Visando a produção de hidrogênio, como uma fonte renovável de energia, estudaram-se as reações de reforma a vapor e oxidativa do etanol sobre catalisadores de Ru/CeO2-Al2O3. Foi verificado o efeito do suporte e das interações metal/suporte sobre a atividade e seletividade para as reações. Os suportes e catalisadores foram caracterizados por fisissorção de nitrogênio pelo método B.E.T., para avaliar as áreas superficiais específicas, espectroscopia dispersiva de raios-X (EDX), para determinar a distribuição qualitativa da fase metálica sobre os suportes, difração de raios-X (DRX), para identificação das fases óxidas, espectroscopia na região do ultra-violeta e do visível (UV-vis NIR), para avaliar as transições eletrônicas presentes no material, e redução a temperatura programada (RTP), para avaliação do comportamento de redução e das fases redutíveis. Através dos ensaios catalíticos, pode-se verificar que todos os catalisadores foram ativos para ambas as reações de reforma, sob as temperaturas de 400, 600 e 700ºC, onde a conversão do etanol aumentou com o aumento da temperatura e com o aumento da adição de CeO2 ao suporte catalítico. O catalisador 3%Ru/CeO2 foi o mais ativo frente a reação de reforma a vapor e o 3%Ru/25%CeO2-Al2O3 o catalisador mais ativo para a reação de reforma oxidativa do etanol. A maior seletividade para H2 foi obtida a 600ºC para ambas as reações de reforma, com exceção dos catalisadores 3%Ru/20%CeO2-Al2O3, que foi mais seletivo a 700ºC para a reforma a vapor, e 3%Ru/CeO2, que foi mais seletivo a 400ºC para a reforma oxidativa. / Aiming at hydrogen production, as a source of renewable energy, Ru/CeO2-Al2O3 catalysts were studied in ethanol steam reform and ethanol oxidative reforming. The effect of the support and metal/support interaction was verified on the activity and selectivity of the reactions. The supports and catalysts were characterized by x-rays dispersive spectroscopy (XDS), to verify the qualitative distribution of the metallic phase on the supports, x-rays diffraction (XRD), for identification of the crystalline oxide phases, spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR), to evaluate the electronic transitions present in the material, and temperature programmed reduction (TPR), for evaluation of the reductive phases. According to the catalytic tests, all catalysts were active for both reactions under the temperatures of 400, 600 and 700ºC, where the ethanol conversion increased together with the increase of the temperature and, with the addition of CeO2 to the catalytic support. The 3%Ru/CeO2 catalyst was the most active for ethanol steam reforming and the 3%Ru/25%CeO2-Al2O3 catalyst was the most active for ethanol oxidative reforming. The higher selectivity for H2 occurred at 600ºC for both reactions, excluding the 3%Ru/20%CeO2-Al2O3 catalyst, which was more selective at 700ºC for steam reforming, and the 3%Ru/CeO2 catalyst, which was more selective for the oxidative reforming at 400ºC.

As a means to produce high pressure hydrogen in order to reduce compression penalty, we propose to reform liquid fuel (e.g., bio-ethanol) in supercritical water (pressure above 221 bar and temperature greater than 374°C). Catalytic ethanol reforming in supercritical water for hydrogen production has been carried out in a high pressure packed bed reactor made of Inconel-625. Since Inconel-625 contains mainly nickel, it is expected that the reactor itself can be active toward ethanol reforming. Therefore, a series of tests were first performed in the empty reactor, whose results are a benchmark when studying reforming in the presence of a catalyst. Ethanol reforming in the empty reactor was studied in the temperature range of 450 to 600°C and showed coking/plugging problem at 575°C and above. The ethanol conversion with the empty reactor could be as high as 25% at 550°C and residence time of about one minute. The main reaction products with the empty reactor were H2, CO and CH4. A catalyst screening study was performed to investigate the performance of nickel and cobalt as active metals, supported on γ-Al2O3, α-Al2O3, ZrO2 and YSZ for temperatures between 475°C and 550°C. The presence of the catalyst did increase the activity of ethanol reforming, especially at higher temperatures. All experiments in the catalyst screening study were carried out with non-reduced catalysts. Nickel catalysts were found more active than cobalt, likely because of higher reducibility. Indeed, the higher amount of oxygen in Co3O4 compared to NiO requires more hydrogen to fully reduce the metal oxides. Both Ni/γ-Al2O3 and Co/γ-Al2O3 showed little activity below 500°C, and led to failed experiments due to coking/plugging at temperatures of 525°C and above. The strong acid sites on γ-Al2O3 are responsible for high selectivity toward ethylene, a known coke precursor. The support α-Al2O3 in combination with Ni was active, but yielded lower H2 selectivity and higher CH4 selectivity than the zirconia-based catalysts. The Co/α-Al2O3 shows low activity. The