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The ayelodehydrogenation of 7-(1-naphthyl)benz [a] anthracene to dibenzo [a,e] perylene was accomplished in 38% yield using an aluminum chloride - stannic chloride catalyst. Attempts to reproduce or to improve this yield were not successful and thereafter the only product isolated was a low melting light orange solid which was postulated to be a hydrogenated intermediate. That the orange material could be converted to dibenzo [a,e] perylene upon treatment with palladiem on charcoal in p-eymene substantiated this postulation. / Master of Science

<p>The increase in shale gas exploitation has motivated the studies towards new processes for converting light alkanes into higher valuable chemicals, including fuels. The works in this dissertation focuses on two processes: propane dehydrogenation and ethylene oligomerization. The former involves the conversion of propane into propylene and hydrogen, while the latter converts light alkenes into higher molecular weight products, such as butylene and hexene. </p> <p>The thesis project focuses on understanding the effect of geometric effects of Pt alloy catalysts for propane dehydrogenation and the methodologies for their characterization. Pt-Co bimetallic catalysts were synthesized with increasing Co loadings, characterized and evaluated for its propane dehydrogenation performance. In-situ synchrotron X-Ray Powder Diffraction (XRD) and X-Ray Absorption (XAS) were used to identify and differentiate between the intermetallic compound phases in the nanoparticle surface and core. Difference spectra between oxidized and reduced catalysts suggested that, despite the increase in Co loading, the catalytic surface remained the same, Pt₃Co in a Au₃Cu structure, while the core became richer in Co, changing from a monometallic Pt fcc core at the lowest Co loading to a PtCo phase in a AuCu structure at the highest loading. Co^II single sites were also observed on the surface, due to non-reduced Co species. The catalytic performance towards propane dehydrogenation reinforced this structure, as propylene selectivity was around 96% for all catalysts, albeit the difference in composition. The Turnover Rate (TOR) of these catalysts was also similar to that of monometallic Pt catalysts, around 0.9 s^-1, suggesting Pt was the active site, while Co atoms behaved as non-active, despite both atoms being active in their monometallic counterparts.</p> <p>In the second project, a single site Co^II catalyst supported on SiO₂ was evaluated for ethylene oligomerization activity. The catalyst was synthesized, evaluated for propane dehydrogenation, propylene hydrogenation and ethylene oligomerization activities and characterized <i>in-situ</i> by XAS and EXAFS and H₂/D₂ exchange experiments. The catalysts have shown negligible conversion at 250^oC for ethylene oligomerization, while a benchmark Ni/SiO₂ catalyst had about 20% conversion and TOR of 2.3x10^-1 s^-1. However, as the temperature increased to above 300^oC, ethylene conversion increased significantly, reaching about 98% above 425^oC. <i>In-situ</i> XANES and EXAFS characterization suggested that H₂ uptake under pure H₂ increased in about two-fold from 200^oC to 500^oC, due to the loss of coordination of Co-O bonds and formation of Co-H bonds. This was further confirmed by H₂/D₂ experiments with a two-fold increase in HD formation per mole of Co. <i>In-situ</i> XAS characterization was also performed with pure C­₂H₄ at 200^oC showed a similar trend in Co-O bond loss, suggesting the formation of Co-alkyl, similarly to that of Co-H. The <i>in-situ</i> XANES spectra showed that the oxidation state remained stable as a Co²⁺ despite the change in the coordination environment, suggesting that the reactions occurs through a non-redox mechanism. These combined results allowed the proposition of a reaction pathway for dehydrogenation and oligomerization reactions, which undergo a similar reaction intermediate, a Metal-alkyl or Metal-Hydride intermediates, activating C-H bonds at high temperatures.</p>

Thesis (MScIng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Both porous and dense hydrogen selective membranes have recently been an active area of research. The combination of a reactor and a separator in the form of a membrane reactor is seen as a feasible application in which to perform dehydrogenation reactions. These reactions are equilibrium limited so that the removal of the product H2 by a selective membrane can improve the process effectiveness. Early Pd-based membranes were made of thin-walled tubes. In an attempt to increase permeation rates, thin supported Pd membranes have been developed. This study investigated the development and performance of a catalytic membrane reactor. The membrane reactor consists of a tubular alumina membrane support coated on the inside with a film of palladium or a palladium-copper alloy. This reactor was used for the dehydrogenation of isopropanol. The thin film was coated on the alumina support using an electroless plating process. This process occurs in a liquid medium where palladium and copper are deposited by electrolysis or electroless means. With these methods alloys