Neste trabalho foram preparados e caracterizados catalisadores de platina suportados em g-alumina (g-Al2O3), óxido de zircônio (ZrO2) e em suportes mistos de óxido de zircônio e g-alumina. Os suportes bi-componente contendo (15%) ZrO2/g-Al2O3 foram preparados por dois métodos distintos: no primeiro, utilizou-se uma suspensão ácida de óxido de zircônio comercial e no segundo, óxido de zircônio precipitado a partir do acetato. Os catalisadores foram submetidos a ensaios catalíticos de reforma a vapor de etanol a fim de verificar o efeito do suporte sobre a distribuição dos produtos. As técnicas de caracterização utilizadas foram área superficial específica (B.E.T), redução a temperatura programada (RTP), difração de raios-X (DRX) e espectroscopia de absorção molecular na região UV-VI, que identificou a espécie [PtOxCly]s2-. A conversão do etanol e a distribuição dos produtos variaram para cada suporte testado e para os diferentes tempos de contatos (W/F) utilizados. O catalisador (1%) Pt/g-Al2O3 apresentou a melhor seletividade para a produção de hidrogênio e a menor conversão para o etanol. Os catalisadores que utilizaram o suporte bi-componente (15%) ZrO2/g-Al2O3 e ZrO2 pura apresentaram alta conversão de etanol e baixa seletividade para hidrogênio, além de alta tendência à formação de bio-produtos. / In this work catalysts of platinum supported on g-alumina (g-Al2O3), oxide of zirconium (ZrO2) and mixed oxide of zirconium and g-alumina had been prepared and characterized. The bi-component supports containing ( 15%) ZrO2/g-Al2O3 had been prepared by two different methods : in the first, an acid suspension of comercial oxide of zirconium was used and in the second, oxide of zirconium was precipitated from acetate. The catalysts were tested in ethanol steam reforming reaction to verify the effect of the support on the distribution of the products. For the characterization, the following techniques were used. Superficial specific area (B.E.T,), temperature programmed reduction (TPR.), X-ray powder diffraction (XRD) and spectroscopy of molecular absorption in the UV-vis, for identification of [PtOxCly]s 2- species. The ethanol conversion and product distribution were different for each support tested and for different time of contact (W/F) used. The catalyst (1%) Pt/g-Al2O3 presented the best selectivity for the hydrogen production and the lower conversion for ethanol. The catalysts with bi-component support (15%) ZrO2/ g-Al2O3 and pure ZrO2 presented high ethanol conversion and lower selectivity for hydrogen production with high selectivity and formation of bio-products.

Neste trabalho, investigou-se a atividade catalítica de materiais a base de Ni/YSZ modificados com Rh ou Ru a 0,5%, 1% e 3%, para a reforma a vapor de etanol (RVE) e seus desempenhos como eletrocatalisadores em células a combustível de óxido sólido (SOFCs - Solid Oxide Fuel Cell). Os catalisadores foram preparados pelo método Pechini e de impregnação. A caracterização estrutural foi realizada utilizando-se as técnicas de Energia Dispersiva de Raios X, Difratometria de Raios X, Redução à Temperatura Programada, Fisissorção de Nitrogênio, Microscopia Eletrônica de Varredura e Análise Elementar. Os testes catalíticos foram realizados a 700 e 900 °C, em uma linha de reação acoplada a um cromatógrafo a gás para o monitoramento dos produtos reacionais gasosos. Os produtos líquidos resultantes da RVE foram analisados por Cromatografia Líquida de Alta Eficiência (CLAE). O objetivo principal foi correlacionar a estrutura e a composição destes materiais com a produção de H2, distribuição de outros produtos reacionais e formação de depósitos de carbono. Os resultados obtidos mostraram que a incorporação de Rh ou Ru no catalisador de Ni/YSZ não resultou em mudanças significativas na estrutura e atividade catalítica, porém promoveu uma diminuição na quantidade de carbono formado, sendo mais expressiva para o caso da adição de Rh. O aumento da temperatura de reação de 700 °C para 900 °C resultou em um aumento da seletividade dos catalisadores para os produtos gasosos e diminuição da formação de coque. O estudo em uma célula unitária de SOFC foi conduzido utilizando-se platina no cátodo e 3%Rh/40%Ni/YSZ(P) no ânodo, em uma célula operando com H2 e ar a 900 °C. Embora as curvas de polarização tenham apresentado baixas densidades de potência, os resultados mostraram que o material de 3%Rh/40%Ni/YSZ(P) foi ativo para a produção e eletro-oxidação de H2 em condições reais de operação das SOFCs. Além disso, mostrou-se