Process options to minimise the environmental impact and improve the efficiency of biodiesel production have been investigated. The process options considered include the use of heterogeneous catalysts and used cooking oil (UCO). An esterification pre-treatment reaction was investigated using an ion-exchange resin (Purolite D5082) and an immobilised enzyme (Novozyme 435). Another immobilised enzyme (Amano Lipase PS-IM) was investigated for transesterification. The fresh and used catalysts have been characterised. The catalytic activity of Purolite D5082, Novozyme 435 and Amano Lipase PS-IM have been investigated using a jacketed batch reactor with a reflux condenser. Purolite D5082 has been developed for the esterification pre-treatment process and is not commercially available. Novozyme 435 has been shown to be an effective esterification catalyst for materials with high concentrations of free fatty acid but it has not been investigated for the esterification pre-treatment reaction. It was found that a high conversion was possible with both catalysts. The optimum reaction conditions identified for Purolite D5081 were a temperature of 60 C, a methanol to free fatty acid (FFA) mole ratio of 62:1, a catalyst loading of 5 wt% resulting in a FFAs conversion of 88% after 8 h of reaction time. The optimum conditions identified for Novozyme 435 were a temperature of 50 C, a methanol to FFA mole ratio of 6.2:1 and a catalyst loading of 1 wt% resulting in a conversion of 90% after 8 h of reaction time. These catalysts were compared to previously investigated Purolite D5081 and it was found that the highest conversion of 97% was achieved using Purolite D5081, however there were benefits to using Novozyme 435 because the reaction could be carried out using a much lower mole ratio, at a lower temperature and in much shorter reaction time. During the Novozyme 435 catalysed esterification pre-treatment reactions it was found that the amount of free fatty acid methyl esters (FAME) formed during the reaction was greater than the amount of FFAs consumed. In order to investigate further an ultra-performance liquid chromatography mass spectrometry (UPLC-MS) method was developed to monitor the monogclyeride (MG), diglyceride (DG) and triglyceride (TG) concentrations. This analytical method was used to show that Novozyme 435 would catalyse the esterification of FFAs as well as the transesterification of MGs and DGs typically found in UCO. With the UPLC-MS method it was possible to separate the 1, 2 and 1, 3 DG positional isomers and from this it could be seen that the 1, 3 isomer reacted more readily than the 1, 2 isomer. The results from the UPLC-MS method were combined with a kinetic model to investigate the reaction mechanism. The kinetic model indicated that the reaction progressed with the sequential hydrolysis esterification reactions in parallel with transesterification. Commercially available Amano Lipase PS-IM was investigated for the transesterification reaction. Enzymes are not affected by FFAs and as a result the optimisation was carried out with UCO as the raw material. An optimisation study for the transesterification of UCO with Amano Lipase PS-IM has not previously been reported. The conditions identified for the Amano Lipase PS-IM catalysed transesterification step are addition of 5 vol% water, a temperature of 30 C, a methanol to UCO mole ratio of 3:1 and a catalyst loading of 0.789 wt% resulting in a TG conversion of 43%. An overall enzyme catalysed process was proposed consisting of Amano Lipase PS-IM catalysed transesterification (stage 1) followed by Novozyme 435 catalysed esterification (stage 2). The previously identified optimum conditions identified for each catalyst were used for above stages. It was found that when the oil layer from stage 1 was dried the final TG conversion was 55%.

Thesis (Ph.D.)--University of Delaware, 2006. / Principal faculty advisor: Jochen Lauterbach, Dept. of Chemical Engineering. Includes bibliographical references.

No description available.

