Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 55 for “"product selectivity"”.
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Elucidating the Reactivity of Cytochrome P460: Maturation, Product Selectivity, and Substrate Scope
Ammonia oxidizing bacteria (AOB) have evolved a nitrogen-based metabolism in which they rely solely on the oxidation of ammonia as their energy for life. In contrast to carbon-based metabolisms, there is a large gap in our knowledge of nitrogen-based metabolisms. The primary energy producing step …
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Oxygenates in iron Fischer-Tropsch synthesis : is copper a selectivity promoter?
… promoted with potassium in order to enhance the product selectivity, while copper is added as a reduction promoter which increases the reduction rate and decreases the reduction temperature of the iron catalyst. The effect of copper on the product selectivity however, remains unclear. This study …
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Trends in C-H bond dehydrogenation energetics for small molecule conversion
… few decades. The design of materials to maximize product selectivity for wide–ranging energy and environmental applications is typically carried out by a creating of small library of materials. Optimal catalysts are identified by a series of measurements, and in most cases the underlying reaction …
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The performance of structured cobalt catalysts in Fischer-Tropsch synthesis
Cobalt is the preferred catalyst metal for the production of clean burning, high cetane number diesel fuel from synthesis gas using the Fischer-Tropsch synthesis. Hence, increasing C5+ selectivity of cobalt catalysts is one of the hot topics in Fischer-Tropsch synthesis. Internal mass transport …
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Elucidation of nitrate reduction mechanisms on a Pd/In bimetallic catalyst using isotope labeled nitrogen species
… ion exchange regenerant brines requires improved selectivity for the end-product dinitrogen (N2) over toxic ammonia species (NH4+, NH3). A key to improving N2 versus NH4+ production is to elucidate nitrate reduction pathways and identify the key intermediate(s) that determine selectivity. To …
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Design and Synthesis of Metal Nanostructures for Plasmon-Enhanced Catalysis
… of catalysts and parasitic formation of by-products. Light is used as an alternative energy input to drive chemical reactions on semiconducting photocatalysts, but the slow reaction rates and insufficient control of product selectivity hinder wide adaptation of photocatalysis. Plasmonic …
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Bimetallic Catalyst for Lignin Depolymerization
… biofuels and multiple valuable chemical products with reduced greenhouse gas emissions. Lignin is the second abundant biopolymer source in nature and is found almost everywhere. Since the 1950’s, there have been reports of lignin depolymerization research to develop valorization …
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Carbidization and size effects of unsupported nanosized iron in the low temperature Fischer-Tropsch process
In the process of developing the most efficient production of fuels from coal or natural gas, there have been major advances in the development of the catalysts used. Previous work at the Centre for Catalysis Research, at the University of Cape Town, has shown great potential and provided a much …
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Thermochemical conversion of high-density polyethylene (HDPE) to value-added products using cobalt-based catalysts
… inert atmosphere to convert HDPE into valuable products, such as wax, oil, gas, and char. The current thesis explores the utilization of cobalt-based catalysts in the HDPE pyrolysis. The study investigates the effects of cobalt loadings in Co3O4/Al2O3 catalysts and reveals that an increase in …
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Non-noble metal nanocatalysts for the purification and reduction of carbon dioxide
… catalytic systems with inherent benefits (e.g., product selectivity, mass activity, and cost). This thesis contains two parts: first on the development of nanomaterial systems for the purification of CO2 from flue gas by the catalytic reduction of oxygen (O2) and second on the design of novel …
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Perovskites as New Support Materials for the Iron Based Fischer-Tropsch Synthesis
In the Fischer-Tropsch process, valuable products consisting mainly of long chain hydrocarbons and water as by-product are synthesized from the basic starting materials hydrogen and carbon monoxide, derived from sources such as coal, gas or biomass [1]. Iron catalysts and cobalt based systems are …
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Molecular Hybrid Photocathodes Based on Silicon for Solar Fuel Synthesis
… carrier (e.g. H$_{2}$ and CO$_{2}$-reduction products from H$_{2}$O and CO$_{2}$). However, molecular catalyst-based photocathodes remain scarcely reported and typically suffer from low efficiencies and/or stabilities due to inadequate strategies for interfacing the molecular component with the …
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Photoelectrochemical and Chemoenzymatic Reforming for Sustainable Fuel Production
… driven by renewable energy sources for the production of clean fuels and commodity chemicals from diverse waste feedstocks is an appealing approach towards creating a circular economy. Over the years, semiconductor photocatalysts based on TiO₂, CdS, carbon-nitrides (CNx) and carbon dots …
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I. The Catalytic Oxidation of Olefins by a Cobalt Complex. Ii. The Thermodynamics of Base Binding to a Cobalt Complex (Cosmdpt)
… catalysts are used to improve the rate and/or selectivity of such oxidations. Many homogeneous oxidations catalyzed by transition metal complexes, especially those containing first row transition metals, proceed by autoxidation. Since this is a free radical chain reaction the reaction generally …
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The oligomerization of propene over nickel synthetic mica-montmorillonite
… propene oligomerization than SMM, although the product selectivity (60% of the oligomers boiled at above 453 K) is similar. The increase in activity of NiSMM is attributed to an increase in the surface acidity of the catalyst. The maximum activity over the nickel exchanged catalyst occurs at a …
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ZnSe Quantum Dots as a platform for solar fuels synthesis
… after 1000 min of irradiation with a CO (vs. H2) selectivity of > 40%. This hybrid photocatalyst showed a distinct induction period which was assigned to slow initial Co(III) to Co(II) reduction and can be accelerated by priming the catalyst in ascorbic acid solution. The insights demonstrate that …
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The effect of temperature on the Fischer-Tropsch selectivity and further mechanistic insights
… the enhanced recovery of conventional oil, the production of extra-heavy oil / tar sands and the utilization of alternative energy production technologies (technologies other than crude oil refining). The Fischer-Tropsch Synthesis (FTS) discovered in 1923 by Fischer and Tropsch, is one of these …
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Probing the Role of Amines in Aqueous Electrochemical Reduction of Captured-state CO₂
… steric hindrance and pKₐ, impact speciation, product selectivity, and cell performance. We chose a subset of primary alkylamines with varied steric hindrance and pKₐ and evaluated each on the basis of Faradaic efficiency, partial current density to reduced products, and the dynamics of product …
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Development of a Kinetic Model for Low Temperature Fischer-Tropsch Synthesis
… of CO and H2, is converted to hydrocarbon products ranging from methane to wax when low temperature conditions are used. Subsequent product upgrading steps allow high quality liquid fuels to be obtained which are clean burning. This will help to mitigate the impact of human activity on the …
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Elemental and structural behaviors of bimetallic nanoparticles under reactive environments and its implication in catalyst design, processing, and performance
… it affects performance, with more emphasis on product selectivity. The two model systems are metal-on-metal Rh-on-Pd for CO2 hydrogenation and Cu@CuAg nanocatalyst for propylene epoxidation. Environmental transmission electron microscopy was utilized in most of the projects mentioned above and …
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