que é possível investigar a atividade de eletrocatalisadores de ânodos de SOFC para a reforma de etanol em linhas de reação comumente utilizadas em estudos de catálise heterogênea. / In this work, it was investigated the electrocatalytic activity of Ni/YSZ promoted with Rh or Ru (0.5 wt%, 1.0 wt% and 3.0 wt% content) for the Ethanol Steam Reforming (ESR) reaction, and their performance as electrocatalysts in Solid Oxide Fuel Cells (SOFCs). The catalysts were prepared by the Pechini and Impregnation methods. The material characterization was carried out by Energy Dispersive X-ray (EDX), X-ray Diffraction (DRX), Temperature Programmed Reduction (TPR-H2), N2 physisorption, Scanning Electron Microscopy (SEM), and Elemental Analysis. The catalytic tests were performed at 700 and 900 °C in a reaction system coupled to a gas chromatograph in order to monitor the gaseous products. The liquid products were analyzed by High Performance Liquid Chromatography (HPLC). The structure and composition of these catalysts were correlated to the H2 formation, with the distribution of other parallel reaction products, including the carbon deposition. The obtained results showed that the incorporation of Rh or Ru does not change significantly the structure and catalytic activity, but it decreases the carbon deposits, being more significant for the addition of Rh. The increase of the reaction temperature from 700 °C to 900 °C increased the gaseous products selectivities and decreased the carbon deposition. The study in SOFC unit cells were conducted using platinum and 3%Rh/40%Ni/YSZ(P) in the cathode and anode, respectively. The SOFC operated with H2 and air, and 900 °C. Although the polarization curves have presented low power densities, the obtained results showed that the 3%Rh/40%Ni/YSZ(P) electrocatalyst was active for the H2 production and eletro-oxidation in the SOFC real operation conditions. Furthermore, the results have demonstrated that it is possible to investigate SOFC electrocatalysts activity for the ethanol steam reforming in reaction lines commonly utilized in heterogeneous catalysis studies.

Vehicles powered by fuel cells are from an environmentalaspect superior to the traditional automobile using internalcombustion of gasoline. Power systems which are based upon fuelcell technology require hydrogen for operation. The ideal fuelcell vehicle would operate on pure hydrogen stored on-board.However, storing hydrogen on-board the vehicle is currently notfeasible for technical reasons. The hydrogen can be generatedon-board using a liquid hydrogen carrier such as methanol andgasoline. The objective of the work presented in this thesiswas to develop a catalytic hydrogen generator for automotiveapplications using methanol as the hydrogen carrier. The first part of this work gives an introduction to thefield of methanol reforming and the properties of a fuel cellbased power system. Paper I reviews the catalytic materials andprocesses available for producing hydrogen from methanol. The second part of this thesis consists of an experimentalinvestigation of the influence of the catalyst composition,materials and process parameters on the activity andselectivity for the production of hydrogen from methanol. InPapers II-IV the influence of the support, carrier andoperational parameters is studied. In Paper V an investigationof the catalytic properties is performed in an attempt tocorrelate material properties with performance of differentcatalysts. In the third part of the thesis an investigation isperformed to elucidate whether it is possible to utilizeoxidation of liquid methanol as a heat source for an automotivereformer. In the study which is presented in Paper VI a largeseries of catalytic materials are tested and we were able tominimize the noble metal content making the system more costefficient. In the final part of this thesis the reformer prototypedeveloped in the project is evaluated. The reformer which wasconstructed for serving a 5 kWe fuel cell had a highperformance with near 100 % methanol conversion and COconcentrations below 1 vol% in the product stream. The resultsof this part are presented in Paper VII. <b>Keywords:</b>methanol, fuel cell, vehicle, catalyst,copper, hydrogen, on-board, steam reforming, partial oxidation,combined reforming, oxidative steam reforming, auto-thermalreforming, zinc, zirconium, chromium, aluminium oxide,manganese, characterization, temperature programmed reduction,X-ray diffraction, chemisorption, carbon monoxide, poisoning,reformer.

