Vehicles powered by proton exchange membrane (PEM) fuelcells are approaching commercialisation. Being inherently cleanand efficient sources of power, fuel cells constitute asustainable alternative to internal combustion engines to meetfuture low-emission legislation. The PEM fuel cell may befuelled directly by hydrogen, but other alternatives appearmore attractive at present, due to problems related to theproduction, transportation and handling of hydrogen. Fuelling with an alcohol fuel, such as methanol, which isoxidised directly at the anode, offers certain advantages.However, the efficiency of the direct-methanol fuel cell (DMFC)is still significantly lower than that of the conventionalhydrogen-fuelled PEM fuel cell, due to some technical problemsremaining unsolved. Hence, indirect fuelling by a reformedliquid fuel may be the most feasible option in the early stagesof the introduction of fuel cell vehicles. The work presented in this thesis concerns the developmentof catalysts for production of hydrogen from methanol bypartial oxidation, steam reforming or a combination thereof.The work contributes to the understanding of how thepreparation route affects catalyst morphology and howphysicochemical properties determine catalytic behaviour andreaction pathways. The thesis is a summary of seven papers published inscientific periodicals. The first paper (Paper I) reviews thecurrent status of catalytic hydrogen generation from methanol,focusing on the fuel cell application. Paper II investigatesthe partial oxidation of methanol over Cu/ZnO catalystsprepared in microemulsion and by a conventionalco-precipitation technique. The activity for methanolconversion in the low-temperature regime is found to besignificantly higher over the former materials and the workcontinues by determining the nature of possible Cu-ZnOinteractions in the catalysts by studying their physicochemicalproperties more thoroughly (Paper III). In Paper IV, thepathways for methanol conversion via both partial oxidation andsteam reforming are elucidated. In Paper V, partial oxidation of methanol is studied overPd/ZnO catalysts prepared by microemulsion technique and againcompared to conventional materials. This investigationdemonstrates that although possessing high methanol conversionactivity, palladium-based catalysts are not suitable forreforming in fuel cell applications due to the considerableamounts of carbon monoxide formed. In Paper VI, methanol reforming is investigated over acommercial Cu/ZnO/Al2O3 catalyst. The mechanisms for carbonmonoxide formation and strategies for its suppression arediscussed, as well as reactor design aspects. The study alsoincludes some simple kinetic modelling. Finally, Paper VIIdescribes the optimisation of catalyst composition and processconditions to reach high hydrogen production efficiency at lowoperating temperatures and with minimum carbon monoxideformation. <b>Keywords:</b>PEM fuel cells, hydrogen, methanol, reforming,(partial) oxidation, reaction pathways, carbon monoxide,catalyst, microemulsion, Cu/ZnO, Pd/ZnO, copper, redoxproperties, oxidation state

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.

In this research the effects of the fabrication processes of MEA on the output power of a DMFC stack are studied by changing hot-pressing conditions including pressure, temperature and time. Additionally, the effects of the various treatments of the MEAs on the output voltage and power are also studied after the hot-pressing process of MEA is finished. In the first experimental study the catalyst of cathode is 4.0mg/cm unsupported HP Pt black, Anode is 4.0mg/cm 80% HP Pt-Ru Alloy (1: 1), membrane is Nafion 117, and bipolar plates is heterogeneous carbon fiber bipolar plate developed by our fuel cell laboratory. The MEA for single cell includes the area of membrane 3*3 cm2 the active area of electrode 1.5*1.5 cm2. Under the hot-pressing conditions 120 oC, 100 bar and 90s, the maximum power density can reach a value of 18 mW/cm2 at the conditions of methanol concentration 3 M, air-breathing, and room temperature After several experiments, we observed that performances of MEAs decayed with time. So we designed a series of experiments to inspect the various possible reasons and try to solve this problem. The cylindrical DMFC is one of the most important developments in our lab. However, the MEAs made for plate-type DMFC do not fit the cylindrical DMFC stack properly. The electrodes easily pealed off from the membrane and the contact resistance increases after certain periods. So the hot-pressing device had been redesigned to fit the cylindrical DMFC stack. After that the total power of the 6-cell stack with total active area 15 cm2 can reach a value 135 mW. If the performance of each cell of the 6-cell stack is uniform, we expect that the total power of this stack can reach a higher value 195 mW, which can be applied to some portable electronic products.