can also be deposited on the support. By plating a thin film of palladium on the alumina membranes, will attract hydrogen molecules from the reaction product, which will increase the reaction rate. The electroless plating process consists of four major components: (i) (ii) (iii) (iv) reducing agent ( 0.04 M hydrazine), temperature bath, stabilised source of metal ions, and support membrane (α-alumina). Heat treatment was carried out on the coated membranes for 5 hours in a hydrogen atmosphere at 450°C. The plated membranes supplied by Atech were characterised using X-ray diffraction (XRD), scanning electron microscopy (SEM) and particle induced Xray emission (PIXE) before and after heat treatment. SEM photographs showed that the pore size of the membranes was doubtful and due to that the films were not of a dense nature. XRD results revealed that heat treatment led to the formation of smaller Pd and Cu crystallites. The concentration profiles constructed from the PIXE results indicated that Cu and Pd penetrated deep into the pores of the membrane during film preparation. Different catalysts (Al2O3, MgO and SiO2) were tested and the best one was chosen as catalyst in the membrane reactor. These catalytic runs were done in a plug flow (fixedbed) reactor. Different particle sizes of catalysts were also tested. A 9.2 Cu wt % on silica achieved the highest acetone yields for the temperatures tested. Two different types of alumina membrane reactors were used. These were supplied from SCT. One membrane only coated with palladium and the other coated with palladium and copper. Selectivity and permeability tests were also carried out on these membranes. Selectivities of up to 90.6 could be reached with the palladium coated membrane. The palladium-copper plated membrane only achieved selectivities of up to 13. With heat treatment this value decreased even more. The palladium coated membrane also achieved much better conversion to acetone in the dehydrogenation of 2-propanol. The reason for that is its better selectivity. The palladium-copper membrane reactor did not show much better results than the fixed-bed reactor. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek die ontwikkeling en werk verrigting van ‘n katalitiese membraan reaktor. Die membraan reaktor bestaan uit ‘n dun film palladium of palladium-koper allooi wat aan die binnekant van ‘n silindriese alumina membraan geplateer word. Die alumina dien as membraanbasis. Hierdie reaktor sal gebruik word vir die dehidrogenering van isopropanol. Die dun films van metaal word neergeslaan op die alumina basis deur ‘n elektrodelose platerings proses. Hierdie proses vind plaas in ‘n vloeistof medium waar palladium en koper neerslag plaasvind op ‘n elektrodelose wyse. Met hierdie metode kan metaal allooie geplateer word op basis membrane. Deur ‘n dun palladium lagie aan die binnekant van die alumina membrane te plateer sal veroorsaak dat waterstof molekules uit die reaksie volume sal weg beweeg. Dit sal ‘n verhoging in reaksie tempo meebring. Die platerings proses bestaan uit vier komponente: (i) reduseermiddel (0.04M Hidrasien), (ii) temperatuur water bad, (iii) stabiliseerde bron van metaal ione (Pd/Cu kompleks oplossing), en (iv) basis membraan (α-alumina). Hittebehandeling vir 5 uur is uitgevoer op hierdie geplateerde membrane by 450°C in ‘n waterstofatmosfeer. Die geplateerde membrane is daarna gekarakteriseer- voor en na hittebehandeling. Dit is gekarakteriseer deur X-straal diffraksie (XRD), skanderings elektron mikroskopie (SEM) en partikel geïnduseerde X-straal emissie (PIXE). XRD eksperimente het gewys dat die koper en die palladium ‘n allooi gevorm het. Veranderinge in kristaltekstuur het voorgekom na hittebehandeling. Tydens hittebehandeling was kleiner palladium en koper kristalle gevorm. SEM resultate het getoon dat die film nie baie dig was nie en die porie grootte van die membrane was ook nie korrek nie. PIXE resultate het die konsentrasieprofiele van beide koper en palladium oor die dikte van die membraan bepaal. Dit het gewys dat die Cu en Pd diep binne die membraan penetreer het tydens voorbereiding van die membraan. Verskillende soorte kataliste (Al2O3, MgO and SiO2) is ondersoek vir die dehidrogenering van isopropanol. Hierdie katalitiese ondersoek is gedoen in ‘n propvloei reaktor. Die beste katalis is gekies om in die membraan reaktor te gebruik. Verskillende partikel groottes is ook ondersoek. ‘n 9.2 Cu massa % koper op silika katalis het die beste omsetting na asetoon verkry vir die temperature waarvoor toetse gedoen is. Twee tipes membraan reaktors is gebruik. Een met net ‘n palladium film, terwyl ‘n palladium-koper allooi op die ander membraan reaktor gedeponeer was. Selektiwiteits- en deurlaatbaarheids toetse is op altwee membrane gedoen. Selektiwiteite van 90.6% kon verkry word met die palladium membraan. Die palladium-koper membraan kon slegs ‘n selektiwiteit van 13% bereik. Met hittebehandeling daarvan het die selektiwiteit selfs meer afgeneem. Die palladium membraan het ook hoër omsettings na asetoon getoon. Die rede hiervoor is die membraan se hoë selektiwiteit. Die palladium-koper membraan het nie veel beter resultate as die propvloei reaktor gelewer nie.