Solid oxide fuel cells (SOFCs) conventionally operate between 800 and 1000°C. The barriers for full-scale commercialization of SOFCs are the high cost and relatively poor long-term stability due to the high temperatures used in current state-of-the-art SOFCs. One solution is to decrease the operating temperature, e.g. to 550-750°C but this requires developing new electrolytes and electrode materials. Also, to increase efficiency and practicality, the anode should be able to internally reform hydrocarbon fuels especially methane because it is the most common hydrocarbon in natural gas. The overall goal of this research is to develop a coke-tolerant Ni1-x-yCuxMgyO-SDC anode for methane fuelled IT-SOFCs. The Ni-Cu-Mg-O-SDC anode has been chosen based on the premises that doped-ceria is suitable for intermediate operating temperatures (550-800°C), Ni is known as an active metal and good electronic conductor, Cu increases resistance to coking, MgO helps prevent agglomeration of Ni during reduction, and finally SDC improves oxide ion transport to the cell at this intermediate temperature range. In this work, these materials were characterized in three primary ways: material physical and chemical properties, methane steam reforming activity and electrochemical performance. Two different methods have been used to add Cu to Ni1-yMgyO: a one-step co-precipitation method and a two-step co-precipitation/impregnation method. For the first method, Ni1-x-yCuxMgyO was synthesized via co-precipitation of Ni, Mg and Cu. In the two-step method, Ni0.9Mg0.1O was first prepared by co-precipitation, followed by addition of copper to Ni0.9Mg0.1O by impregnation. However, co-precipitation of all metal in one step limits the sintering temperature of the anode in the cell fabrication due to the low boiling point of CuO. Therefore, co-precipitation of Cu is not a practical method and only Cu impregnation should be considered for practical SOFC applications. It was found that the addition of Mg (Ni0.9Mg0.1O) lowers the reducibility of NiO. Addition of Cu to Ni0.9Mg0.1O up to 5% shows similar reducibility as Ni0.9Mg0.1O. The reducibility of Ni1-x-yCuxMgyO becomes lower when the Cu content is increased to 10%. Nonetheless, all materials are fully reduced at 750ºC. The XRD patterns of pure NiO, Ni0.9Mg0.1O, and the Cu-containing material when Cu is less than 10 mol% are similar. The lower reducibility of Ni-Mg-O and Ni-Cu-Mg-O compared to NiO indicates that they form a solid solution with NiO as the matrix. Solid oxide fuel cells (SOFCs) conventionally operate between 800 and 1000°C. The barriers for full-scale commercialization of SOFCs are the high cost and relatively poor long-term stability due to the high temperatures used in current state-of-the-art SOFCs. One solution is to decrease the operating temperature, e.g. to 550-750°C but this requires developing new electrolytes and electrode materials. Also, to increase efficiency and practicality, the anode should be able to internally reform hydrocarbon fuels especially methane because it is the most common hydrocarbon in natural gas. The overall goal of this research is to develop a coke-tolerant Ni1-x-yCuxMgyO-SDC anode for methane fuelled IT-SOFCs. The Ni-Cu-Mg-O-SDC anode has been chosen based on the premises that doped-ceria is suitable for intermediate operating temperatures (550-800°C), Ni is known as an active metal and good electronic conductor, Cu increases resistance to coking, MgO helps prevent agglomeration of Ni during reduction, and finally SDC improves oxide ion transport to the cell at this intermediate temperature range. In this work, these materials were characterized in three primary ways: material physical and chemical properties, methane steam reforming activity and electrochemical performance. Two different methods have been used to add Cu to Ni1-yMgyO: a one-step co-precipitation method and a two-step co-precipitation/impregnation method. For the first method, Ni1-x-yCuxMgyO was synthesized via co-precipitation of Ni, Mg and Cu. In the two-step method, Ni0.9Mg0.1O was first prepared by co-precipitation, followed by addition of copper to Ni0.9Mg0.1O by impregnation. However, co-precipitation of all metal in one step limits the sintering temperature of the anode in the cell fabrication due to the low boiling point of CuO. Therefore, co-precipitation of Cu is not a practical method and only Cu impregnation should be considered for practical SOFC applications. It was found that the addition of Mg (Ni0.9Mg0.1O) lowers the reducibility of NiO. Addition of Cu to Ni0.9Mg0.1O up to 5% shows similar reducibility as Ni0.9Mg0.1O. The reducibility of Ni1-x-yCuxMgyO becomes lower when the Cu content is increased to 10%. Nonetheless, all materials are fully reduced at 750ºC. The XRD patterns of pure NiO, Ni0.9Mg0.1O, and the Cu-containing material when Cu is less than 10 mol% are similar. The lower reducibility of Ni-Mg-O and Ni-Cu-Mg-O compared to NiO indicates that they form a solid solution with NiO as the matrix. Addition of Mg also lowers the BET specific surface area from 11.5 m2/g for NiO:SDC to 10.4 m2/g for Ni0.9Mg0.1O. The surface area is further reduced when Cu is added; for example, at 10% Cu, the surface area is 8.2 m2/g. The activity of 50wt% Ni1-x-yCuxMgyO/50wt% SDC samples for methane steam reforming (SMR) and water-gas-shift reaction (WGS) was evaluated in a fully automated catalytic fixed-bed reactor where the exiting gases were analyzed online by a gas chromatograph (GC). The tests were performed at steam-to-carbon ratios (S/C) of 3, 2 and 1, and at temperatures of 750°C and 650°C for twenty hours. Higher methane