With continually increasing concern over anthropogenic carbon dioxide emissions and their effect on global climate, the search for alternative fuels, especially for mobile applications such as in vehicles, is of immediate concern. Herein, research towards hydrogen as an alternative energy carrier is discussed; first, with the investigation of “hybrid” hydrogen storage systems that are meant to provide hydrogen for a fully fuel cell powered vehicle via a chemical reaction; and second, that of a thermally regenerative fuel cell system (TRFC) to partially supplant the energy needs of transport trucks by harnessing engine waste heat. Hybrid storage systems are comprised of a heterocyclic carrier that undergoes endothermic hydrogen release (indoline) and an organic hydride that undergoes exothermic release (amine boranes). Different embodiments are considered, varying in the mechanism of exothermic release (thermolysis vs. hydrolysis) and the mode of combination (physical vs. chemical). A thorough investigation into the effect of catalyst, sterics and temperature on the heterogeneously catalyzed dehydrogenation rate of N-heterocycles was executed. A number of trends with respect to the catalyst identity and the level of steric protection around the nitrogen atom were observed. The study towards a TRFC involved an investigation of the heterogeneous hydrogenation of benzylic ketones. Screening of a myriad of different catalysts was performed, including those with various supports, metals and modifications, and the examination of how both the sterics and electronics of the ketone affect the hydrogenation rate. A rapid hydrogenation at relatively low metal loadings and hydrogen pressures with extreme selectivity (>99.9%) is required. To date, however, such a combination has been elusive. The best selectivity was obtained with commercial Pd/SiO2 (99.99%), yet at a low conversion of 6%, after 1 h under 1 atm of H2 at 100 ˚C. In addition to the poor conversion, SiO2 is not electronically conductive and is therefore not fit for this application. The best viable catalyst, then, was a Pd/Vulcan XC-72 (carbon) catalyst made by the author with an observed 14% conversion and 98% selectivity under the same conditions. However, trends in activity and selectivity with respect to the catalyst and ketone have been characterized herein. / Thesis (Ph.D, Chemistry) -- Queen's University, 2012-05-23 13:37:53.172

Os-Zn-Al hydrotalcite-like compounds (HTlc’s) were synthesised by the co-precipitation method and characterised using different techniques (powder XRD, ICP-OES, FT-IR spectroscopy, BET-surface area measurements, SEM and SEM-EDS, cryo-TEM, 27Al SS-NMR and TGA-DSC). The hydrotalcite-like catalyst was used to heterogenise the aminohydroxylation reaction. Among the three solvents investigated (toluene, MeCN/water (1:1 v/v) and t- BuOH/water (1:1 v/v)) in the aminohydroxylation reaction, toluene showed the slowest reaction rate, MeCN/water (1:1 v/v) and t-BuOH/water (1:1 v/v) demonstrated fast reaction rates comparable to each other. The reaction temperature was only significant when toluene was used as the solvent system (reaction time (100% depletion of starting material) and temperature are inversley proportional). The catalyst HTlc structure demonstrated a significant effect in terms of the reaction time and isolated yield of the -amino alcohols. Under the same testing conditions a heat treated catalyst (non-HTlc) showed a shorter reaction time, a reduction in the isolated yield of -amino alcohols with a rise in diol formation. All the different classes of olefins (aliphatic, aromatic, and functionalised) that were tested, gave 99.99% depletion of starting material. However, due to the same purification difficulties encountered in the homogeneous amino hydroxylation (AA) reaction, the isolated yield of -amino alcohols achieved here, ranged from 13 to 35 %, with the highest yield (35%) obtained when methylcinnamate was used as the olefin. Characterisation of the spent catalyst showed that HTlc structure is maintained, but crystallinity was lost (the material becomes polycrystalline) after the reaction. The leaching test showed that 4.5% and 5.5% of Os leached from the catalyst to the reaction solution when MeCN/water (1:1 v/v) and t-BuOH /water (1:1 v/v) were used as the solvent system, respectively. The leached form of Os was determined to be inactive, indicating that this system is truly heterogeneous. The recycling study (three cycles) indicated that the catalyst can be recycled, but with a decrease in the reaction rate (which could be due to structure defects and loss of crystallinity), and with no significant difference in the isolated yield of the amino-alcohol. The crystal structure of three -amino alcohols are also reported. The crystal structure of the - amino alcohol of cyclohexene, methylcinnamte and t-butylcrotonate were needle-like triclinic, pi, needle-like monoclinic, p21/c and cubic-like triclinic, p-1, respectively. / Thesis (M.Sc.)-University of KwaZulu-Natal, Durban, 2010.