Non-oxidative dehydrogenation of hydrocarbons is an attractive alternative route for the production of CO- and CO2-free hydrogen. It will satisfy a major requirement for successful utilization of polymer electrolyte membrane (PEM) fuel cells (< 10 ppm CO) and sequestering carbon as a potentially valuable by-product, carbon nanotubes (CNTs). Due to the deposition of carbon on the surface of catalyst particles during the reaction, catalyst performance, life-time, and purification of the generated carbon product, are significant issues to solve in order to make the process practically feasible. The scope of this thesis includes: the development of novel Fe, Ni, and Fe-Ni catalysts supported on a Mg(Al)O support to achieve improved catalytic performance with easily-purified CNTs; evaluation of catalysts for ethane/methane dehydrogenation at moderate reaction temperatures; and study of activation and deactivation mechanisms by a variety of characterization techniques including TEM, HRTEM, XRD, Mössbauer spectroscopy, and x-ray absorption fine structure (XAFS) spectroscopy. The Mg(Al)O support was prepared by calcination of synthetic MgAl-hydrotalcite with a Mg to Al ratio of 5. The catalysts were prepared either by conventional incipient wetness method or by a novel nanoparticle impregnation method, where the monodisperse catalyst nanoparticles were prepared in advance by thermal decomposition of a metal-organic complex in an organic-phase solution and then dispersed onto the Mg(Al)O support. Dehydrogenation of undiluted methane was conducted in a fix-bed plug-flow reactor. Before reaction, the catalysts were activated by reduction in hydrogen. Fe-based catalysts exhibit a higher hydrogen yield at temperature above 600ºC compared with monometallic Ni catalyst. FeNi-9 nm/Mg(Al)O, Fe-10 nm/Mg(Al)O and Fe-5 nm/ Mg(Al)O nanoparticle catalysts show much improved performance and longer life-times compared with the corresponding FeNi IW/Mg(Al)O and Fe IW/Mg(Al)O catalysts prepared by incipient wetness. 10 nm is the optimum particle size for methane dehydrogenation. Addition of Ni to Fe forming a bimetallic FeNi alloy catalyst enhances the catalytic performance at the temperatures below 650ºC. Metallic Fe, Ni, FeNi alloy and Fe-Ni-C alloy, unstable iron carbide are all catalytically active components. Catalysts deactivation is due to the carbon encapsulation. The carbon products are in the form of stack-cone CNTs (SCNTs) and multi-walled CNTs (MWNTs), depending on the reaction temperature and catalyst composition. The growth of CNTs follows a tip growth mechanism and the purity of cleaned CNTs is more than 99.5%.