conversions were obtained at the higher temperature and higher S/C ratio. Higher methane conversion are obtained using NiO:SDC and Ni0.9Mg0.1O:SDC than Ni-Cu-Mg-O. The conversion decreases with increasing Cu content. Over NiO:SDC and Ni0.9Mg0.1O:SDC the methane conversions are the same; for example 85% at 750°C for S/C of 3. At the same conditions, impregnation of 5%Cu and 10%Cu yields lower conversions: 62% and 48%, respectively. The activity for the WGS reaction was determined by mornitoring CO2/(CO+CO2) ratio. As expected because WGS is a moderately exothermic reaction, this ratio decreases when increasing the temperature. However, the CO2/(CO+CO2) ratio increases with higher S/C. The results indicate that adding Mg does not affect the WGS activity of NiO. The WGS activity of Ni0.9Mg0.1O:SDC is higher when Cu is added. The effect of additional Cu is more pronounced at 650ºC. At 750°C, changing the amount of Cu does not change the WGS activity because the WGS reaction rapidly reaches equilibrium at this high temperature. At 750°C for S/C of 1, carbon filaments were found in all samples. At 650ºC, different types of deposited carbon were observed: carbon fibers and thin graphite layers. Spent NiO:SDC had the longest carbon fibers. Addition of Mg significantly reduced the formation of carbon fibers. Impregnating 5% Cu on Ni0.9Mg0.1O:SDC did not change the type of deposited carbon. Monitoring the amount of deposited carbon on Ni0.9Mg0.1O:SDC, 3%Cu and 5%Cu impregnated on Ni0.9Mg0.1O:SDC for S/C of 0 at 750ºC showed that Cu addition deactivated methane cracking causing a reduction in the amount of carbon deposited. Electrochemical performance in the presence of dry and humidified hydrogen was determined at 600, 650, 700 and 750ºC. Electrolyte-supported cells constructed with four different anodes were tested using polarization curve and electrochemical impedance spectra. The four anodes were NiO:SDC, Ni0.9Mg0.1O:SDC, 3%Cu and 5%Cu on Ni0.9Mg0.1O:SDC. Adding Mg improved the maximum power density from 356 mW.cm-2 with NiO:SDC to 369 mW.cm-2 with Ni0.9Mg0.1O:SDC at 750ºC in dry hydrogen. Addition of Cu, on the other hand, lowered the maximum power density to 325 mW.cm-2 with 3%Cu impregnated and to 303 mW.cm-2 with 5% Cu impregnated. The cell with Ni0.9Mg0.1O:SDC was also tested under dry methane. To minimize methane cracking under this extreme condition, a current density of 0.10 A.cm-2 was always drawn when methane was present in the feed. The voltage decreased during the first hour from 0.8 to 0.5 V, then remained stable for 10 hours, and then started to drop again. Many small cracks were observed on the anode after completion of the electrochemical test, but there was no evidence of much carbon being deposited. In addition to dry methane, tests were also carried out, using the same material, with a H2O/CH4 mixture of 1/6 in order to generate a polarization curve at 750°C. Under these conditions, the maximum power density was 226 mW.cm-2. This is lower than the maximum power density obtained with humidified hydrogen, which was 362 mW.cm-2.

The present work aimed at designing a thermally efficient microreactor system coupling methanol steam reforming with methanol combustion for autothermal hydrogen production. A preliminary study was performed by analyzing three prototype reactor configurations to identify the optimal radial distribution pattern upon enhancing the reactor self-insulation. The annular heat integration pattern of Architecture C showed superior performance in providing efficient heat retention to the system with a 50 - 150 degrees C decrease in maximum external-surface temperature. Detailed work was performed using Architecture C configuration to optimize the catalyst placement in the microreactor network, and optimize reforming and combustion flows, using no third coolant line. The optimized combustion and reforming catalyst configuration prevented the hot-spot migration from the reactor midpoint and enabled stable reactor operation at all process flowrates studied. Best results were obtained at high reforming flowrates (1800 sccm) with an increase in combustion flowrate (300 sccm) with the net H2 yield of 53% and thermal efficiency of >80% from methanol with minimal insulation to the heatintegrated microchannel network. The use of the third bank of channels for recuperative heat exchange by four different reactor configurations was explored to further enhance the reactor performance; the maximum overall hydrogen yield was increased to 58% by preheating the reforming stream in the outer 16 heat retention channels. An initial 3-D COMSOL model of the 25-channeled heat-exchanger microreactor was developed to predict the reactor hotspot shape, location, optimum process flowrates and substrate thermal conductivity. This study indicated that low thermal conductivity materials (e.g. ceramics, glass) provides enhanced efficiencies than high conductivity materials (e.g. silicon, stainless steel), by maintaining substantial thermal gradients in the system through minimization of axial heat conduction. Final summary of the study included the determination of system energy density; a gravimetric energy density of 169.34 Wh/kg and a volumetric energy density of 506.02 Wh/l were achieved from brass architectures for 10 hrs operation, which is higher than the energy density of Li-Ion batteries (120 Wh/kg and 350 Wh/l). Overall, this research successfully established the optimal process flowrates and reactor design to enhance the potential of a thermally-efficient heat-exchanger microchannel network for autothermal hydrogen production in portable applications.