ZrO2-based catalysts were active and yielded high H2 selectivity, but were found very fragile. Finally, the YSZ support was strong and yielded good conversion. Below 550°C the activity of Ni/YSZ is higher than that of Co/YSZ, but at 550°C both catalysts yield nearly complete conversion. The advantage of Co/YSZ is then higher H2 selectivity and lower CH4 selectivity compared to Ni/YSZ. Therefore, Co/YSZ was selected for a more detailed study. The effect of temperature, flowrate, residence time, catalyst weight, Co loading, concentration, and pretreatment with H2 were considered. Two methods for catalyst reduction were applied: ex-situ reduction where the catalyst is reduced in a different reactor and in-situ reduction where the catalyst is reduced in the SCW reactor prior to ethanol reforming. At 550°C, Co/YSZ converts all ethanol for residence times as low as 2 s, even with non-reduced catalyst. At 500°C the activity of the in-situ and ex-situ reduced catalysts were similar and greater than for the non-reduced catalyst. At 475°C the ex-situ reduced catalyst showed low activity, comparable to that of the non-reduced catalyst, but the in-situ reduced catalyst yielded much higher conversion. The better performance of the in-situ reduced catalyst was attributed to active metal sites on the reactor’s wall after pre-treatment in H2. The low activity of the ex-situ reduced catalyst is due to the fact that, when exposed to supercritical water for less than 30 minutes, it re-oxidized to CoO. The temperature of 475°C is then too low to generate sufficient hydrogen that will start reducing the catalyst. Finally, analysis of reaction pathways for ethanol reforming over Co/YSZ showed that the reaction proceeds mostly via ethanol dehydrogenation to form acetaldehyde, the latter species reacting with lattice oxygen on the catalyst to produce acetone and CO2. Acetone is then reformed by water into CO and H2. Finally, H2 and CO react via the methanation reaction to form CH4. Over Co/YSZ it was found that the water-gas shift reaction is fast (CO selectivity most of the time is less than 0.5%), but the methanation reaction is kinetically controlled. Stopping the methanation reaction before equilibrium allowed for H2 selectivity higher than what is expected at equilibrium (likewise, CH4 selectivity is smaller than equilibrium value). For well-controlled reaction Co/YSZ is a promising catalyst that can be highly selective toward hydrogen during ethanol reforming in supercritical water.

As a means to produce high pressure hydrogen in order to reduce compression penalty, we propose to reform liquid fuel (e.g., bio-ethanol) in supercritical water (pressure above 221 bar and temperature greater than 374°C). Catalytic ethanol reforming in supercritical water for hydrogen production has been carried out in a high pressure packed bed reactor made of Inconel-625. Since Inconel-625 contains mainly nickel, it is expected that the reactor itself can be active toward ethanol reforming. Therefore, a series of tests were first performed in the empty reactor, whose results are a benchmark when studying reforming in the presence of a catalyst. Ethanol reforming in the empty reactor was studied in the temperature range of 450 to 600°C and showed coking/plugging problem at 575°C and above. The ethanol conversion with the empty reactor could be as high as 25% at 550°C and residence time of about one minute. The main reaction products with the empty reactor were H2, CO and CH4. A catalyst screening study was performed to investigate the performance of nickel and cobalt as active metals, supported on γ-Al2O3, α-Al2O3, ZrO2 and YSZ for temperatures between 475°C and 550°C. The presence of the catalyst did increase the activity of ethanol reforming, especially at higher temperatures. All experiments in the catalyst screening study were carried out with non-reduced catalysts. Nickel catalysts were found more active than cobalt, likely because of higher reducibility. Indeed, the higher amount of oxygen in Co3O4 compared to NiO requires more hydrogen to fully reduce the metal oxides. Both Ni/γ-Al2O3 and Co/γ-Al2O3 showed little activity below 500°C, and led to failed experiments due to coking/plugging at temperatures of 525°C and above. The strong acid sites on γ-Al2O3 are responsible for high selectivity toward ethylene, a known coke precursor. The support α-Al2O3 in combination with Ni was active, but yielded lower H2 selectivity and higher CH4 selectivity than the zirconia-based catalysts. The Co/α-Al2O3 shows low activity. The ZrO2-based catalysts were active and yielded high H2 selectivity, but were found very fragile. Finally, the YSZ support was strong and yielded good conversion. Below 550°C the activity of Ni/YSZ is higher than that of Co/YSZ, but at 550°C both catalysts yield nearly complete conversion. The advantage of Co/YSZ is then higher H2 selectivity and lower CH4 selectivity compared to Ni/YSZ. Therefore, Co/YSZ was selected for a more detailed study. The effect of