A series of cationic Rh(I) diphosphine and phosphine-alkene complexes have been isolated and fully characterised. The reactivity of these species towards hydrogenation, dehydrogenation and dehydrocoupling reactions has been investigated. The use of potentially hemilabile ligands DPEphos and XANTphos in the intramolecular dehydrogenation chemistry of tricyclopentylphosphine is reported. The comparison in reactivity of these isolated diphosphine phosphine-alkene complexes towards hydrogenation and with acetonitrile is discussed along with their ability to dehydrocouple secondary silane, Ph₂SiH₂, and amine-borane H₃B·NMe₂H. The acceptorless dehydrogenation of a tethered cyclopentane with cationic Rh(I) diphosphine complexes has also been extended to include thioethers. Isolated cationic Rh(I) phosphine-alkene complexes with labile fluorobenzene ligands are found to act as a source of the reactive 12-electron [Rh{PR₂(ƞ²-C₅H₇)}]+ (R = cyclopentyl (Cyp)/ iPr) fragment in solution and can coordinate two amine-borane ligands (either H₃B·NMe₃, H₃B·NMe₂H or H₃B·NMeH₂) in a novel and unique bis-σ-binding mode. The catalytic activity of some of these isolated complexes in the dehydrocoupling of H₃B·NMe₂H and H₃B·NMeH₂ has been determined. With a view to further understanding the mechanism of catalytic transition metal assisted amine-borane dehydrogenation and dehydrocoupling, known B-N intermediates H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ were also coordinated to the [Rh{PCyp₂(ƞ²-C₅H₇)}]+ fragment and investigated with regard to their role in the catalytic cycle. Structure activity relationships determined from stoichiometric reactions of cationic Rh(I) diphosphine fluorobenzene complexes with amine-boranes enabled the design of a highly efficient homogeneous catalyst capable of dehydrogenating H₃B·NMe₂H to [H₂BNMe₂]₂ at 0.2 mol% loading in 30 minutes at 298 K. Rapid dehydrogenation and dehydrocoupling of H₃B·NMeH₂ to form high molecular weight poly(N-methylaminoborane) with a low PDI has also been achieved. Investigations using model aminoborane H₂B=NiPr₂ and intermediate B-N species H₃B·NMe₂BH₂·NMe₂H and [H₂B·NMeH]₃ has helped establish an overall mechanistic rationale for this process.

This thesis examines the effects of coordinating highly sterically demanding and strongly electron donating saturated N-heterocyclic carbenes (NHCs) at late transition metal centres. Chapter III details the synthesis of a range of iridium complexes of the type (NHC)2IrHxCly [x = 1, 2; y = 0, 1], bearing the saturated NHCs 5-Mes, 6-Mes and 7-Mes. Unusually facile activation chemistry is observed in the reaction of [Ir(COE)2Cl]2 with 6-Mes and 7-Mes to form the doubly cyclometallated species (6-Mes')2IrH and (7-Mes')2IrH, which were fully characterised. The responses of these complexes to the addition of dihydrogen and HCl were studied, leading to the controlled synthesis of range of precursors to 14-electron iridium cations. In Chapter IV the formation of low valent iridium cations with weakly coordinating anions is targeted. Isolation of the cationic complexes [(NHC)(NHC')IrH][BArf4] and [(NHC)2IrH2][BArf4] (NHC = 6-Mes, 7-Mes) showcases the stabilising power offered by these expanded ring systems. This allowed the study the interaction of these low valent species with a range of amine-borane substrates which are known to be readily dehydrogenated. Thermodynamic data on the C-H bond activation processes occurring at these iridium centres were able to be obtained due to facile, reversible oxidative addition of C-H bonds across the 14-electron iridium. Chapter V focuses on the effects of increasing the steric bulk of these NHCs to limit the coordination of multiple ligands at the metal centre. Use of 2,6-diisopropyl-phenyl (Dipp) groups on the expanded ring NHCs, instead of mesityl groups, leads to an unprecedented mode of reactivity with [Ir(COE)2Cl]2. Activation and cleavage of C-N bonds in the carbene ring is observed, resulting in an open chain ligand chelating to the metal centre. Activation of the backbone in this manner has allowed the synthesis of saturated NHCs bearing a weakly coordinating anion on the ring. Here the first example of an anionic, saturated NHC is reported. In Chapter VI these highly sterically demanding NHCs are exploited to stabilise active species in low valent gold chemistry. The extreme steric bulk of the 6-Dipp ligand disfavours reduction of Au(I) to Au(0), however the resulting cation is observed to interact strongly with the weakly coordinating anion, [BArf4]-. Thus, attempts were made to optimise the anion and conditions to isolate a catalytically relevant intermediate. The strong donating power of these expanded ring NHCs is also exploited to activate gold hydride complexes of the type (NHC)AuH (NHC = 6-Dipp, 7-Dipp). Analogues of [H3]+ containing gold atoms ([{LAu}2H]+ and [LAuH2]+) supported by expanded ring NHCs were also targeted.

