation of nanostructured catalysts impregnated with titanium oxide nanoparticles of cobalt and/or magnesium oxide. From the results of XRD, TEM and BET titanium oxide (anatase - T) obtained from the sol-gel method showed particles with crystallite size of 5-8 nm and a specific surface area of 258 m2g-1. The sodium titanate nanotubes were synthesized by alkaline hydrothermal treatment of titanium oxide in anatase phase, commercial (NT) and synthesized (NTS), resulting in nanotubes with outer diameter from 10 to 30 nm and length of 45 to 110 nm. The impregnation process of the oxides of cobalt and/or magnesium did not cause structural changes in the supports, and present level of metal below the desired level. Profiles of temperature programmed reduction showed the presence of cobalt oxide in the impregnated catalysts. The catalysts evaluated in the reaction of reforming ethanol (Co3O4, NT, NTCo, NTMgCo, and NTMgCo700 NTSMgCo) had ethanol conversion close to 100%, and the catalysts NTSMgCo, NTMgCo700 showed higher selectivity to 87.8% and 89,2%, respectively. With the exception of NT and NTCo catalysts showed no formation of ethylene. The amount of carbon after the catalytic tests ranged from 3.4 to 12.9 (%m/m/h). / A reação de reforma a vapor do etanol é uma forma de produzir o gás hidrogênio, porém é imprescindível a utilização de catalisadores para viabilizar esta reação. Este trabalho propõe catalisadores nanoestruturados de titânio impregnado com nanopartículas de óxido de cobalto e/ou óxido de magnésio. A partir dos resultados de DRX e MET e BET o TiO2 - anatásio obtido a partir do método sol-gel apresentou nanopartículas com tamanho de cristalitos de 5 - 8nm e uma área superficial específica de 258m2g-1. Os nanotubos de titanatos de sódio foram sintetizados por tratamento hidrotérmico alcalino de óxidos de titânio - anatásio com tamanhos de partículas diferentes, apresentaram diâmetro externo de 10 - 30nm e comprimento de 45 - 110 nm. As curvas termogravimétricas mostraram que a decomposição térmica está relacionada à eliminação de água. O processo de impregnação dos diferentes óxidos de cobalto e/ou magnésio apresentou teores menores que o desejado e não proveram alterações estruturais nos nanotubos. O RTP do Co3O4 apresentou três bandas de redução, com máximos em 445, 550 e 660 °C e estas bandas também foram identificadas nos catalisadores impregnados com Co3O4. Os catalisadores Co, NT, NTCo, NTMgCo, NTMgCo700 e NTSMgCo apresentaram conversão do etanol próximo a 100%, sendo que os catalisadores NTSMgCo, NTMgCo700 apresentaram maior seletividade a H2 87,8% e 89,2%, respectivamente, e NTMgCo apresentou seletividade a H2 81,4 % e não formou acetaldeído. Após os testes catalíticos foram observados a deposição de carbono, variando 10 – 53%.

Neste trabalho foram preparados catalisadores Co/Al2O3 e Co/SiO2 por impregnação com concentração metálica entre 4,0% e 20,0% e avaliados frente às reações de reforma a vapor e reforma oxidativa de etanol, com o objetivo de avaliar a estabilidade catalítica e o rendimento em hidrogênio. Os catalisadores foram caracterizados por espectrofotometria de absorção atômica, difração de raios-X, espectroscopia Raman, redução a temperatura programada, fisissorção de nitrogênio e análise elementar de carbono. A caracterização das amostras mostrou a formação da fase Co3O4 e interações de espécies de cobalto com o suporte. Evidenciou-se que apenas os sítios de Co0 são ativos para as reações de reforma a vapor e oxidativa de etanol. A produção de hidrogênio variou de 50-70% e a de CO de 0-10%. Alta concentração metálica sobre a superfície do suporte acarretou uma baixa produção de monóxido de carbono. As reações tiveram deposições de carbono nos catalisadores variando de 2,7 a 12,7 (mg. h-1), indicando que a desativação dos materiais é devido a deposição de coque. O uso de oxigênio diminuiu a produção de coque sobre os catalisadores Co/Al2O3 e Co/SiO2. / In this work Co/Al2O3 and Co/SiO2 catalysts were prepared by impregnation with metal load between 4,0% and 20,0% and were evaluated in the reactions of ethanol steam reforming and ethanol oxidative reforming to study the catalytic stability and the hydrogen yield. Atomic absorption, X-ray powder diffraction, Raman spectroscopy, temperature programmed reduction, nitrogen fisisorption and elemental analysis of carbon were applied to describe the physical and chemical characteristics of these catalysts. The characterization of the catalysts showed the Co3O4 phase and interactions of cobalt species with the support. It was evidenced that only Co0 sites are active for the steam reforming and oxidative reforming of ethanol. The production of hydrogen was about 50-70% and CO was 0- 10%. A high metallic load gave less carbon monoxide production. In the reactions, 2,7-12,7(mg.h-1) of carbon was deposited on all catalysts, indicating that the deactivation of the materials is due to coke deposition. The use of oxygen decreases the production of carbon on the catalysts Co/Al2O3 and Co/SiO2.