temperature, flowrate, residence time, catalyst weight, Co loading, concentration, and pretreatment with H2 were considered. Two methods for catalyst reduction were applied: ex-situ reduction where the catalyst is reduced in a different reactor and in-situ reduction where the catalyst is reduced in the SCW reactor prior to ethanol reforming. At 550°C, Co/YSZ converts all ethanol for residence times as low as 2 s, even with non-reduced catalyst. At 500°C the activity of the in-situ and ex-situ reduced catalysts were similar and greater than for the non-reduced catalyst. At 475°C the ex-situ reduced catalyst showed low activity, comparable to that of the non-reduced catalyst, but the in-situ reduced catalyst yielded much higher conversion. The better performance of the in-situ reduced catalyst was attributed to active metal sites on the reactor’s wall after pre-treatment in H2. The low activity of the ex-situ reduced catalyst is due to the fact that, when exposed to supercritical water for less than 30 minutes, it re-oxidized to CoO. The temperature of 475°C is then too low to generate sufficient hydrogen that will start reducing the catalyst. Finally, analysis of reaction pathways for ethanol reforming over Co/YSZ showed that the reaction proceeds mostly via ethanol dehydrogenation to form acetaldehyde, the latter species reacting with lattice oxygen on the catalyst to produce acetone and CO2. Acetone is then reformed by water into CO and H2. Finally, H2 and CO react via the methanation reaction to form CH4. Over Co/YSZ it was found that the water-gas shift reaction is fast (CO selectivity most of the time is less than 0.5%), but the methanation reaction is kinetically controlled. Stopping the methanation reaction before equilibrium allowed for H2 selectivity higher than what is expected at equilibrium (likewise, CH4 selectivity is smaller than equilibrium value). For well-controlled reaction Co/YSZ is a promising catalyst that can be highly selective toward hydrogen during ethanol reforming in supercritical water.

Visando a produção de hidrogênio, como uma fonte renovável de energia, estudaram-se as reações de reforma a vapor e oxidativa do etanol sobre catalisadores de Ru/CeO2-Al2O3. Foi verificado o efeito do suporte e das interações metal/suporte sobre a atividade e seletividade para as reações. Os suportes e catalisadores foram caracterizados por fisissorção de nitrogênio pelo método B.E.T., para avaliar as áreas superficiais específicas, espectroscopia dispersiva de raios-X (EDX), para determinar a distribuição qualitativa da fase metálica sobre os suportes, difração de raios-X (DRX), para identificação das fases óxidas, espectroscopia na região do ultra-violeta e do visível (UV-vis NIR), para avaliar as transições eletrônicas presentes no material, e redução a temperatura programada (RTP), para avaliação do comportamento de redução e das fases redutíveis. Através dos ensaios catalíticos, pode-se verificar que todos os catalisadores foram ativos para ambas as reações de reforma, sob as temperaturas de 400, 600 e 700ºC, onde a conversão do etanol aumentou com o aumento da temperatura e com o aumento da adição de CeO2 ao suporte catalítico. O catalisador 3%Ru/CeO2 foi o mais ativo frente a reação de reforma a vapor e o 3%Ru/25%CeO2-Al2O3 o catalisador mais ativo para a reação de reforma oxidativa do etanol. A maior seletividade para H2 foi obtida a 600ºC para ambas as reações de reforma, com exceção dos catalisadores 3%Ru/20%CeO2-Al2O3, que foi mais seletivo a 700ºC para a reforma a vapor, e 3%Ru/CeO2, que foi mais seletivo a 400ºC para a reforma oxidativa. / Aiming at hydrogen production, as a source of renewable energy, Ru/CeO2-Al2O3 catalysts were studied in ethanol steam reform and ethanol oxidative reforming. The effect of the support and metal/support interaction was verified on the activity and selectivity of the reactions. The supports and catalysts were characterized by x-rays dispersive spectroscopy (XDS), to verify the qualitative distribution of the metallic phase on the supports, x-rays diffraction (XRD), for identification of the crystalline oxide phases, spectroscopy in the region of the ultraviolet and the visible (UV-vis NIR), to evaluate the electronic transitions present in the material, and temperature programmed reduction (TPR), for evaluation of the reductive phases. According to the catalytic tests, all catalysts were active for both reactions under the temperatures of 400, 600 and 700ºC, where the ethanol conversion increased together with the increase of the temperature and, with the addition of CeO2 to the catalytic support. The 3%Ru/CeO2 catalyst was the most active for ethanol steam reforming and the 3%Ru/25%CeO2-Al2O3 catalyst was the most active for ethanol oxidative reforming. The higher selectivity for H2 occurred at 600ºC for both reactions, excluding the 3%Ru/20%CeO2-Al2O3 catalyst, which was more selective at 700ºC for steam reforming, and the 3%Ru/CeO2 catalyst, which was more selective for the oxidative reforming at 400ºC.

