No description available.

<p> The thermolysis of 2-diphenylmethylenehydrazono-5,5-dimethyl-Δ^3-1,3,4-oxadiazoline in vacuum and in chlorobenzene was studied. In both cases a stable 1-(diphenylmethylene)-4, 4-dimethyl-3-oxo-1,2-diazetidinium inner salt was obtained as the major product. The corresponding imino-oxirane, an isomer of the diazetidinium inner salt, is believed to be a precursor of the above product. Thermolysis of the same oxadiazoline in methanol gave benzophenone methyl carbazate and methyl isopropyl ether, probably involving the initial formation of an isocyanate as an intermediate.</p> / Thesis / Master of Science (MSc)

No description available.

published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

The research presented in this dissertation involved characterization of the Cu/ZnO solid catalyst system as applied to methanol/steam reformation. Thermogravimetry was used to investigate in-lab synthesized samples and a commercial product G66B (Cu/ZnO 33/67 wt. %). The 33% Cu sample contained Cu ions in the ZnO matrix. This phase required the highest temperatures (400°C) for H₂ reduction. The 50% Cu sample reduced at a lower temperature (220°C) but its complete reduction required the same maximum temperature. The higher temperature process was similar to the 33% case, while the lower one was due to the reduction of a amorphous CuO phase. The 66% Cu sample reduced in a fairly narrow low temperature (270°C) range. Therefore, its CuO phase has a amorphous structure. G55B reduced at lower temperatures than the in-lab samples. This difference is possibly due to different synthetic procedures used in the production of G66B and the in-lab samples. The CuO phase of G66B appears to be amorphous and well dispersed. Raman spectroscopy was used to identify the crystal phases of these solids. The complexity of the initial precipitate was monitored versus the Cu/Zn ratio of the system. The nature of the phases present under reduction conditions was determined. This information has provided insight into the active phases involved in methanol reformation. The role of the solids lattice oxygen was determined. The reaction was carried out on labelled ¹⁸O-containing Cu/ZnO. Incorporation of ¹⁸O into both CO₂ and H₂O clearly indicates the involvement of these oxygens in the reaction. Observation of C¹⁸O¹⁸O indicates that the C-O bond in methanol does not remain intact. XPS was used to determine the effects of oxidation, reduction, and reaction on the Cu component of G66B. Upon oxidation all Cu exists as Cu⁺². The catalyst always contains Cu⁺¹ and Cuᵒ after H₂ reduction. After methanol/steam reformation with a 50/50 vol% mxiture, all Cu is reduced to Cuᵒ. Changes in the Cu/Zn ratio of the surface are interpreted in terms of changes in surface morphology.

No description available.

This thesis described the development of new catalytic system for the conversion of natural gas (methane) to liquid products such as methanol and formaldehyde. This technology can allow the exploitation of small and medium size gas fields without the need to build an expensive gas to liquid plants or long pipelines. The technology is based on a concept of non-separating membrane reactor where an inorganic membrane paper serves as a catalyst support through which a reaction mixture is flowing under mild conditions and short residence times.

A dissertation submitted to the Faculty of Science, University of the Wtlwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science / This dissertation focusses on the deactivation of SAP0-34 and modified SAPOs during methanol conversion under various conditions, in comparison to H-ZSM-5. SAPO-34 was found to deactivate rapidly during methanol conversdon. This was shown by the decrease in activity, surface area and pore volume of the catalyst. The deposited "coke" was analysed by in situ diffuse reflectance infra-red Fourier Transform spectroscopy,solid-state magic angle spinning nuclear magnetic resonance, gas chromatography mass spectroscopy (GCMS) of the HF- and dichloromethane-extracted to "coke"; and GCMS of the organic specfes released during regeneration of the catalyst and trapped in resin capillary inlet tubes.The "coke" consisted of alkylated aromatics and naphthalenes which probably formed on the surface or in the large cavities of SAPO-34. The amount of "coke" deposited during methanol conversion increased with reaction temperature, decreased with dilution of the methanol with water or nitrogen. and decreased with increased pressure, Incorporation of Ni into the SAPO framework did not decrease the rate of deactivation, but the "coke" that Has deposited was less bulky than that deposited in SAPO-34. Modification of the SAPO-34 with trlmethyl silylchloride decreased the rate at deactivation of the catalyst. / AC 2018