Metal and metal oxides are widely used in industry, and to optimize their performance their surfaces are commonly functionalized by the formation of thin films. Self-assembled monolayers (SAMs) are deposited on metals or metal oxides either from solution or by gas deposition. Thiols with polar terminal groups are utilized for creating the responsive surfaces which can interact electrostatically with other adsorbates. Surface charge effects wetting and adhesion, and many other surface properties. Polar terminal groups in thiols could be used to modify these factors. Mixed SAMs can provide more flexible surfaces, and could change the resulting surface properties under the influence of factors such as pH, temperature, and photo-illumination. Therefore, in order to control these phenomena by mixed polar-terminated thiols, it is necessary to understand the composition and conformation of the mixed SAMs and their response to these factors. In this work, mixtures of thiols with carboxylic and amino terminal groups were studied. Carboxylic and amino terminal groups of thiol interact with each other via hydrogen bonding in solution and form a complex. Complexes adsorb to the surface in non-conventional orientations. Unmixed SAMs from each type, either carboxylic terminated thiols or amino terminated thiols are in standing up orientation while SAMs from complexes are in an axially in-plane orientation. Selenol is an alternative to replace thiols for particular applications such as contact with biological matter which has a better compatibility with selenol than sulfur. However, the    Se-C bond is weaker than the S-C bond which limits the application of selenol. Understanding the selenol adsorption mechanism on gold surfaces could shed some light on Se-C cleavage and so is investigated in this work. Se-C cleavage happens in the low coverage areas on the step since atoms at steps have lower coordination making them more reactive than atoms on the terraces.  Another area where the self-assembly of molecules is of importance is for dye sensitized solar cells, which are based on the adsorption of the dye onto metal oxides surfaces such as TiO2.The interface between the SAM of dye and the substrate is an important factor to consider when designing dyes and surfaces in dye sensitized solar cells (DSSCs). The quality of the self-assembled monolayers of the dye on the TiO2 surface has a critical influence on the efficiency of the DSSCs.  Creation of just a monolayer of dye on the surface could lead to an efficient current of photo-excited electrons to the TiO2 and degeneration of the dye by redox. This work, T-PAC dye showed island growth with some ad-layer that is not in contact with the surface, whereas the MP13 dye adsorption is laminar growth.  Cuprite (Cu2O) is the initial and most common corrosion product for copper under atmospheric conditions. Copper could be a good replacement for noble metal as catalysts for methanol dehydrogenation. Knowledge about the structure of Cu2O(100) and Cu2O(111) surfaces could be used to obtain a deeper understanding of methanol dehydrogenation mechanisms with respect to adsorption sites on the surfaces. In this work, a detailed study was done of Cu2O(100) surface which revealed the possible surface structures as the result of different preparation conditions. Studies of the structure of Cu2O(100) and Cu2O(111) surfaces show that Cu2O(100) has a comparatively stable surface and reduces surface reactivity. As a consequence, dehydrogenation of methanol is more efficient on the Cu2O(111) surface. The hydrogen produced from methanol dehydrogenation is stored in oxygen adatom sites on both surfaces. / <p>QC 20161107</p>

The availability of kinetic data for the oxidative dehydrogenation (ODH) of n-butane from Téllez et al. (1999a and 1999b) and Assabumrungrat et al. (2002) presented an opportunity to submit a chemical process of industrial significance to Attainable Region (AR) analysis. The process thermodynamics for the ODH of n-butane and 1-butene have been reviewed. The addition of oxygen in less than the stoichiometric ratios was found to be essential to prevent deep oxidation of hydrocarbon products {Milne et al. (2004 and 2006c)}. The AR concept has been used to determine the maximum product yields from the ODH of n-butane and 1-butene under two control régimes, one where the partial pressure of oxygen along the length of the reactor was maintained at a constant level and the second where the oxygen partial pressure was allowed to wane. Theoretical maxima under the first régime were associated with very large and