A utilização de combustíveis fósseis é um problema a ser contornado visto que sua utilização gera problemas ambientais tais como o aumento do efeito estufa. Como combustível alternativo, ganha destaque o hidrogênio, o qual pode ser utilizado em células à combustível, gerando energia e apenas água como sub-produto. Uma forma de produção de hidrogênio é a partir da reforma a vapor do bio-óleo, proveniente da pirólise da biomassa. Devido à complexidade do bio-óleo, compostos modelo, como o ácido acético e acetol, vêm sendo estudados nos sistemas reacionais. Neste trabalho, estudou-se a reação de reforma a vapor do acetol para obtenção de H2 utilizando-se catalisadores baseados em Ni0 e Co0 derivados de hidróxidos duplos lamelares (HDLs), também chamados de compostos do tipo hidrotalcita. Os HDLs foram sintetizados pelo método de coprecipitação. Análise de difração de raios X (DRX) mostraram a formação dos HDLs e os diferentes teores de Al3+ nas lamelas foram observados através da técnica de espectroscopia na região do infravermelho. Espectroscopia por energia dispersiva de raios X (EDX) indicou que os catalisadores derivados de HDLs calcinados a 750°C possuem quantidades reais de metais ativos próximas aos valores nominais e que possuem diferentes teores de Mg2+. As análises de TPR-H2 mostraram a redução das fases óxidas presentes em altas temperaturas, devido a formação de solução sólida MgNiO2, MgCoO2 e fases espinélios. Nos ensaios catalíticos, catalisadores baseados em Ni0 se mostraram mais seletivos para H2 enquanto que os baseados em Co0 foram mais seletivos para o eteno e compostos líquidos. Ainda, observou-se a tendência de maior seletividade para H2 quanto maior o teor de Mg2+ no catalisador. Para os catalisadores derivados de HDL´s calcinados a 600°C, as caracterizações mostraram resultados semelhantes aos calcinados a 750°C, evidenciando a facilidade de formação das soluções sólida para estes compostos do tipo HDL´s. Para estas amostras também ficou evidenciado que maiores teores de Mg2+ nos catalisadores facilitam a conversão em H2 na reforma a vapor do acetol, o que pode estar associado a propriedade basicidade, que foi quantificada através de termo-dessorção programada de CO2 (TPD-CO2). / The use of fossil fuels is a problem to be circumvented, since its use generates environmental problems such as the increase of the greenhouse effect. As an alternative fuel, hydrogen is highlighted, which can be used in fuel cells, generating energy without the emission of polluting gases. One form of hydrogen production is from the steam reforming of the bio-oil, from the pyrolysis of the biomass. Due to the complexity of the bio-oil, model compounds, present in greater quantity, such as acetic acid and acetol have been studied individually. In this work, the reaction of steam reforming of the acetol to obtain H2 was carried out using catalysts based on Ni0 and Co0 derived from lamellar double hydroxides (HDLs), also called hydrotalcite like compounds. HDLs were synthesized by the coprecipitation method. X-ray diffraction (XRD) analysis showed the formation of HDLs and different Al3+ contents in the lamellae, as well as the Fourier transform infrared spectroscopy technique. X-ray dispersive energy spectroscopy (EDS) has indicated that the catalysts derived from HDLs calcined at 750°C have real amounts of active metals close to the nominal values and that have different levels of Mg2 + and Al3+. The TPR-H2 analysis showed that the reduction of Ni2+ and Co2+ occurs at high temperatures due to the formation of solid solutions MgNiO2, MgCoO2, and spinel phases. In the catalytic tests, Ni2+ based catalysts were more selective for H2, while Co0 based catalysts were more selective for liquid compounds such as acetone. Also, the tendency of greater selectivity for H2 was observed when the Mg2+ content in the catalyst was higher. For the catalysts derived from HDL\'s calcined at 600°C, the characterizations showed results similar to those calcined at 750°C, evidencing the difficult reducibility of oxides derived from HDL\'s. For these catalysts, it was also observed that higher Mg2+ contents facilitate the conversion to H2 in the steam reforming of the acetol, which may be associated with the basicity of the material, which was quantified by means of programmed thermodesorption of CO2 (TPD-CO2).