Lithium orthosilicate (Li4SiO4) is known to be a high temperature CO2 capture material. This work was focused on comparing Li4SiO4 to the extensively studied CaO as an adsorbent in sorption enhanced catalysis. Thermogravimetric analysis was used to study the effects of sorption temperature and compaction on Li4SiO4 using 15vol% CO2 in N2. After 2 hours of CO2 adsorption at 550°C the powder reached 35wt% uptake of CO2, corresponding to 93.6% of maximum efficiency and complete regeneration was possible at 700°C. Pressing Li4SiO4 to granular forms greatly decreased CO2 adsorption rates. Efforts to impregnate -Al2O3 with the suspended SiO2 solution from aqueous based sol-gel synthesis to produce nanodispersed Li4SiO4 failed due to the inability to form the targeted Li4SiO4 complex. X-ray diffraction analysis indicated the formation of the gel is crucial for the formation of the crystalline Li4SiO4 phase. A microreactor was used to study the steam reforming of ethanol over a series of 1% Pt on -Al2O3 catalyst composite impregnated over a range of nanodispersed CaO loading at S/C=1.5 in dilution. At 400°C enhancement could be observed with the presence of CaO sorbent compared to only 1% Pt/Al2O3. However, production quickly diminished due to high carbon deposition. For 1% Pt/Al2O3 tested at 400°C, ethylene production was 5 times higher than for hydrogen. Above 550°C the ethylene production was reduced to 0.18vol% and gas production stability was greatly improved for 1% Pt/Al2O3 and even more so with the addition of impregnated CaO sorbent. Hydrogen yields from homogeneous mixtures of 1%Pt/Al2O3 with Li4SiO4 powder in a microreactor were about 20% higher than those achievable of the same mixture with CaO powder. However, the composite 1%Pt/Al2O3 with 7.02wt% dispersed CaO gave 100% higher hydrogen production under similar conditions despite Li4SiO4 being a superior carbon capture material. / Litiumortosilikat (Li4SiO4) är ett känt CO2 adsorptionsmaterial vid höga temperaturer. Fokuset i detta arbete var att jämföra Li4SiO4 med det välstuderade CaO som adsorbent i adsorptionsförbättrad katalys. Termogravimetrisk analys användes för att studera effekten av temperatur och kompaktering på Li4SiO4 med 15vol% CO2 i balanserad N2. Efter 2 timmars CO2 adsorption vid 550°C hade pulvret nått 35vikt% ökning av CO2, vilket korresponderar till 93.6% av den maximala verkningsgraden. Dessutom var fullständig regenerering möjlig vid 700°C. Pressad Li4SiO4 i grynig form sänkte CO2 adsorptionshastigheten signifikant. Försök att impregnera -Al2O3 med suspenderad SiO2 från en vattenbaserad sol-gel metod för att bilda nanodispergerad Li4SiO4 misslyckades på grund av oförmågan att bilda önskade Li4SiO4 komplex. Röntgendiffraktions analys tydde på att bildningen av gelen var avgörande för bildningen av en kristallin Li4SiO4 fas. En mikroreaktor användes för att studera ångreformeringen av etanol hos 1% Pt på - Al2O3 katalysator komposit impregnerad med ett varierande tillskott av nanodispergerad CaO i utspädd S/C=1.5. Vid 400°C kunde en förbättring observeras då CaO var närvarande jämfört med endast 1% Pt/Al2O3. Dock minskade gasproduktionen kraftigt på grund av hög koksning. Tester på 1% Pt/Al2O3 vid 400°C visade att eten produktionen var 5 gånger högre än för vätgasproduktionen. Över 550°C sjunkte eten produktionen till 0.18vol% och gas produktionsstabiliteten förbättrades signifikant för 1% Pt/Al2O3 och även bättre i närvaro av nanodispergerad CaO. Vätgasutbytet från en homogen blandning av 1% Pt/Al2O3 med Li4SiO4 pulver i en mikroreaktor var 20% högre än det som åstadkoms för samma blandning med med CaO pulver. Dock visade 1%Pt/Al2O3 med 7.02vikt% dispergerad CaO 100% högre vätgasproduktion under liknande förhållanden trots att Li4SiO4 är en överlägsen koluppfångar material.