impractical residence times. The Recursive Convex Control policy {Seodigeng (2006)} and the second régime were applied to confirm these maxima {Milne et al. (2008)}. Lower and more practical residence times ensued. A differential side-stream reactor was the preferred reactor configuration as was postulated by Feinberg (2000a). Abstract A.D. Milne Page 4 of 430 The maximum yield of hydrocarbon product, the associated residence time and the required reactor configuration as functions of oxygen partial pressure were investigated for the series combinations of an inert porous membrane reactor and a fixed-bed reactor. The range of oxygen partial pressures was from 85 kPa to 0.25 kPa. The geometric profile for hydrocarbon reactant and product influences the residence times for the series reactors. The concept of a residence time ratio is introduced to identify the operating circumstances under which it becomes advantageous to select an inert membrane reactor in preference to a continuously stirred tank reactor and vice versa from the perspective of minimising the overall residence time for a reaction {Milne et al. (2006b)}. A two-dimensional graphical analytical technique is advocated to examine and balance the interplay between feed conditions, required product yields and residence times in the design of a reactor {Milne et al. (2006a)}.. A simple graphical technique is demonstrated to identify the point in a reaction at which the selectivity of the feed relative to a product is a maximum {Milne et al. (2006a)}. Literature Cited Assabumrungrat, S. Rienchalanusarn, T. Praserthdam, P. and Goto, S. (2002) Theoretical study of the application of porous membrane reactor to Abstract A.D. Milne Page 5 of 430 oxidative dehydrogenation of n-butane, Chemical Engineering Journal, vol. 85, pp. 69-79. Feinberg, M. (2000a) Optimal reactor design from a geometric viewpoint – Part II. Critical side stream reactors, Chemical Engineering Science, vol. 55, pp. 2455-2479. Milne, D., Glasser, D., Hildebrandt, D., Hausberger, B., (2004), Application of the Attainable Region Concept to the Oxidative Dehydrogenation of 1- Butene in Inert Porous Membrane Reactors, Industrial and. Engineering Chemistry Research, vol. 43, pp. 1827-1831 with corrections subsequently published in Industrial and Engineering Chemistry Research, vol. 43, p. 7208. Milne, D., Glasser, D., Hildebrandt, D., Hausberger, B., (2006a), Graphical Technique for Assessing a Reactor’s Characteristics, Chemical Engineering Progress, vol. 102, no. 3, pp. 46-51. Milne, D., Glasser, D., Hildebrandt, D., Hausberger, B., (2006b), Reactor Selection : Plug Flow or Continuously Stirred Tank?, Chemical Engineering Progress. vol. 102, no. 4, pp. 34-37. Milne, D., Glasser, D., Hildebrandt, D., Hausberger, B., (2006c), The Oxidative Dehydrogenation of n-Butane in a Fixed Bed Reactor and in an Inert Porous Membrane Reactor - Maximising the Production of Butenes and Butadiene, Industrial and Engineering Chemistry Research vol. 45, pp. 2661-2671. Abstract A.D. Milne Page 6 of 430 Milne, D., Seodigeng, T., Glasser, D., Hildebrandt, D., Hausberger, B., (2008), The Application of the Recursive Convex Control (RCC) policy to the Oxidative Dehydrogenation of n-Butane and 1-Butene, Industrial and Engineering Chemistry Research, (submitted for publication). Seodigeng, T.G. (2006), Numerical Formulations for Attainable Region Analysis, Ph.D. thesis, University of the Witwatersrand, Johannesburg, South Africa. Téllez, C. Menéndez, M. Santamaría, J. (1999a) Kinetic study of the oxidative dehydrogenation of butane on V/MgO catalysts, Journal of Catalysis, vol. 183, pp. 210-221. Téllez, C. Menéndez, M. Santamaría, J. (1999b) Simulation of an inert membrane reactor for the oxidative dehydrogenation of butane, Chemical Engineering Science, vol. 54, pp. 2917-2925. __________________________________

Maneiras de se produzir hidrogênio limpo e combustíveis alternativos para uso em células a combustível têm sido um dos grandes desafios na busca por fontes de energia limpas e renováveis. Recentemente, foi desenvolvido em nosso laboratório um sistema em que o etanol é desidrogenado em um reator acoplado à uma célula a combustível de troca protônica (PEMFC) e o hidrogênio resultante dessa reação foi utilizado como combustível. No entanto, houve uma perda de densidade de potência da célula que, em 0,7 V, foi de 40% em relação à de uma célula alimentada com hidrogênio puro. O motivo dessa perda de desempenho ainda não foi elucidado, sendo este o foco do estudo realizado neste trabalho. Pesquisas sobre a contaminação de células PEM por várias