Oxygen Transport Membranes (OTMs) can drastically reduce the energy and cost demands of processes that require pure oxygen, as they offer the possibility to combine a separation unit with a chemical reactor. One of the most commercially viable applications of OTMs is the partial oxidation of hydrocarbons for syngas production. A typical OTM configuration is a sequential arrangement of layers, i.e. an inactive support, a fuel oxidation layer, a dense layer and an oxygen reduction layer. However, one of the limitations of the OTM system is the low catalytic activity and stability of the materials currently used for the fuel oxidation layer. Moreover, the traditional deposition techniques that are used for the catalysts preparation are difficult to perform, as the fuel oxidation layer is buried deeply in the structure of the OTM. To simplify the OTM fabrication and improve the catalysts activity and stability, this thesis explores the exsolution of Ni nanoparticles from two different host lattice compositions, as potential materials for the fuel oxidation layer of OTMs. The (La₀.₇₅Sr₀.₂₅)(Cr₀.₅Mn₀.₄₅Ni₀.₅)O₃ (LSCMNi5) perovskite was selected, as the first candidate material for the OTMs. During reduction, the exsolution of Ni nanoparticles from the perovskite lattice took place and enhanced significantly the catalytic activity of the material regarding methane conversion. However, these nanoparticles were oxidised during the first hours of the testing and slowly reincorporated into the perovskite structure, leading to drop in the performance. Thereafter, the (La₀.₇₅Sr₀.₂₅)(Cr₀.₅Mn₀.₄₅Ni₀.₅)O₃ (LSCMNi5) perovskite was selected as an alternative composition. When the oxide lattice was sufficiently reduced, the exsolution of Fe-Ni alloy nanoparticles occurred. The catalytic testing suggested that the Fe-Ni alloy nanoparticles on LSCFNi5 presented lower activity for methane conversion comparing to the Ni nanoparticles on LSCMNi5, but higher stability in oxidising conditions. By increasing the Ni doping on the B-site of LSCF to 15 mol%, the catalytic activity of the material regarding methane conversion was increased and exceeded that of LSCMNi5. A CH₄ conversion of 70% was achieved, which was 20 times higher than that of the initial LSCF perovskite. Therefore, by tailoring the perovskite composition and the exsolution of the Fe-Ni alloy nanoparticles, it was possible to synthesize a material for the fuel oxidation layer of OTMs, which combined the high catalytic activity of Ni and the good redox stability of Fe.

The fossil hydrocarbons are not inexhaustible, and their use is not without impact in our need of energy, fuels and hydrocarbons as building blocks for organic materials. The quest for renewable, environmentally more friendly technologies are in need and woody biomass is a promising candidate, well provided in the boreal parts of the world. To convert the constituents of wood into valuable gaseous products, suitable for the end use required, we need a reliable gasification technology. But to become an industrial application on full scale there are still a few issues to take into account since the presence of contaminants in the process gas will pose several issues, both technical and operational, for instance by corrosion, fouling and catalyst deactivation. Furthermore the downstream applications may have very stringent needs for syngas cleanliness depending on its use. Therefore, the levels of contaminants must be decreased by gas cleanup to fulfil the requirements of the downstream applications. One of the most prominent problems in biomass gasification is the formation of tars – an organic byproduct in the degradation of larger hydrocarbons. So, tar degrading catalysts are needed in order to avoid tar related operational problems such as fouling but also reduced conversion efficiency. Deactivation of catalysts is generally inevitable, but the process may be slowed or even prevented. Catalysts are often very sensitive to poisonous compounds in the process gas, but also to the harsh conditions in the gasifier, risking problems as coke formation and attrition. Alongside with having to be resistant to any physical and chemical damage, the catalyst also needs to have high selectivity and conversion rate, which would result in a more or less tar-free gas. Commercial tar reforming catalysts of today often contain nickel as the active element, but also often display a moderate to rapid deactivation due to the causes mentioned.