The need for alternative transportation fuels is rising with the rapid depletion of oil reserves and the simultaneous growth of the world&amp / #8217 / s population. Production of dimethyl ether, a non-petroleum derived attractive fuel-alternate for the future, is a challenging research area. Different routes and various solid-acid catalysts are being developed in order to achieve the most efficient way of synthesizing this potential diesel alternative fuel. The focus of heterogeneous catalysis is to convert renewable feed stocks to valuable chemicals. Nafion resin and heteropolyacid compounds are active acidic catalysts with significantly low surface areas, which act as a strong barrier limiting their catalytic activity. Synthesizing solid-acid catalysts by incorporation of nonporous active compounds into mesoporous silicate structured materials opens a door to producing valuable chemicals by heterogeneous catalysis. The objective of this work was to synthesize and characterize nafion and heteropolyacid incorporated nanocomposite catalysts and to catalyze DME synthesis by dehydration of methanol at different temperatures. The interactions of methanol and DME with these catalysts were also investigated by in situ FT-IR. Silicotungstic acid (STA)/Silica and Tungstophosphoric acid (TPA)/Silica catalysts were synthesized by following a one-pot hydrothermal route. These mesoporous catalysts had surface area values of 143-252 m2/g. The STA/SiO2 nanocomposite catalyst having a W/Si atomic ratio of 0.33 showed the highest activity, with a DME selectivity approaching to 100% and a methanol conversion of 60% at 250&deg / C at a space time of 0.27 s.g.cm-3. Effects of W/Si atomic ratio and the synthesis procedure on the performance of these novel materials were investigated. Nanocomposite Nafion/SiO2 solid-acid catalysts having high surface area values (595-792 m2/g) and narrow pore size distributions (4.3 nm) were successfully synthesized by a one-pot hydrothermal procedure. Effects of the modifications in the synthesis procedure concerning the surfactant removal, nafion loading, etc. were investigated based on the characterization results and activity tests. Nafion was observed to be uniformly distributed within these mesoporous catalysts. Nafion resin was also impregnated into aluminosilicate and &amp / #945 / -alumina, but one-pot synthesis was concluded to be better for obtaining well dispersed, nafion incorporated active catalysts. The Nafion/Silica catalyst synthesized by a nafion/silica weight ratio of 0.15 and washed with 2M sulfuric acid-ethanol solution exhibited the highest activity due to its highest Br&ouml / nsted, as well as Lewis acidity. A methanol conversion of 40% at 300&deg / C, 0.27 s.g.cm-3 and DME selectivity values approaching to 100% over 180&deg / C were very promising for the synthesis of this green fuel alternate over the new catalysts synthesized.

In 21st century, researchers make great effort of finding a clean transportation fuel to diminish the severe effects of conventional transportation fuel combustion such as global warming and air pollution. Dimethyl ether is considered as a strong fuel alternative due to its good burning characteristics and environmentally friendly properties. In order to produce dimethyl ether, different synthesis routes and solid acid catalysts are being utilized. SAPO-34 is an aluminophosphate based catalyst having moderate acidity. This property makes it a good candidate for the synthesis of dimethyl ether. However, SAPO-34 has microporous structure causing diffusion limitations. The objective of this study is to synthesize, characterize mesoporous SAPO-34 like catalytic materials and test the activity of them in methanol dehydration reaction. The benefit of obtaining mesoporous structure is that the diffusion limitations can be eliminated. Mesoporous SAPO-34 like catalysts were synthesized through hydrothermal synthesis route. BET surface areas of these catalysts were 117-133 m2/g. All methanol dehydration reactions were carried out at a space time of 0.14 s.g/cm3. By using mesoporous SAPO-34 like catalysts, the highest methanol conversion was 48% obtained at 550&deg / C with DME selectivity and yield values of 1 and 0.49, respectively. Since utilizing microporous SAPO-34 catalyst gave higher methanol conversion, 67%, at lower temperature, 250&deg / C, with dimethyl ether selectivity of around 1, mesoporous SAPO-34 like catalysts are not suitable for this reaction.

Due to high consumption rates of petroleum derived fuels and environmental regulations, significant search has been initiated for the development of environmental friendly and efficient fuels, which were derived from more abundant feedstocks. Dimethyl ether (DME), as having a good combustion quality and high cetane number, is an efficient alternative for diesel fuel. With improved combustion quality, the emissions from DME used engines are greatly decreased. DME synthesis can be carried out via two different methods / methanol dehydration on acidic catalysis and syn-gas conversion on bifunctional catalysis. In this study, the aim is to synthesize acidic catalysts using direct hydrothermal synthesis method for DME synthesis as using methanol as feed stock via dehydration and to characterize these materials. The support of the synthesized materials comprises of MCM-41 structure and silicotungstic acid (STA) and metals (Zr / Ni / Cu) were incorporated into the MCM-41 structure during synthesis. Two different techniques were used to extract the surfactant (CTMABr) from catalyst matrix. First one is the conventional calcination technique (at 350&deg / C) and the second is supercritical fluid extraction (at various operating conditions) with methanol modified CO2. The effect of metal loading on extraction performance is analyzed through characterizations of Ni and Cu incorporated materials. In addition, The effect of operation parameters on catalyst properties are also investigated with performing extraction at different pressures for different durations. By changing the type of metal incorporated into the catalyst, the extraction performance is also monitored. The characterization results indicated that, SFE process is also a promising method for surfactant removal. The activities of zirconium added catalysts are tested in methanol dehydration reaction towards DME. It is concluded that the conversion of methanol and selectivity of DME in presence of extracted samples are lower (maximum yield -0.54- obtained at 450&deg / C with sceSZ1) compared to the calcined materials (maximum yield -0.80- obtained at 300&deg / C with cSZ6). This result can also be foreseen by DRIFTS analysis of pyridine adsorbed samples. The acid sites of extracted materials are not as strong as in the calcined catalysts.