Neste trabalho foram preparados e caracterizados catalisadores de cobalto suportados em y-Al2O3, CeO2, 20%CeO2-yAl2O3 e em soluções sólidas CexZr1-xO2 (0<= x<=1), pelo método de impregnação, com o objetivo de avaliar o desempenho destes frente à reforma a vapor e oxidativa do etanol. Na preparação dos catalisadores utilizou-se o teor de 20% em massa de cobalto, para os suportes y-Al2O3, CeO2 e 20%CeO2-y-Al2O3, e 10% para os suportes CexZr1-xO2. Para a caracterização dos sólidos, as técnicas utilizadas foram: Espectroscopia Dispersiva de Raios-X (EDX), Redução a Temperatura Programada com H2 (RTP-H2), Difração de Raios-X pelo método do pó (DRX), Adsorção de Nitrogênio pelo método B.E.T. e Espectroscopia na região do Ultravioleta e do Visível. As reações de reforma a vapor de etanol foram realizadas nas temperaturas de 400, 500 e 600oC com razões molares H2O/Etanol= 3/1 e 4/1. Já, os ensaios catalíticos de reforma oxidativa foram realizados a 500oC com razões molares H2O/Etanol/O2= 3/1/0,16 e 3/1/0,20. Através dos resultados de DRX e RTP-H2 verificou-se a formação da fase Co3O4 para todos os catalisadores. Para os catalisadores suportados em y-Al2O3 e 20%CeO2-y Al2O3 observou-se ainda a formação da fase CoO-Al2O3. Nos ensaios catalíticos de reforma a vapor do etanol foi verificado que as mais altas conversões do etanol em produtos e maiores seletividades a hidrogênio foram obtidas a 600oC e razão H2O/Etanol=3/1. A maior razão CO2/CO foi obtida a 500oC com o catalisador Co/Ce0,4Zr0,6O2. Observou-se também que a adição de oxigênio ocasionou uma diminuição na deposição de carbono. / Cobalt supported in yAl2O3, CeO2, 20%CeO2-yAl2O3 and CexZr1-xO2 (0<= x <= 1) solid solution, were prepared by impregnation and applied in steam and oxidative reforming of ethanol. In the preparation of the catalysts was used 20wt.% of cobalt with yAl2O3, CeO2 and 20%CeO2-yAl2O3 supports and 10wt.% with CexZr1-xO2 supports. The solids were characterized by X-Ray Dispersive Spectroscopy; Temperature Programmed of Reduction with H2 (TPR- H2); X-Ray Diffraction (XRD); Nitrogen Adsorption by B.E.T. method; Ultraviolet and Visible Spectroscopy. The ethanol steam reforming was carried out at 400, 500 and 600oC with molar rates H2O/Ethanol= 3/1 and 4/1. The ethanol oxidative reforming was carried out at 500 °C with molar rates H2O/Ethanol/O2 = 3/1/0.16 e 3/1/0.20. XRD and TPR-H2 results showed the formation of Co3O4 phase for all catalysts. For the catalysts supported in y-Al2O3 and 20%CeO2-y-Al2O3 was still observed the formation of the CoO-Al2O3 phase. In the ethanol steam reforming the higher conversion was obtained at 600°C and the best H2 selectivity was observed with the H2O/Etanol=3/1 molar ratio. The higher CO2/CO ratio was observed at 500oC with Co/Ce0,4Zr0,6O2 catalyst. Already, the addition of oxygen caused a decrease in the carbon deposition.