Copper is an inexpensive, earth-abundant, non-toxic metal that is found to have widespread applications in catalysis. Ullmann and Ullmann-type reactions and Glaser-Hay oxidative coupling of terminal alkynes are some of the well-established copper catalyzed coupling reactions used for the construction of important organic molecules, including pharmaceuticals, commodity chemicals and polymers. Those reactions have been mainly performed homogeneously, where the removal of residual copper from the reaction mixture is a challenge. Therefore, many researchers tried supporting copper precatalysts in order to help recover, and thus reduce final product contamination. Some studies showed that copper leached significantly from the support, with others showing that leached copper has a role in the catalysis. Nevertheless, many studies reported that the used supported catalysts were recyclable and claimed catalyst's heterogeneity. In most cases, the nature of the truly active copper species is still not clear. The objectives of this thesis were (1) to assess the heterogeneity/homogeneity of active copper species in popular catalytic C-N coupling reactions with already studied catalysts, mainly a copper exchanged zeolite and copper oxide nanoparticles, and (2) to use the collected information in designing a truly heterogeneous (stable and recyclable) catalyst. Initially, and because of its shape selectivity characteristics, copper-exchanged NaY zeolite, Cu(II)Y, was chosen to study the heterogeneity of copper catalyzed amination of aryl iodide with imidazole. The collected results from conducted shape selectivity tests indicated that Cu(II)Y might be heterogeneous catalyst, but because of the used base, that is crucial for this C-N coupling reaction, the crystallinity of the zeolite structure was diminished. Therefore, it was important to support copper on a framework that is stable under the basic conditions required for this type of reaction if a heterogeneous, recyclable catalyst were to be achieved. For this purpose, cerium oxide was chosen, and copper oxide supported on cerium oxide, CuO-CeO₂, was investigated as a potential heterogeneous catalyst for C-N coupling reaction. This investigation included the role of each reaction reagent in facilitating copper leaching into solution. It was found that copper leached from the support and it was demonstrated through hot filtration tests that the leached copper species was the main active catalyst. Leaching was caused by the solvent (DMSO) as well as the used reactants and the base. Similar conclusions were drawn when this CuO-CeO₂ catalyst was used for the direct synthesis of imines from amines under aerobic conditions. Although this CuO-CeO₂ catalyst has the advantages of being more recoverable and active than unsupported CuO nanoparticles at similar copper loadings, it is not fully recyclable, as the copper catalysis occurs in solution. These findings meant that designing a truly heterogeneous catalyst for this reaction is a challenging task. Understanding the effect of each individual factor of this complicated system might help in achieving the second goal - designing a truly heterogeneous catalyst. Therefore, further studies were carried out to understand the effect of reaction conditions, including temperature, base, support, and solvent, on copper leaching. Homocoupling of terminal alkynes was chosen as a model reaction for this study, and CuO was supported on TiO₂ (10CuO-TiO₂) and on γ-Al₂O₃ (10CuO-Al₂O₃). It was found that copper interaction with the support affects the extent of leaching as well as the nature and activity of leached species. High temperature also facilitates copper leaching especially when a ligating amine, like piperidine, is present in the system.