The world&rsquo / s being alerted to the global warming danger and the depletion of fossil fuel resources, has increased the importance of the clean and renewable hydrogen energy. Bioethanol has high potential to be used as a resource of hydrogen since it is a non-petroleum feedstock and it is able to produce hydrogen rich mixture by steam reforming reactions. Discovery of mesoporous MCM-41 type high surface area silicate-structured materials with narrow pore size distributions (20-100 &Aring / ) and high surface areas (up to 1500 m2/g) opened a new avenue in catalysis research. Catalytic activity of such mesoporous materials are enhanced by the incorporation of active metals or metal oxides into their structure. Nickel and copper are among the most active metals to be used in steam reforming of ethanol to produce hydrogen. In this study, copper and nickel incorporated MCM-41 type catalytic materials were tested in the steam reforming of ethanol. Two Ni-MCM-41 samples having different Ni/Si ratios were prepared by high temperature direct synthesis method and two Cu-MCM-41 samples having same Cu/Si ratios were synthesized by two different methods namely, high temperature direct synthesis method and impregnation method. The synthesized materials characterized by XRD, EDS, SEM, N2 physisorption and TPR techniques. XRD results showed that Ni-MCM-41 and Cu-MCM-41 catalysts had typical MCM-41 structure. The d100 and lattice parameter values of Ni-HT (I) (Ni-MCM-41 sample having 0.036 Ni/Si atomic ratio) was obtained as 3.96 and 4.57 nm., respectively. In addition Ni-HT (I) was found to have a surface area of 860.5 m2/g and 2.7 nm pore diameter. The d100 and lattice parameter values for a typical Cu-MCM-41 prepared by impregnation method having Cu/Si atomic ratio of 0.19 were obtained as 3.6 and 4.2 nm., respectively. This sample also has a 631 m2/g surface area and 2.5 nm pore diameter. Steam reforming of ethanol was investigated in the vapor phase by using Ni-MCM-41 and Cu-MCM-41 catalysts between 300&deg / C and 550&deg / C. Results proved that Ni incorporated MCM-41 type catalytic materials were highly active in hydrogen production by steam reforming of ethanol and actualized almost complete ethanol conversion for Ni-MCM-41 having Ni/Si atomic ratio of 0.15 over 500&deg / C . The side products obtained during reforming are methane and formaldehyde. Although the Cu-MCM-41 samples were not as active as Ni-MCM-41, it was observed that Cu-MCM-41 catalyst synthesized by the impregnation method showed an ethanol conversion of 0.83. However, the main product was ethylene with the copper incorporated catalysts. Effects of space time, the operating conditions (reaction temperature), metal/Si ratio of the catalyst and the preparation method on the product distributions were also investigated and best reaction conditions were searched.

<p>Vehicles powered by fuel cells are from an environmentalaspect superior to the traditional automobile using internalcombustion of gasoline. Power systems which are based upon fuelcell technology require hydrogen for operation. The ideal fuelcell vehicle would operate on pure hydrogen stored on-board.However, storing hydrogen on-board the vehicle is currently notfeasible for technical reasons. The hydrogen can be generatedon-board using a liquid hydrogen carrier such as methanol andgasoline. The objective of the work presented in this thesiswas to develop a catalytic hydrogen generator for automotiveapplications using methanol as the hydrogen carrier.</p><p>The first part of this work gives an introduction to thefield of methanol reforming and the properties of a fuel cellbased power system. Paper I reviews the catalytic materials andprocesses available for producing hydrogen from methanol.</p><p>The second part of this thesis consists of an experimentalinvestigation of the influence of the catalyst composition,materials and process parameters on the activity andselectivity for the production of hydrogen from methanol. InPapers II-IV the influence of the support, carrier andoperational parameters is studied. In Paper V an investigationof the catalytic properties is performed in an attempt tocorrelate material properties with performance of differentcatalysts.</p><p>In the third part of the thesis an investigation isperformed to elucidate whether it is possible to utilizeoxidation of liquid methanol as a heat source for an automotivereformer. In the study which is presented in Paper VI a largeseries of catalytic materials are tested and we were able tominimize the noble metal content making the system more costefficient.</p><p>In the final part of this thesis the reformer prototypedeveloped in the project is evaluated. The reformer which wasconstructed for serving a 5 kWe fuel cell had a highperformance with near 100 % methanol conversion and COconcentrations below 1 vol% in the product stream. The resultsof this part are presented in Paper VII.</p><p><b>Keywords:</b>methanol, fuel cell, vehicle, catalyst,copper, hydrogen, on-board, steam reforming, partial oxidation,combined reforming, oxidative steam reforming, auto-thermalreforming, zinc, zirconium, chromium, aluminium oxide,manganese, characterization, temperature programmed reduction,X-ray diffraction, chemisorption, carbon monoxide, poisoning,reformer.</p>