Pesquisas realizadas em todo o mundo exploram a possibilidade de utilizar o hidrogênio como combustível para a geração de energia, já que ele produz a chamada \"energia limpa\". O hidrogênio pode ser obtido a partir das reações de reforma de etanol, fonte renovável, em contraste com o clássico processo de obtenção a partir de derivados de petróleo. Desta forma, há um crescente interesse em pesquisa e desenvolvimento de catalisadores eficientes para gerar hidrogênio. Assim, no presente trabalho foram estudados catalisadores de ródio contendo 0,5; 1 e 3% (m/m) suportados em CeO2, Al2O3 e 20%CeO2- Al2O3 nas reações de reforma a vapor de etanol (RVE) e reforma oxidativa de etanol (ROE) visando a geração de hidrogênio. As amostras foram preparadas pelo método de impregnação úmida e caracterizadas por difração de Raios-X (XRD), área superficial específica - método B.E.T., espectroscopia dispersiva em emissão de Raios-X (EDX), espectroscopia de fotoelétrons excitada por Raios-X (XPS), espectroscopia na região do ultra-violeta e do visível (UV-vis- NIR) e redução à temperatura programada (RTP-H2). Os ensaios catalíticos, realizados entre 400 e 600ºC, mostraram altas conversões de etanol para todos os catalisadores. As maiores produções de H2, a partir das reações de RVE e ROE, foram obtidas à 600ºC com os catalisadores Rh/CeO2 e Rh/20%CeO2-Al2O3. Foi observado que a adição de oxigênio proporcionou um aumento na produção de H2, bem como na razão CO2/CO e nas deposições de carbono. / The researches made in the world explore the possibility in the use of hydrogen like a fuel for energy generation, since it produces the called \"clean energy\". The hydrogen can be obtained through of the ethanol reforming reaction, i.e. renewable source, in contrast with the classical process for obtaining from petroleum derivates. In this way, there is a crescent interest in research and development of efficient catalysts in order to obtain hydrogen. Thus, in this work were studied the rodium catalysts with 0,5; 1 e 3% (w/w) supported on CeO2, Al2O3 e 20%CeO2-Al2O3 for the ethanol steam reforming (ESR) and oxidative reforming (EOR) reactions aiming to the hydrogen generation. The samples were prepared by wet impregnation method and characterized by X-ray diffraction (XRD), specific superficial area - BET method, energy dipersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy (UVvis), and temperature-programmed reduction (TPR-H2). In according to the catalytic tests, performed between 400 and 600ºC, it was obtained higher ethanol conversion values for all catalysts. The highest H2 yield it was obtained at 600ºC, with the Rh/CeO2 e Rh/20%CeO2-Al2O3 catalysts. It was observed that the addition of oxygen caused an increase in H2 production, as well as, in the CO2/CO ratio and in the carbon deposition.

Neste trabalho foram preparados e caracterizados catalisadores de cobalto suportados em y-Al2O3, CeO2, 20%CeO2-yAl2O3 e em soluções sólidas CexZr1-xO2 (0<= x<=1), pelo método de impregnação, com o objetivo de avaliar o desempenho destes frente à reforma a vapor e oxidativa do etanol. Na preparação dos catalisadores utilizou-se o teor de 20% em massa de cobalto, para os suportes y-Al2O3, CeO2 e 20%CeO2-y-Al2O3, e 10% para os suportes CexZr1-xO2. Para a caracterização dos sólidos, as técnicas utilizadas foram: Espectroscopia Dispersiva de Raios-X (EDX), Redução a Temperatura Programada com H2 (RTP-H2), Difração de Raios-X pelo método do pó (DRX), Adsorção de Nitrogênio pelo método B.E.T. e Espectroscopia na região do Ultravioleta e do Visível. As reações de reforma a vapor de etanol foram realizadas nas temperaturas de 400, 500 e 600oC com razões molares H2O/Etanol= 3/1 e 4/1. Já, os ensaios catalíticos de reforma oxidativa foram realizados a 500oC com razões molares H2O/Etanol/O2= 3/1/0,16 e 3/1/0,20. Através dos resultados de DRX e RTP-H2 verificou-se a formação da fase Co3O4 para todos os catalisadores. Para os catalisadores suportados em y-Al2O3 e 20%CeO2-y Al2O3 observou-se ainda a formação da fase CoO-Al2O3. Nos ensaios catalíticos de reforma a vapor do etanol foi verificado que as mais altas conversões do etanol em produtos e maiores seletividades a hidrogênio foram obtidas a 600oC e razão H2O/Etanol=3/1. A maior razão CO2/CO foi obtida a 500oC com o catalisador Co/Ce0,4Zr0,6O2. Observou-se também que a adição de oxigênio ocasionou uma diminuição na deposição de carbono. / Cobalt supported in yAl2O3, CeO2, 20%CeO2-yAl2O3 and CexZr1-xO2 (0<= x <= 1) solid solution, were prepared by impregnation and applied in steam and oxidative reforming of ethanol. In the preparation of the catalysts was used 20wt.% of cobalt with yAl2O3, CeO2 and 20%CeO2-yAl2O3 supports and 10wt.% with CexZr1-xO2 supports. The solids were characterized by X-Ray Dispersive Spectroscopy; Temperature Programmed of Reduction with H2 (TPR- H2); X-Ray Diffraction (XRD); Nitrogen Adsorption by B.E.T. method; Ultraviolet and Visible Spectroscopy. The ethanol steam reforming was carried out at 400, 500 and 600oC with molar rates H2O/Ethanol= 3/1 and 4/1. The ethanol oxidative reforming was carried out at 500 °C with molar rates H2O/Ethanol/O2 = 3/1/0.16 e 3/1/0.20. XRD and TPR-H2 results showed the formation of Co3O4 phase for all catalysts. For the catalysts supported in y-Al2O3 and 20%CeO2-y-Al2O3 was still observed the formation of the CoO-Al2O3 phase. In the ethanol steam reforming the higher conversion was obtained at 600°C and the best H2 selectivity was observed with the H2O/Etanol=3/1 molar ratio. The higher CO2/CO ratio was observed at 500oC with Co/Ce0,4Zr0,6O2 catalyst. Already, the addition of oxygen caused a decrease in the carbon deposition.