Actuellement la production d’huile pyrolytique (ou bio-huile) est destinée à en faire un carburant pour les moyens de transport. Cependant, le liquide issu de la pyrolyse est de piètre qualité, il est nécessaire de faire une opération d’hydrodéoxygénation (HDO), très coûteuse et énergivore, pour aboutir à un produit ayant les spécificités d’un carburant. Une des idées proposées, plus économique, consiste à faire de la bio-huile une source de biosyngas (CO+H2) ou biohydrogène renouvelables via du vaporeformage (VR). Ce projet de maitrise étudie le reformage à la vapeur d’eau de deux bio-huiles (MemU et WOU) sans apport externe de vapeur sur un nouveau catalyseur à base de nickel, Ni-UGSO, développé par le GRTP-C à partir du résidu minier UGSO. Les expériences de reformage ont été réalisées à pression atmosphérique, dans un réacteur différentiel et pour une durée de 500 min en faisant varier la température (750-850 °C) et la vélocité spatiale (WHSV= 1.7-7.1 g/gcat/h) en plus d’un test longue durée à 105h. Des tests supplémentaires ont été réalisés aussi avec un catalyseur commercial à titre de comparaison en plus d’un test de régénérabilité. La caractérisation du catalyseur s’est faite par DRX, MEB-FEG, BET et TPR. Les résultats des tests de VR de l’huile MemU entre 750 et 850 °C à WHSV ~1.8 g/gcat/h montrent une bonne production de biosyngas avec une concentration entre 90-95% et une sélectivité en H2 entre 80-95%. Le VR de l’huile WOU dans les mêmes conditions a donné moins de biosyngas et de H2 en raison de la teneur élevée en eau de l’huile. Le catalyseur est resté actif pendant toute la durée des tests, la DRX et la MEB ne montrent aucune trace de carbone. Cependant à WHSV > 6 g/gcat/h du carbone filamenteux sur le catalyseur a été observé par MEB après le VR de l’huile MemU mais pas après le VR de l’huile WOU. La DRX a permis aussi de montrer qu’après le VR des huiles, les oxydes de Fe et Ni qui constituent le catalyseur se réduisent et se combinent pour donner du Ni métallique et des alliages Ni-Fe. Le test BET indique que le catalyseur a une surface spécifique, après activation, de 10 m2/g. La TPR montre qu’il y a plus d’espèces oxydées sur le Ni-UGSO après le VR de la bio-huile WOU qu’après le VR de la bio-huile MemU, d’où les faibles rendements en H2/biosyngas. Les tests de VR réalisés avec le catalyseur commercial montrent des résultats similaires que ceux réalisés avec Ni-UGSO à faible WHSV. Cependant à WHSV élevée le catalyseur commercial a été plus résiliant et plus performant du fait de sa grande surface spécifique. Le test de régénérabilité montre que Ni-UGSO ne peut que partiellement être régénéré et sa structure initiale n’est pas retrouvée Les résultats positifs confirment que la production de biosyngas/biohydrogène par VR de bio-huiles est viable techniquement dans une bioraffinerie. Le procédé est plus économique que l’HDO. De plus, l’huile pyrolytique se trouve être une bonne matière première pour le reformage car on a un bon rendement en biosyngas (ou H2). Le catalyseur Ni-UGSO développé par le GRTP-C a montré des performances similaires que celles de catalyseurs actuellement sur le marché mais nécessite d’être encore optimisé. / Abstract : Currently the production of pyrolysis oil (or bio-oil) is intended to be transformed to transportation fuel. However, the produced liquid is of bad quality and it needs a hydrodeoxygenation (HDO) process which is very expensive and lot of energy is consumed to obtain a final product with the right fuel specifications. One of the ideas proposed, more economical, consists on producing renewable biosyngas (CO+H2) or biohydrogen from biooil by steam reforming (SR). This master project study the steam reforming of two bio-oils (MemU and WOU) without external steam addition over a new nickel based catalyst, Ni-UGSO, developed by the GRTP-C from the mining residue UGSO. The reforming tests were carried out at atmospheric pressure in a differential reactor during 500 min varying the temperature (750- 850 °C) and the weigh hourly space velocity (WHSV= 1.7-7.1 g/gcat/h), a long term test of 105h was also performed. In addition, Supplementary tests were done with a commercial catalyst in order of comparison plus one regenerability test. The catalyst characterization was done by XRD, FEG-SEM, BET and TPR. Test results of bio-oil MemU SR at 750-850 °C and WHSV ~ 1.8 g/gcat/h show a good production of biosyngas with a concentration range of 90-95% and a H2 selectivity of 80- 95%. The SR of bio-oil WOU in the same conditions resulted in less biosyngas and H2 produced because of high water content in the bio-oil. The catalyst was active for the whole duration of tests, XRD and SEM indicate that no carbon deposit was formed. However at WHSV > 6 g/gcat/h filamentous carbon was observed on the catalyst by SEM after the SR of bio-oil MemU but not after the SR of bio-oil WOU. The XRD showed also that after biooils SR Fe and Ni oxides that constitute the catalyst are reduced to metallic Ni and Ni-Fe alloys. BET test indicate that after activation the catalyst has a specific area of 10 m2 /g. TPR shows that more oxidized species are present in Ni-UGSO after bio-oil WOU SR than after bio-oil MemU SR which explains low H2/biosyngas yield. The tests of SR performed with the commercial catalyst show similar results as those performed with Ni-UGSO at low WHSV. However, at high WHSV the commercial catalyst was more resilient and better due to its high specific area. Regenerability test shows that NiUGSO is partially regenerated but its initial structure is not recovered. The positive results confirm that the production of biosyngas/biohydrogen from SR of biooils is technically viable for a biorefinery. The process is economically better than the HDO. The pyrolysis oil is a good feedstock for the reforming, we obtain an appreciable yield of biosyngas (or H2). The catalyst Ni-UGSO developed by the GRTP-C exhibits similar performances than commercial catalysts actually available in the market but needs more optimisation.