No presente trabalho foram preparados eletrodos recobertos com filmes contendo Pt, Ru e Sn pelo método de decomposição térmica de precursores poliméricos sobre um substrato de Ti. Este método permitiu a obtenção de filmes homogêneos e com estequiometria controlada. Foram avaliadas as variáveis relacionadas ao processo de preparação dos eletrodos tais como, temperatura de calcinação e proporções entre os óxidos. As caracterizações estrutural e morfológica dos eletrodos foram feitas pelas técnicas de Difração de Raios-X e Microscopia Eletrônica de Varredura. A atividade eletrocatalítica dos eletrodos foi avaliada pelas técnicas de Voltametria Cíclica, Cronoamperometria, Espectroscopia de Infra-Vermelho in situ e aplicação dos eletrocatalisadores em célula a combustível. Os resultados obtidos indicaram que o método utilizado proporcionou a preparação de eletrodos com alta área superficial devido a formação de uma morfologia contendo poros e trincas. Os eletrodos preparados com a adição de rutênio e estanho à platina apresentaram maior eficiência catalítica para a oxidação das moléculas em estudo em relação aos eletrodos contendo somente platina. Através dos espectros obtidos por FTIR in situ foi possível observar a formação espécies de CO adsorvido à superfície eletródica no potencial a partir de 100 mV (ERH) e CO2 foi produzido a partir de 400 mV (ERH). Estes valores de potencial observados são inferiores aos valores para os eletrodos de Pt pura e confirmam a contribuição do Ru para a oxidação das espécies adsorvidas que bloqueiam a superfície. Para a aplicação em células a combustível, foram preparados dois tipos de catalisadores (suportados e não suportados em pó de carbono), sendo que os catalisadores suportados apresentaram maior densidade de potência em relação aos não suportados. A composição contendo 60 % de Pt apresentou maior desempenho, confirmando os resultados obtidos em meia célula. O método de preparação do catalisador utilizado permitiu, portanto, a síntese de materiais possíveis de serem utilizados em células a combustível de metanol. / In this work we prepared electrodes containing Pt, Ru and Sn on the Ti substrate by thermal decomposition of polymeric precursors. This method yielded homogeneous films with controlled stoichiometry. The parameters of the preparation process like temperature and oxide composition were investigated. The structural and morphological material characterization were performed by X-ray Diffractometry and Scanning Electronic Microscopy. The electrocatalytic activity was investigated by Cyclic Voltammetry, Chronopotentiometry, in situ Infra-Red Spectroscopy and Fuel Cell tests. The obtained results showed that the preparation method lead to electrodes with a high surface area due to the formation of a cracked and porous morphology. The electrodes containing Ru, Sn and Pt presented the higher catalytic efficiency for the oxidation of small organic molecules than the electrodes of pure platinum. The FTIR spectra allow us to observe the formation of adsorbed CO species in potentials from 0.1 V vs RHE potential values and CO2 for potentials ranging from 0.4 V vs RHE. These values are lower than the expected for pure Pt and confirm the role of Ru in the oxidation of strongly adsorbed intermediates. In the Fuel Cell tests, it were prepared two types of catalysts (carbon supported and non supported catalysts). The carbon supported catalysts presented higher power density than the non-supported catalysts. The electrodes containing 60 % mol of Pt showed the high performance which confirms the results obtained in half cell experiments. The employed preparation method permitted the synthesis of materials that presented good possibilities for the application in Direct Methanol Fuel Cells.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.