Pesquisas realizadas em todo o mundo exploram a possibilidade de utilizar o hidrogênio como combustível para a geração de energia, já que ele produz a chamada \"energia limpa\". O hidrogênio pode ser obtido a partir das reações de reforma de etanol, fonte renovável, em contraste com o clássico processo de obtenção a partir de derivados de petróleo. Desta forma, há um crescente interesse em pesquisa e desenvolvimento de catalisadores eficientes para gerar hidrogênio. Assim, no presente trabalho foram estudados catalisadores de ródio contendo 0,5; 1 e 3% (m/m) suportados em CeO2, Al2O3 e 20%CeO2- Al2O3 nas reações de reforma a vapor de etanol (RVE) e reforma oxidativa de etanol (ROE) visando a geração de hidrogênio. As amostras foram preparadas pelo método de impregnação úmida e caracterizadas por difração de Raios-X (XRD), área superficial específica - método B.E.T., espectroscopia dispersiva em emissão de Raios-X (EDX), espectroscopia de fotoelétrons excitada por Raios-X (XPS), espectroscopia na região do ultra-violeta e do visível (UV-vis- NIR) e redução à temperatura programada (RTP-H2). Os ensaios catalíticos, realizados entre 400 e 600ºC, mostraram altas conversões de etanol para todos os catalisadores. As maiores produções de H2, a partir das reações de RVE e ROE, foram obtidas à 600ºC com os catalisadores Rh/CeO2 e Rh/20%CeO2-Al2O3. Foi observado que a adição de oxigênio proporcionou um aumento na produção de H2, bem como na razão CO2/CO e nas deposições de carbono. / The researches made in the world explore the possibility in the use of hydrogen like a fuel for energy generation, since it produces the called \"clean energy\". The hydrogen can be obtained through of the ethanol reforming reaction, i.e. renewable source, in contrast with the classical process for obtaining from petroleum derivates. In this way, there is a crescent interest in research and development of efficient catalysts in order to obtain hydrogen. Thus, in this work were studied the rodium catalysts with 0,5; 1 e 3% (w/w) supported on CeO2, Al2O3 e 20%CeO2-Al2O3 for the ethanol steam reforming (ESR) and oxidative reforming (EOR) reactions aiming to the hydrogen generation. The samples were prepared by wet impregnation method and characterized by X-ray diffraction (XRD), specific superficial area - BET method, energy dipersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), UV-vis spectroscopy (UVvis), and temperature-programmed reduction (TPR-H2). In according to the catalytic tests, performed between 400 and 600ºC, it was obtained higher ethanol conversion values for all catalysts. The highest H2 yield it was obtained at 600ºC, with the Rh/CeO2 e Rh/20%CeO2-Al2O3 catalysts. It was observed that the addition of oxygen caused an increase in H2 production, as well as, in the CO2/CO ratio and in the carbon deposition.

