Bochum, University, Diss., 1999.

The Fischer-Tropsch (FT) synthesis reaction is an increasingly valuable tool that produces very clean alternative fuels for the transportation and other industries. By utilizing a ready supply of syngas (H2 and CO mixture) from coal, natural gas, or a biomass source, the catalyzed reaction looks to be a promising alternative which could potentially end dependency on imported petroleum. The supercritical phase FT synthesis reaction has shown, in numerous other studies, to possess superior heat transfer capabilities, high desorption rates from the catalyst surface (enhancing catalyst life), and overall high mass transfer rates of hydrocarbon products, when compared with conventional gas and liquid phase results. Prior studies at SIUC have shown that the use of supercritical CO2 as a medium for the Fischer-Tropsch (FT) synthesis reaction enhances reaction rates while suppressing excess CO2 production. This phenomena was observed in gas phase batch reactions, meaning never before has a continuous flow FT synthesis with analysis of the liquid product distribution been attempted while using CO2 as the supercritical-phase medium. This project verifies the conclusions in a continuous flow mode, allowing for the collection and analysis of a liquid fraction. Additionally, this study evaluates the changes in the liquid product distribution for a variation of operating pressures including supercritical-phase reaction conditions, using pressures of 350, 800, 1000, and 1200psi and temperatures of 250, 300, and 350°C. The findings show that the influence of carbon dioxide enhance product distribution to yield a higher diesel fraction (C13 to C15), when compared to results without carbon dioxide as a medium, which favor gasoline fraction (C7 to C9). The findings also illustrate that operating in the supercritical region enhances product distribution, but depending on the solvent density, could potentially produce large amounts of oxygenates (alcohols, ketones) in the product distribution.

This paper presents the culmination of an investigation on carbon nanotubes as catalysts for the hydrogenation of carbon monoxide. Carbon nanotubes (CNTs) have been found to have extraordinary physical properties and the potential for use in a variety of applications. They have been utilized as catalyst supports in many reactions, including the conversion of syngas to ethanol. The specific role played by CNTs in these reactions, aside from that of a support structure, has not been evaluated, however. Presented here are parametric studies on Fischer-Tropsch Synthesis with carbon nanotubes as active catalysts. The use of as-produced CNTs (containing trace amounts of iron from the synthesis process) resulted in a 100-fold increase in carbon monoxide conversion per unit mass of catalyst over a traditional Fe-Zn-K/γ-alumina catalyst. This value (CO conversion per unit mass of catalyst) was raised to nearly 1500 times as high as for Fe-Zn-K/γ-alumina when purified CNTs were used in the same FT synthesis. Because iron is a primary catalyst in the FT synthesis, it can be argued that the iron in the CNTs was responsible for the catalytic behavior. However, the iron content in the MWNTs (0.014 g, ≈ 5 mass%) and SWNTs (0.04 g, ≈ 27 mass%) compared to that of the traditional iron-loaded alumina support (2.5 g, ≈ 12.5 mass%), strongly suggests that iron alone cannot be responsible for the catalysis. Although single-walled nanotube (SWNT) catalysts provided high CO conversion, methane represented the bulk of the products. Conversely, multi-walled nanotubes (MWNTs) produced mostly liquid hydrocarbons and oxygenates, indicating that the CNT structure is an important factor in the hydrogenation of CO. The parametric experiments show that temperature, pressure and the syngas composition all play key roles in the distribution of liquid products. In general, an increase in temperature correlated to an increase in hydrocarbon chain length and the formation of more alcohols; above a certain temperature, the distribution shifted to 100% alcohols. Likewise, lower pressures resulted in hydrocarbons of shorter carbon chain length and at higher pressures, more alcohols were formed. Studies were also conducted on the effect of syngas composition and the effect of different types of CNTs. Syngas with 1:1 ratio (H2:CO) produced longer hydrocarbon chains than those produced by 3:1 syngas. The type of CNTs used in FT also affected the products but no clear relationships could be discerned.

Mediante el proceso Fischer-Tropsch es posible obtener, a partir del carbón, hidrocarburos que pueden ser utilizados como combustible. Como veremos más adelante,esta fue la razón del rápido desarrollo de este proceso.Los compuestos carbénicos son estudiados en los laboratorios de la SecciónQuímica de la Pontificia Universidad Católica del Perú, y siendo el procesoFischer-Tropsch el ejemplo de catálisis , heterogénea por excelencia,resulta interesante conocer su relación.El presente artículo es una pequeña introducción a la síntesis FischerTropsch. Debido a la complejidad y al gran número de puntos involucrados, tocaremos sólo los puntos más importantes con el fin de captar el interés sobre un tema que puede ser de importancia para el desarrollo del Perú.