Μελετήθηκε η αντίδραση αναμόρφωσης της αιθανόλης με ατμό προς παραγωγή υδρογόνου για την τροφοδοσία στοιχείων καυσίμου. Η παραγωγή υδρογόνου από αιθανόλη, αποτελεί ελκυστική διεργασία τόσο από οικονομική, όσο και από περιβαλλοντική άποψη. Το παραγόμενο υδρογόνο μπορεί να χρησιμοποιηθεί σε στοιχεία καυσίμου ως ρεύμα τροφοδοσίας, όπου οξειδώνεται ηλεκτροχημικά παρουσία αέρα αποδίδοντας ηλεκτρική ενέργεια και θερμότητα με μοναδικό προϊόν καύσης το νερό. Η αντίδραση αναμόρφωσης της αιθανόλης με ατμό είναι θερμοδυναμικά εφικτή και η αύξηση της θερμοκρασίας οδηγεί σε αυξημένη απόδοση σε υδρογόνο. Η συνολική διεργασία παραγωγής υδρογόνου από ατμοαναμόρφωση της αιθανόλης έχει υψηλότερη θεωρητική απόδοση από την ατμοαναμόρφωση του μεθανίου, η οποία είναι η κύρια διεργασία παραγωγής υδρογόνου σήμερα. Οι μελέτες της αντίδρασης αναμόρφωσης της αιθανόλης με ατμό σε καταλύτες κοβαλτίου, ευγενών μετάλλων και νικελίου, έδειξαν ότι οι βέλτιστοι καταλύτες της διεργασίας είναι οι 2% Rh/Al2O3, 5% Ru/Al2O3 και 17% Ni/(La2O3/Al2O3). Οι καταλύτες νικελίου εναποτεθειμένοι σε γ-Al2O3, La2O3 και La2O3/Al2O3 μελετήθηκαν προκειμένου να διερευνηθεί το δίκτυο των αντιδράσεων της αιθανόλης με τον ατμό με χρήση δυναμικών τεχνικών και τεχνικών μόνιμης κατάστασης. Προσεγγίστηκε το δίκτυο αντιδράσεων και τιτλοδοτήθηκε ο εναποτεθειμένος άνθρακας. Αναπτύχθηκαν κεραμικοί και μεταλλικοί θερμικά ολοκληρωμένοι αντιδραστήρες αναμόρφωσης της αιθανόλης με ατμό. Η πραγματοποίηση των αντιδράσεων αναμόρφωσης και καύσης στον κεραμικό αντιδραστήρα οδήγησε σε ικανοποιητική απόδοση. Παράλληλα, διεξήχθησαν πειράματα αναμόρφωσης και καύσης της αιθανόλης στο μεταλλικό αντιδραστήρα με χρήση καταλυτικών κλινών. Τα πειράματα αναμόρφωσης - καύσης απέδειξαν τη λειτουργικότητα του συστήματος, ενώ η σχετική θέση των καταλυτικών κλινών διαπιστώθηκε ότι αποτελεί σημαντικό παράγοντα στην απόδοση του αντιδραστήρα. Τέλος, αναπτύχθηκαν καινοτόμοι μέθοδοι εναπόθεσης καταλυτικών στρωμάτων στις επιφάνειες μεταλλικών σωλήνων. Στην εξωτερική επιφάνεια εναποτέθηκε αλούμινα ως υπόστρωμα για τον καταλύτη αναμόρφωσης με ψεκασμό πλάσματος, ενώ στο εσωτερικό του σωλήνα χρησιμοποιήθηκε μέθοδος εναπόθεσης αλουμινίου για τη δημιουργία του απαιτούμενου συγκολλητικού υποστρώματος. Οι καταλύτες που παρήχθησαν είχαν υψηλή αντοχή σε θερμικούς κύκλους και μεγάλη απόδοση στην αντίδραση αναμόρφωσης. / Production of hydrogen from steam reforming of ethanol is examined for application in fuel cells. The production of hydrogen from ethanol is an attractive operation from economical as well as from environmental point of view. The produced hydrogen can be fed to fuel cells, undergoing oxidation and producing electric energy and heat with the only combustion product being water. Steam reforming of ethanol is thermodynamically feasible and high temperatures result in high efficiency towards hydrogen production. The overall thermal efficiency of the operation is calculated and proven to be higher than the respective value of steam reforming of methane, which is the main commercial hydrogen producing operation. Steam reforming of ethanol was studied with catalysts based on Co, noble metals and Ni. The most promising materials were found to be the 2% Rh/Al2O3, 5% Ru/Al2O3 and 17% Ni/(La2O3/Al2O3) catalysts. The reaction network of steam reforming of ethanol, as well as carbon deposition, over nickel catalysts supported on γ-Αl2O3, La2O3 and La2O3/γ-Al2O3 is investigated employing transient and steady state techniques. Ceramic and metallic heat integrated reactors were developed for the reaction of steam reforming of ethanol. Experiments of coupled combustion – reformation in the ceramic reactor resulted in increased efficiency. In addition, experiments of coupled combustion – reformation were carried out in a metallic reactor by use of catalytic beds. The combustion-reformation experiments proved the effectiveness of the reactor, while the relative position of the two catalytic beds plays important role in the efficiency of the reactor. Finally, novel methods of catalyst deposition over metallic tubes were developed. On the outer surface an intermediate film of aluminum oxide was deposited by means of thermal plasma spraying in order to support the catalyst. Over the inner surface of the tube, aluminum powder was deposited and thermally processed to produce the necessary intermediate substrate. The materials produced by the above mentioned methods, were rigid and stable under extreme thermal-cycles, additionally the reforming material exhibited high efficiency.