L’alumine est un support important en catalyse hétérogène. Le contrôle de ses propriétés physiques et texturales permet d’en améliorer les performances comme support pour des applications en catalyse. Les catalyseurs à base de cobalt sont connus pour présenter d’excellentes performances pour la réaction de reformage de l’éthanol (RRE) du fait de leur grande affinité à cliver les liaisons C-H et C-C.De nombreuses études ont visé à corréler les propriétés de l’alumine avec celles des catalyseurs. L’alumine présente une chimie de surface plutôt complexe qui peut être contrôlée par le mode de préparation. Dans ce travail,des alumines possédant des méso- et macropores ont été obtenues par voie sol-gel dans un mode de préparation « one-pot » accompagnée par une séparation de phases. Dans cette stratégie intégrative, les deux procédés,gélification et séparation de phases, surviennent spontanément dans les systèmes contenant un inducteur de séparation de phase.Les différentes alumines ont été synthétisées à partir d’isopropoxyde oude chlorure d’aluminium et de polyethylène oxyde ou polypropylène oxydeutilisés comme inducteur de séparation de phases. Le choix approprié des compositions des réactifs permet le contrôle de la taille et volume des pores. La formation des macropores résulte du processus de séparation de phase après décomposition par calcination de l’inducteur alors que l’espace entre particules formant le squelette du xerogel constitue la structure mésoporeuse.Les différentes alumines poreuses ainsi préparées et une alumine commerciale ont été utilisées comme supports de catalyseurs de cobalt par imprégnation par voie humide. Les précurseurs oxydes du catalyseur obtenu après calcination sont composés de phases de type Co ₃ O ₄ et CoAl₂O ₄ , cette dernière étant en quantité plus importante dans les alumines synthétiques.Comme les alumines sol-gel sont caractérisées par une plus grande proportion d’aluminium en site octaédrique et de groupement hydroxyles de surface que l’alumine commerciale, nous avons proposé que ces caractéristiques facilitent la migration du Cobalt dans le réseau alumine et explique la formation plus importante de phase de type CoAl₂O ₄ .Les catalyseurs ont été caractérisés pendant l’activation et en conditions réelles de fonctionnement RRE par EXAFS rapide pour suivre l’évolution de l’ordre local du cobalt et par spectroscopie Raman et spectrométrie de masse résolues dans le temps pour l’analyse des produits de réaction. Si l’espèce active est indiscutablement Co0, nous avons montré que les performances catalytiques dépendent aussi du rapport Co ² ⁺ /Co ⁰ obtenu après activation, dans le sens où de faibles rapports Co ² ⁺ /Co ⁰ ne permettront pas de nettoyer la surface du catalyseur par oxydation du coke formé lorsque la réaction de reformage de l’éthanol opère. Une conclusion importante de ce travail est la mise en évidence du rôle joué par l’oxyde cobalt (CoO) dans la stabilité du catalyseur à travers la promotion de l’oxydation des espèces carbonées déposées en surface. Ainsi le contrôle du rapport Co ² ⁺ /Co ⁰ apparaît comme un élément capital pour la conception de catalyseurs performants à base de cobalt pour la réaction de reformage de l’éthanol, le choix du support étant essentiel / Alumina is an important support for heterogeneous catalysts. Thematching of appropriate alumina physical properties and controlled texturalproperties can improve its performance as support in catalysis applications.Cobalt based catalysts have been reported to have a good ethanol steamreforming (ESR) performance due to their high activity for the cleavage of C-Hand C-C bonds.Many studies have been conducted about the effects of aluminaproperties on the cobalt catalysts properties. Alumina exhibits a rather complexsurface chemistry which can be controlled by the preparation procedure. In thiswork alumina samples with macro and mesoporous structure were obtainedusing the one-pot sol-gel synthesis accompanied by phase separation. In thisintegrative strategy both processes, gelation and phase separation,spontaneously occur in system containing the presence of the phase separationinducer.The different aluminas were produced by using as aluminum reactants,aluminum isopropoxide and chloride and PolyEthylene Oxide or PolyPropyleneOXide as phase separation inducer. Appropriate choice of the startingcomposition allows the control the pore size and volume. Macroporous areformed as a result of phase separation after burning the phase separationinducer, while voids between particles of the xerogel skeletons form amesoporous structures.The different alumina porous alumina and commercial alumina wereused as supports for preparing by wetness impregnation cobalt-based catalyst.The oxidic catalyst precursors obtained after calcination are composed of Co ₃ O ₄ and CoAl₂O ₄ -like phases, the latter being in higher proportions in the sol-gelalumina than in the commercial one. As the sol-gel alumina presents a largeramount of octahedral AlVI sites and surface hydroxyl groups than thecommercial alumina, it was assumed that these features can facilitate themigration of Co ions into the alumina network leading to formation of thegreatest amount of CoAl₂O ₄ .The catalysts were characterized under realistic activation and reactionconditions by the combination of Quick-XAS (X-ray Absorption Spectroscopy)for monitoring the change of the local order around Co with time-resolvedRaman and Mass spectroscopy for monitoring reaction products. If the Co(0)species is undoubtedly the active species for ESR, the catalytic performancehas been clearly shown to be affected by the Co ² ⁺ /Co ⁰ ratio obtained afteractivation, getting lower Co ² ⁺ /Co ⁰ ratios will not allow to clean the surface of thecatalyst by oxidation of C* as ESR is running. As an important conclusion of thework reported herein, we have evidenced that the cobalt oxide (CoO) plays akey role in the stability over time of the catalyst through oxidation of adsorbedand reactive carbon atoms. Then the control of the Co ²⁺ /Co ⁰ ratio appears to beone of the key issues in the design of efficient cobalt alumina-supported ethanolsteam reforming catalysts and the choice of the support is essential forcontrolling this ratio of active cobalt species.