The new series of μ(α, ω)-alkanediyl compounds of ruthenium, [CpRu(CO)₂]₂[μ-(CH₂)ₙ], where n=5-10, have been prepared from Na[CpRu(CO)₂] and the corresponding diiodoalkane. These compounds, which are stable crystalline solids at ambient temperature, have been fully characterised by microanalysis, infrared, ¹H and ¹³C NMR spectroscopy, melting point and mass spectrometry. The new heterodinuclear complex [Cp(CO)₂Fe(CH₂)₄Ru(CO)₂Cp] has been synthesised by the reaction of [CpFe(CO)₂(CH₂)₄I] with Na[CpRu(CO)₂] and characterised by all the above mentioned techniques.

A descoberta de uma nova província petrolífera, conhecida como pré-sal, localizada no litoral brasileiro, representa um novo marco na produção de petróleo mundial. Dentre os vários desafios encontrados para exploração e produção dessa região, a presença de CO2 em grandes concentrações nos fluidos de alguns desses reservatórios tem sido um dos desafios de maior relevância para as empresas que exploram e produzem nessa área (FORMIGLI, 2007). Uma forma alternativa de sequestro do CO2 retirado do gás natural é a sua utilização como matéria prima ou co-alimentação para a síntese de produtos químicos, em especial aqueles com grande demanda de mercado. Um dos produtos que podem ser obtidos indiretamente a partir do CO2 é o petróleo sintético, produzido pelo processo conhecido como Gas-to-Liquids, ou GTL. Neste trabalho foi analisada a viabilidade técnica, econômica e potencial de captura de CO2, da produção de petróleo sintético, pelo processo GTL, offshore, a partir de dióxido de carbono (CO2) e metano (CH4), presentes na corrente de rejeito do tratamento do gás processado em uma plataforma de produção de petróleo e gás, através das reformas seca e a vapor, seguida da síntese Fischer-Tropsch. A partir de dados de literatura e com uso de simulador comercial de processos, a simulação do processo foi desenvolvida e diferentes alternativas para reaproveitamento das correntes residuais do processo foram analisadas, incluindo o reciclo e a queima dos efluentes combustíveis, assim como foram aplicadas técnicas de integração energética, otimização e análise econômica de processos. Os resultados indicaram que o processo, mássica e energeticamente integrado, na condição de menor emissão de CO2 e maior retorno financeiro, produziu petróleo sintético de forma técnica e economicamente viável. Os resultados indicaram ainda que o processo GTL, com as tecnologias utilizadas, não é indicado como método de captura de CO2 devido o fato de a geração desse componente para a produção de petróleo sintético ser duas vezes maior que a quantidade alimentada. / The discovery of a new oil province known as pre-salt, located in the Brazilian coast, represents a new frontier in the world\'s oil production. Among other challenges involved in the exploration and production in that region, the CO2 concentration at high levels in the fluids of some of those reservoirs has been the most relevant challenge for the companies that explore and produce in that area (FORMIGLI, 2007). An alternative to sequestering the CO2 extracted from natural gas is using it as a supply of raw material or as an input to the synthesis of chemical products, especially those with great market demand. One of the products that can be obtained indirectly from CO2 is synthetic fuel, produced by the process known as Gas-to- Liquids, or GTL. In this work the technical, economical and potential feasibility of CO2 capture is analyzed, as well as the production of synthetic fuel using the GTL process, offshore, from carbon dioxide (CO2) and methane (CH4), found in the waste chain of the gas treatment in an oil and gas production platform, through dry and steam reforming, followed by Fischer-Tropsch synthesis. Thus, based on literature data and on the use of a commercial process simulator, the simulation of the suggested process was developed and different alternatives to the reutilization of the waste chains were analyzed, including the recycling and burning of some effluent streams. Techniques of energetic integration, optimization and economic analysis of process have also been applied. The results indicated that the process, mass and energy integrated in the condition of lower CO2 emissions and greater financial return, produced synthetic oil in a technically and economically feasible way. The results also indicated that the GTL process, with the technologies used, is not suitable as a method for CO2 capture due to the fact that the generation of this component for the production of synthetic oil is two times greater than the amount fed.

