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.

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.

The applications of polyaniline (PAni) for use as electrolyte in Polymer-Electrolyte-Membrane Fuel Cells (PEMFC) were investigated. P Ani was dissolved in N-methyl pyrrolidone (NMP), cast as Emeraldine Base membranes (EB) and then doped with halide acids. The proton conductivity was measured according to Hittorf. The chloride ion distribution within the membrane was evaluated using energy-dispersive-X-ray analysis (EDX) and photometric analysers and the diffusion coefficient was calculated. The specific resistance was determined using conventional 4-point measurement. Halide doped membranes were found to be proton conducting, however, during cell operation halide removal occurred causing a rapid decline in the cell performance. The maximum power density achieved was O.3m W·cm-2 for a 70J.1m thick membrane saturate with chloride between 3,5 and 4,5mgchloride per gPAni. Composite membranes with phosphotungstic acid (PWA), antimonic acid (AA) and zirconium phosphate (ZP) were developed and also tested in a standard measuring fuel cell. While membranes produced via ion exchange (ZP) showed the same result like halide doped ones, AA composite membranes showed a stable voltage and current results. The highest measured outcome of 373.3mW·cm-2 was found with a PWA membrane, produced through dispersing 3g of phosphotungstic acid in 300ml of a 1% polyanilinelNMP solution. It was also observed, that the higher power density was obtained from the fuel cell which uses the lower-loaded membrane. It is clear that a positive effect on the cell performance is given by the addition of phosphotungstic acid to the polyaniline membrane. Therefore, the saturation of PW A have to be taken into account to not lower the power density.

Ce projet de thèse a concerné la recherche et le développement de catalyseurs multifonctionnels efficaces et de procédés catalytiques en une étape (hydrolyse-déshydratation, hydrolyse-oxydation) pour la transformation de la cellulose en produits chimiques à valeur ajoutée (glucose, 5-HMF, acide formique). Ces produits sont également connus sous le nom de molécules plateformes et ils présentent un intérêt dans une large gamme d'applications, par exemple, pour les industries alimentaires et chimiques et pour la production de carburants. Dans ce projet, des recherches systématiques sur la synthèse de l'acide formique en présence de catalyseurs HPA contenant du vanadium ont d'abord été conduites. En particulier, l'influence de la composition du catalyseur et des paramètres du procédé sur le rendement en produit cible a été étudiée. Le rendement en AF obtenu (66%) est supérieur à tous les résultats rapportés dans la littérature à ce jour. Les catalyseurs NbOx / ZrO2 ont été évalués pour la première fois sur la réaction d'hydrolyse-déshydratation de la cellulose microcristalline activée en milieu aqueux. Des rendements élevés en glucose et en 5-HMF (22 et 16%, respectivement) ont été observés. Des catalyseurs carbonés à base du matériau Sibunit modifié ont été utilisés pour la première fois pour l'hydrolyse-déshydratation de la cellulose. Les rendements en glucose (jusqu'à 74% dans un réacteur en continu) et en 5-HMF (jusqu'à 21% dans un réacteur statique) ont été obtenus en présence de Sibunit modifié par sulfonation et / ou oxydation. Ces résultats sont également supérieurs à ceux reportés à ce jour sur les systèmes catalytiques carbonés. La relation entre l'activité sur les réactions d’hydrolyse-déshydratation et la méthode d'activation du carbone a été étudiée en profondeur. L'étude du mécanisme et de la cinétique de la réaction d'hydrolyse-déshydratation de la cellulose en présence de catalyseurs acides solides a également été réalisée. / The PhD project was devoted to search for and to develop effective multifunctional catalysts and catalytic one-stage processes (hydrolysis-dehydration, hydrolysis-oxidation) for transformation of cellulose to valuable chemicals (glucose, 5-HMF, formic acid). These products are also known as platform molecules and they seem to be promising for a wide range of application in food and chemical industries and for fuel production. In this project, systematic investigations of the formic acid synthesis in the presence of vanadium-containing HPA catalysts was first conducted; the influence of the catalyst composition and process parameters on the yield of the target product was studied. The obtained FA yield (66 %) was superior to all the results reported in literature. The NbOx/ZrO2 catalysts were applied for the first time for hydrolysis-dehydration of activated microcrystalline cellulose in pure water. High yields of glucose and 5-HMF (22 and 16 %, respectively) were observed. Carbon catalysts based on modified Sibunit material was used for the first time for cellulose hydrolysis-dehydration. The yields of glucose (up to 74 % in a flow reactor) and 5-HMF (up to 21 % in a static reactor) were obtained in the presence of Sibunit modified by sulfation and/or oxidation; these are much superior to the results on carbon catalytic systems reported in literature. The relation between the activity to hydrolysis-dehydration and the method of the carbon activation was thoroughly studied. Investigations of the mechanism and kinetics of cellulose hydrolysis-dehydration in the presence of solid acid catalysts were also carried out.