Solid oxide fuel cells (SOFCs) conventionally operate between 800 and 1000°C. The barriers for full-scale commercialization of SOFCs are the high cost and relatively poor long-term stability due to the high temperatures used in current state-of-the-art SOFCs. One solution is to decrease the operating temperature, e.g. to 550-750°C but this requires developing new electrolytes and electrode materials. Also, to increase efficiency and practicality, the anode should be able to internally reform hydrocarbon fuels especially methane because it is the most common hydrocarbon in natural gas. The overall goal of this research is to develop a coke-tolerant Ni1-x-yCuxMgyO-SDC anode for methane fuelled IT-SOFCs. The Ni-Cu-Mg-O-SDC anode has been chosen based on the premises that doped-ceria is suitable for intermediate operating temperatures (550-800°C), Ni is known as an active metal and good electronic conductor, Cu increases resistance to coking, MgO helps prevent agglomeration of Ni during reduction, and finally SDC improves oxide ion transport to the cell at this intermediate temperature range. In this work, these materials were characterized in three primary ways: material physical and chemical properties, methane steam reforming activity and electrochemical performance. Two different methods have been used to add Cu to Ni1-yMgyO: a one-step co-precipitation method and a two-step co-precipitation/impregnation method. For the first method, Ni1-x-yCuxMgyO was synthesized via co-precipitation of Ni, Mg and Cu. In the two-step method, Ni0.9Mg0.1O was first prepared by co-precipitation, followed by addition of copper to Ni0.9Mg0.1O by impregnation. However, co-precipitation of all metal in one step limits the sintering temperature of the anode in the cell fabrication due to the low boiling point of CuO. Therefore, co-precipitation of Cu is not a practical method and only Cu impregnation should be considered for practical SOFC applications. It was found that the addition of Mg (Ni0.9Mg0.1O) lowers the reducibility of NiO. Addition of Cu to Ni0.9Mg0.1O up to 5% shows similar reducibility as Ni0.9Mg0.1O. The reducibility of Ni1-x-yCuxMgyO becomes lower when the Cu content is increased to 10%. Nonetheless, all materials are fully reduced at 750ºC. The XRD patterns of pure NiO, Ni0.9Mg0.1O, and the Cu-containing material when Cu is less than 10 mol% are similar. The lower reducibility of Ni-Mg-O and Ni-Cu-Mg-O compared to NiO indicates that they form a solid solution with NiO as the matrix. Solid oxide fuel cells (SOFCs) conventionally operate between 800 and 1000°C. The barriers for full-scale commercialization of SOFCs are the high cost and relatively poor long-term stability due to the high temperatures used in current state-of-the-art SOFCs. One solution is to decrease the operating temperature, e.g. to 550-750°C but this requires developing new electrolytes and electrode materials. Also, to increase efficiency and practicality, the anode should be able to internally reform hydrocarbon fuels especially methane because it is the most common hydrocarbon in natural gas. The overall goal of this research is to develop a coke-tolerant Ni1-x-yCuxMgyO-SDC anode for methane fuelled IT-SOFCs. The Ni-Cu-Mg-O-SDC anode has been chosen based on the premises that doped-ceria is suitable for intermediate operating temperatures (550-800°C), Ni is known as an active metal and good electronic conductor, Cu increases resistance to coking, MgO helps prevent agglomeration of Ni during reduction, and finally SDC improves oxide ion transport to the cell at this intermediate temperature range. In this work, these materials were characterized in three primary ways: material physical and chemical properties, methane steam reforming activity and electrochemical performance. Two different methods have been used to add Cu to Ni1-yMgyO: a one-step co-precipitation method and a two-step co-precipitation/impregnation method. For the first method, Ni1-x-yCuxMgyO was synthesized via co-precipitation of Ni, Mg and Cu. In the two-step method, Ni0.9Mg0.1O was first prepared by co-precipitation, followed by addition of copper to Ni0.9Mg0.1O by impregnation. However, co-precipitation of all metal in one step limits the sintering temperature of the anode in the cell fabrication due to the low boiling point of CuO. Therefore, co-precipitation of Cu is not a practical method and only Cu impregnation should be considered for practical SOFC applications. It was found that the addition of Mg (Ni0.9Mg0.1O) lowers the reducibility of NiO. Addition of Cu to Ni0.9Mg0.1O up to 5% shows similar reducibility as Ni0.9Mg0.1O. The reducibility of Ni1-x-yCuxMgyO becomes lower when the Cu content is increased to 10%. Nonetheless, all materials are fully reduced at 750ºC. The XRD patterns of pure NiO, Ni0.9Mg0.1O, and the Cu-containing material when Cu is less than 10 mol% are similar. The lower reducibility of Ni-Mg-O and Ni-Cu-Mg-O compared to