Membrane electrode assembly (MEA) is the foundation of the single cell as well as the core of the fuel cell when generating electricity. Its work efficiency is the key factor for single cell performance. This study aims to understand the variation between the conventional method and the decal method during the MEA process. By observing the microstructure morphology of electrode and the performance of single cell, as well as analyzing internal resistance and its stabilization, the advantages and disadvantages of MEA in the two methods is analyzed. The decal condition is 135¢XC, 15 kg/cm , 2.5 min at a high temperature (50¢XC 3M methanol), in air-breathing under atmosphere system. The maximum power density is approximately 22.5 mW/cm which is very close to the result of conventional method. The decal method is better than the conventional method particularly in regards to the high current density performance. It shows that there is an efficient influence of the decal method on the methanol mass transfer and it also improves its polarization and enlarges the current. If the single cell is operated in the high temperature, the fuel mass transfer can be advanced in the decal method and its performance can be raised. However, in the manufacturing process, more time has to be spent when producing the MEA. This experiment can be used as a reference on the single cell operation environment and manufacturing time for future studies.

The goal of this dissertation was to create a new class of DMFC targeted at high energy density and low loss for small electronic devices. In order for the DMFC to efficiently use all its fuel, with a minimum of balance of plant, a low-loss proton exchange membrane was required. Moderate conductivity and ultra low methanol permeability were needed. Fuel loss is the dominant loss mechanism for low power systems. By replacing the polymer membrane with an inorganic glass membrane, the methanol permeability was reduced, leading to low fuel loss. In order to achieve steady state performance, a compliant, chemically stable electrode structure was investigated. An anode electrode structure to minimize the fuel loss was studied, so as to further increase the fuel cell efficiency. Inorganic proton conducting membranes and electrodes have been made through a sol-gel process. To achieve higher voltage and power, multiple fuel cells can be connected in series in a stack. For the limited volume allowed for the small electronic devices, a noble, compact DMFC stack was designed. Using an ADMFC with a traditional DMFC including PEM, twice higher voltage was achieved by sharing one methanol fuel tank. Since the current ADMFC technology is not as mature as the traditional DMFCs with PEM, the improvement was accomplished to achieve higher performance from ADMFC. The ultimate goal of this study was to develop a DMFC system with high energy density, high energy efficiency, longer-life and lower-cost for low power systems.

<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>

<p>Vehicles powered by proton exchange membrane (PEM) fuelcells are approaching commercialisation. Being inherently cleanand efficient sources of power, fuel cells constitute asustainable alternative to internal combustion engines to meetfuture low-emission legislation. The PEM fuel cell may befuelled directly by hydrogen, but other alternatives appearmore attractive at present, due to problems related to theproduction, transportation and handling of hydrogen.</p><p>Fuelling with an alcohol fuel, such as methanol, which isoxidised directly at the anode, offers certain advantages.However, the efficiency of the direct-methanol fuel cell (DMFC)is still significantly lower than that of the conventionalhydrogen-fuelled PEM fuel cell, due to some technical problemsremaining unsolved. Hence, indirect fuelling by a reformedliquid fuel may be the most feasible option in the early stagesof the introduction of fuel cell vehicles.</p><p>The work presented in this thesis concerns the developmentof catalysts for production of hydrogen from methanol bypartial oxidation, steam reforming or a combination thereof.The work contributes to the understanding of how thepreparation route affects catalyst morphology and howphysicochemical properties determine catalytic behaviour andreaction pathways.</p><p>The thesis is a summary of seven papers published inscientific periodicals. The first paper (Paper I) reviews thecurrent status of catalytic hydrogen generation from methanol,focusing on the fuel cell application. Paper II investigatesthe partial oxidation of methanol over Cu/ZnO catalystsprepared in microemulsion and by a conventionalco-precipitation technique. The activity for methanolconversion in the low-temperature regime is found to besignificantly higher over the former materials and the workcontinues by determining the nature of possible Cu-ZnOinteractions in the catalysts by studying their physicochemicalproperties more thoroughly (Paper III). In Paper IV, thepathways for methanol conversion via both partial oxidation andsteam reforming are elucidated.</p><p>In Paper V, partial oxidation of methanol is studied overPd/ZnO catalysts prepared by microemulsion technique and againcompared to conventional materials. This investigationdemonstrates that although possessing high methanol conversionactivity, palladium-based catalysts are not suitable forreforming in fuel cell applications due to the considerableamounts of carbon monoxide formed.</p><p>In Paper VI, methanol reforming is investigated over acommercial Cu/ZnO/Al2O3 catalyst. The mechanisms for carbonmonoxide formation and strategies for its suppression arediscussed, as well as reactor design aspects. The study alsoincludes some simple kinetic modelling. Finally, Paper VIIdescribes the optimisation of catalyst composition and processconditions to reach high hydrogen production efficiency at lowoperating temperatures and with minimum carbon monoxideformation.</p><p><b>Keywords:</b>PEM fuel cells, hydrogen, methanol, reforming,(partial) oxidation, reaction pathways, carbon monoxide,catalyst, microemulsion, Cu/ZnO, Pd/ZnO, copper, redoxproperties, oxidation state</p>