Thesis (Ph. D.)--University of Virginia, 2007. / Includes bibliographical references. Also available online through Digital Dissertations.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / As pilhas a combustível são uma alternativa para gerar energia sem poluir o meio ambiente. Elas produzem energia elétrica pela reação do hidrogênio com o oxigênio do ar. O produto da reação é a água. É uma forma de geração de energia bastante interessante por ser uma tecnologia limpa. O hidrogênio utilizado como combustível para as pilhas a combustível, proveniente da reforma a vapor de hidrocarbonetos, contém cerca de 1% de monóxido de carbono. O hidrogênio, usado como combustível para pilha a combustível de membrana polimérica eletrolítica (PEMFC), não pode conter mais de 10 ppm de monóxido de carbono. A presença de monóxido de carbono em concentrações acima de 10 ppm envenena o anodo de Pt da célula. Neste trabalho foram estudados catalisadores que podem ser usados para oxidar monóxido de carbono seletivamente na presença de hidrogênio. Os catalisadores estudados para a oxidação seletiva de CO foram: 1%Pt/Al2O3, 1%Pt-1%Cu/Al2O3, 1%Pt/Nb2O5, 1%Pt-1%Cu/Nb2O5, 1%Cu/Al2O3, 1%Cu/Nb2O5, Al2O3 e Nb2O5. Os catalisadores suportados em Nb2O5 apresentaram melhor seletividade em relação aos catalisadores suportados em Al2O3 devido ao efeito de interação metal-suporte (SMSI) dos catalisadores suportados em Nb2O5 que diminuiu a adsorção dissociativa do H2. A adição do Cu promoveu a reação de oxidação do CO, aumentando a seletividade para a formação do CO2 devido à interação da Pt com o Cu. Os catalisadores à base de Pt testados apresentaram 100% de conversão de CO a CO2 em torno de 100C. Melhores resultados foram obtidos quando os catalisadores foram reduzidos a 300C, a seletividade dos catalisadores foi menor quando reduzidos a 500C. A seletividade foi de 47% para o catalisador Pt/Al2O3, 58% para o catalisador PtCu/Al2O3 e de 54% para o catalisador Pt/Nb2O5. O catalisador PtCu/Nb2O5 reduzido a 300C apresentou a melhor seletividade entre os catalisadores testados, em torno de 64%, tanto pela interação bimetálica da platina com o cobre quanto pela interação da fase ativa com o suporte. Os óxidos Al2O3 e Nb2O5 apresentaram 100% de conversão de CO embora a temperatura de ignição tenha sido maior em relação aos catalisadores à base de Pt, a Al2O3 apresentou 25% de seletividade enquanto que a Nb2O5 apresentou 49% de seletividade. O catalisador Cu/Al2O3 não apresentou atividade para a oxidação seletiva de CO. Já o catalisador Cu/Nb2O5, quando ativado a 300C, apresentou 100% de conversão de CO em torno de 230C com 40% de seletividade. / The fuel cells are an alternative to generate energy without polluting the environment. They produce electric energy through the reaction of hydrogen with the oxygen from air. The product of the reaction is water. It is an interesting form of generation energy because its a clean technology. The hydrogen used as combustible for the fuel cells is proceeding from the steam reform hydrocarbons, this hydrogen contains about 1% of carbon monoxide. The hydrogen, used as combustible for the polymer electrolytic membrane fuel cell (PEMFC), can not contain more than 10 ppm of carbon monoxide. The presence of carbon monoxide in concentrations above 10 ppm poisons the anode of Pt of the cell. In this work it was studied catalyst that can be used to oxidize carbon monoxide selectively in the presence of hydrogen. The catalysts studied for the selective oxidation of CO had been: 1%Pt/Al2O3, 1%Pt-1%Cu/Al2O3, 1%Pt/Nb2O5, 1%Pt-1%Cu/Nb2O5, 1%Cu/Al2O3, 1%Cu/Nb2O5, Al2O3 and Nb2O5. The catalysts supported on Nb2O5 had better selectivity in relation to the catalysts supported in Al2O3 due to the strong metal-support interaction effect (SMSI) that occurs in the catalysts supported in Nb2O5. The addition of the Cu promoted the reaction, increasing the selectivity for the oxidation of the CO due to the interaction of the Pt with the Cu. The Pt based catalysts had 100% of CO conversion to CO2 around 100C. Better results had been gotten when the catalysts were reduced at 300C, the selectivity of the catalysts was lesser when reduced at 500C. The selectivity was 47% for the Pt/Al2O3 catalyst, 58% for the PtCu/Al2O3 catalyst and 54% for the Pt/Nb2O5 catalyst. The PtCu/Nb2O5 catalyst reduced at 300C presented the best selectivity among the tested catalysts, around 64%, as much for the bimetallic interaction of platinum with copper how much for the interaction of the active phase with the support. The oxides Al2O3 and Nb2O5 had presented 100% of CO conversion even though the ignition temperature had been lesser in relation to the Pt based catalysts, the Al2O3 presented 25% of selectivity while that the Nb2O5 presented 49% of selectivity. The Cu/Al2O3 catalyst did not present activity for the selective oxidation of CO already the Cu/Nb2O5 catalyst, when activated 300C, it presented 100% of CO conversion around 230C with 40% of selectivity.