NiO indicates that they form a solid solution with NiO as the matrix. Addition of Mg also lowers the BET specific surface area from 11.5 m2/g for NiO:SDC to 10.4 m2/g for Ni0.9Mg0.1O. The surface area is further reduced when Cu is added; for example, at 10% Cu, the surface area is 8.2 m2/g. The activity of 50wt% Ni1-x-yCuxMgyO/50wt% SDC samples for methane steam reforming (SMR) and water-gas-shift reaction (WGS) was evaluated in a fully automated catalytic fixed-bed reactor where the exiting gases were analyzed online by a gas chromatograph (GC). The tests were performed at steam-to-carbon ratios (S/C) of 3, 2 and 1, and at temperatures of 750°C and 650°C for twenty hours. Higher methane conversions were obtained at the higher temperature and higher S/C ratio. Higher methane conversion are obtained using NiO:SDC and Ni0.9Mg0.1O:SDC than Ni-Cu-Mg-O. The conversion decreases with increasing Cu content. Over NiO:SDC and Ni0.9Mg0.1O:SDC the methane conversions are the same; for example 85% at 750°C for S/C of 3. At the same conditions, impregnation of 5%Cu and 10%Cu yields lower conversions: 62% and 48%, respectively. The activity for the WGS reaction was determined by mornitoring CO2/(CO+CO2) ratio. As expected because WGS is a moderately exothermic reaction, this ratio decreases when increasing the temperature. However, the CO2/(CO+CO2) ratio increases with higher S/C. The results indicate that adding Mg does not affect the WGS activity of NiO. The WGS activity of Ni0.9Mg0.1O:SDC is higher when Cu is added. The effect of additional Cu is more pronounced at 650ºC. At 750°C, changing the amount of Cu does not change the WGS activity because the WGS reaction rapidly reaches equilibrium at this high temperature. At 750°C for S/C of 1, carbon filaments were found in all samples. At 650ºC, different types of deposited carbon were observed: carbon fibers and thin graphite layers. Spent NiO:SDC had the longest carbon fibers. Addition of Mg significantly reduced the formation of carbon fibers. Impregnating 5% Cu on Ni0.9Mg0.1O:SDC did not change the type of deposited carbon. Monitoring the amount of deposited carbon on Ni0.9Mg0.1O:SDC, 3%Cu and 5%Cu impregnated on Ni0.9Mg0.1O:SDC for S/C of 0 at 750ºC showed that Cu addition deactivated methane cracking causing a reduction in the amount of carbon deposited. Electrochemical performance in the presence of dry and humidified hydrogen was determined at 600, 650, 700 and 750ºC. Electrolyte-supported cells constructed with four different anodes were tested using polarization curve and electrochemical impedance spectra. The four anodes were NiO:SDC, Ni0.9Mg0.1O:SDC, 3%Cu and 5%Cu on Ni0.9Mg0.1O:SDC. Adding Mg improved the maximum power density from 356 mW.cm-2 with NiO:SDC to 369 mW.cm-2 with Ni0.9Mg0.1O:SDC at 750ºC in dry hydrogen. Addition of Cu, on the other hand, lowered the maximum power density to 325 mW.cm-2 with 3%Cu impregnated and to 303 mW.cm-2 with 5% Cu impregnated. The cell with Ni0.9Mg0.1O:SDC was also tested under dry methane. To minimize methane cracking under this extreme condition, a current density of 0.10 A.cm-2 was always drawn when methane was present in the feed. The voltage decreased during the first hour from 0.8 to 0.5 V, then remained stable for 10 hours, and then started to drop again. Many small cracks were observed on the anode after completion of the electrochemical test, but there was no evidence of much carbon being deposited. In addition to dry methane, tests were also carried out, using the same material, with a H2O/CH4 mixture of 1/6 in order to generate a polarization curve at 750°C. Under these conditions, the maximum power density was 226 mW.cm-2. This is lower than the maximum power density obtained with humidified hydrogen, which was 362 mW.cm-2.

Depletion in the reserves of fossil fuels, inefficient energy production from these fuels and the negative effect of their usage on atmosphere, and thereby, on human health have accelerated researches on clean energy. Hydrogen produced from ethanol when used in fuel cells not only generates efficient energy but also creates a closed carbon cycle in nature. ZnO and Cu/ZnO catalysts are known with their superior performance in alcohol synthesis. From the principle of microkinetic reversibility they are expected to be superior catalysts for the steam reforming reaction of ethanol as well. ZnO catalysts can be modified by precious, Pd, or non-precious, Cu, metals to enhance hydrogen desorption capability, and dispersed on SiO2 for high surface areas via sol-gel technique. Steam reforming tests over ZnO catalysts revealed that they act only as ethanol dehydrogenation catalysts in the temperature range of 300-500C. Promotion with Pd or Cu decreased hydrogen selectivity due most probably to unreachable closed pores of the catalysts. Autothermal reforming tests over both ZnO/SiO2 and Co/SBA-15 catalysts, on the other hand, gave rise to the formation of several side products.