impurezas, como por exemplo, CO, metanol, ácido fórmico, etc., já têm sido realizadas, mas, até o momento, nenhum estudo foi encontrado sobre a influência dos subprodutos da reação de desidrogenação do etanol (acetato de etila, acetaldeído e etanol não reagido) no desempenho destes sistemas. Além disso, devido à ausência de CO2, o hidrogênio produzido teria grande potencial para ser utilizado em células de membrana de troca aniônica (AEMFC) e, portanto, a realização de estudos sobre a influência desses contaminadores sobre o desempenho desse tipo de célula também é altamente relevante. Diante disso, neste trabalho, desenvolveu-se uma nova vertente de pesquisa, onde o hidrogênio foi contaminado pelos subprodutos em questão e as influências destes contaminadores sobre os desempenhos das PEMFC e AEMFC foram estudadas. No caso da AEMFC, por não haver membranas e, especialmente, ionômeros comerciais que resultem em células com altas densidades de potência, buscou-se sintetizar esses materiais antes dos estudos das contaminações. Através da análise por diferentes técnicas, foi possível esclarecer que o etanol não reagido é o principal veneno no caso das PEMFCs, sendo que o acetaldeído e o acetato de etila têm contribuições menores para o envenenamento. Foram testados diferentes eletrocatalisadores nos eletrodos a fim de se obter melhores desempenhos, sendo que o melhor resultado foi observado quando se utilizou o catalisador de Pt-Co/C no cátodo da célula (e Pt/C no ânodo), sendo que em 0,7 V a perda em densidade de potência foi de apenas 20% em comparação à uma célula alimentada por H2 puro e com Pt/C ambos os eletrodos. No caso da AEMFC, foi possível se obter ionômeros inéditos que combinados com as membranas sintetizadas, resultaram em células com densidade de potência máxima acima de 1 W cm-2. No entanto, devido à instabilidade química, ao serem expostos aos contaminadores, os materiais parecem sofrer degradação, que leva à perda quase total e irreversível do desempenho da célula. / The development of methods to produce clean hydrogen and alternative fuels for fuel cells has been a big challenge in the search of clean and renewable electric energy sources. Recently, a system was developed in our laboratory where ethanol was dehydrogenated in a reactor coupled to a proton exchange membrane fuel cell (PEMFC) and the hydrogen produced from this reaction was used as fuel. However, a loss of 40% in power density of the cell was observed at 0.7 V when compared to a cell fed with pure hydrogen. The reason for this loss of performance was not elucidated and this is a focus of the study involved in this work. Researches on the effect of contamination of PEM cells by various impurities, such as CO, methanol, formic acid, etc., have already been made, but so far, nothing has been found about the influence of the byproducts of the ethanol dehydrogenation reaction (ethyl acetate, acetaldehyde and unreacted ethanol) in fuel cells performances. Moreover, because of the absence of CO2, the hydrogen produced in such dehydrogenation reactor could have a great potential for applications in anion exchange membrane fuel cells (AEMFC), making the characterization of the influence of these contaminants in the performance of such systems of high relevance. In this context, in this work a new research strand was developed, where hydrogen was contaminated by the by-products of the ethanol dehydrogenation and their influences on the performances of PEMFC and AEMFC were investigated. In the case of AEMFC, because of the lack of commercially available membranes and ionomers that lead to high power densities, it was necessary to synthesize these materials before the contamination studies. Through the analysis by different techniques, it was possible to clarify that unreacted ethanol is the main poison in the case of PEMFCs, with acetaldehyde and ethyl acetate having minor contributions. Different catalysts were tested in order to obtain better fuel cells performances and the best result was achieved when the Pt-Co/C catalyst was used at the cathode of the cell (with Pt/C at the anode), for which the loss of power density was only 20% compared to a cell fed by pure H2 and with Pt/C on both electrodes (working at 0.7 V). In the case of the AEMFC, new ionomers were obtained that combined with the synthesized membranes resulted in cells with a maximum power density above 1 W cm-2. However, due to the chemical instability, when exposed to contaminants, these materials appear to undergo degradation, leading to almost total and irreversible losses of the cell performance.