A descoberta de uma nova província petrolífera, conhecida como pré-sal, localizada no litoral brasileiro, representa um novo marco na produção de petróleo mundial. Dentre os vários desafios encontrados para exploração e produção dessa região, a presença de CO2 em grandes concentrações nos fluidos de alguns desses reservatórios tem sido um dos desafios de maior relevância para as empresas que exploram e produzem nessa área (FORMIGLI, 2007). Uma forma alternativa de sequestro do CO2 retirado do gás natural é a sua utilização como matéria prima ou co-alimentação para a síntese de produtos químicos, em especial aqueles com grande demanda de mercado. Um dos produtos que podem ser obtidos indiretamente a partir do CO2 é o petróleo sintético, produzido pelo processo conhecido como Gas-to-Liquids, ou GTL. Neste trabalho foi analisada a viabilidade técnica, econômica e potencial de captura de CO2, da produção de petróleo sintético, pelo processo GTL, offshore, a partir de dióxido de carbono (CO2) e metano (CH4), presentes na corrente de rejeito do tratamento do gás processado em uma plataforma de produção de petróleo e gás, através das reformas seca e a vapor, seguida da síntese Fischer-Tropsch. A partir de dados de literatura e com uso de simulador comercial de processos, a simulação do processo foi desenvolvida e diferentes alternativas para reaproveitamento das correntes residuais do processo foram analisadas, incluindo o reciclo e a queima dos efluentes combustíveis, assim como foram aplicadas técnicas de integração energética, otimização e análise econômica de processos. Os resultados indicaram que o processo, mássica e energeticamente integrado, na condição de menor emissão de CO2 e maior retorno financeiro, produziu petróleo sintético de forma técnica e economicamente viável. Os resultados indicaram ainda que o processo GTL, com as tecnologias utilizadas, não é indicado como método de captura de CO2 devido o fato de a geração desse componente para a produção de petróleo sintético ser duas vezes maior que a quantidade alimentada. / The discovery of a new oil province known as pre-salt, located in the Brazilian coast, represents a new frontier in the world\'s oil production. Among other challenges involved in the exploration and production in that region, the CO2 concentration at high levels in the fluids of some of those reservoirs has been the most relevant challenge for the companies that explore and produce in that area (FORMIGLI, 2007). An alternative to sequestering the CO2 extracted from natural gas is using it as a supply of raw material or as an input to the synthesis of chemical products, especially those with great market demand. One of the products that can be obtained indirectly from CO2 is synthetic fuel, produced by the process known as Gas-to- Liquids, or GTL. In this work the technical, economical and potential feasibility of CO2 capture is analyzed, as well as the production of synthetic fuel using the GTL process, offshore, from carbon dioxide (CO2) and methane (CH4), found in the waste chain of the gas treatment in an oil and gas production platform, through dry and steam reforming, followed by Fischer-Tropsch synthesis. Thus, based on literature data and on the use of a commercial process simulator, the simulation of the suggested process was developed and different alternatives to the reutilization of the waste chains were analyzed, including the recycling and burning of some effluent streams. Techniques of energetic integration, optimization and economic analysis of process have also been applied. The results indicated that the process, mass and energy integrated in the condition of lower CO2 emissions and greater financial return, produced synthetic oil in a technically and economically feasible way. The results also indicated that the GTL process, with the technologies used, is not suitable as a method for CO2 capture due to the fact that the generation of this component for the production of synthetic oil is two times greater than the amount fed.

A thesis submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2016. / The production of liquid transportation fuels and chemicals by the Fischer-Tropsch (FT) synthesis continues to garner attention due to its economic and environmental benefits. This interest is also compounded by the flexibility to use readily available materials as feedstocks for synthesis gas production, with coal, natural gas, biomass and recently shale gas being used. Although this process is over 90 years old, challenges still remain. In this study, we have attempted to understand several FT synthesis challenges by exploring the use of carbon spheres as a model support for Co, Fe and Fe-Co FT catalysts. Thus the synthesis, characterization and application of carbon spheres with distinct architectures are described. The synthesis of solid carbon spheres using a sucrose precursor yielded materials that were mono-dispersed (600 nm) and adopted a necklace-like accreted conformation. Upon further investigation, it was demonstrated that annealing is useful for tuning the properties of the as-prepared materials to have high surface areas (> 500 m2/g), good thermal stability (>660 °C) and a mesoporous (> 2 nm) pore structure. Deposition of a Fe-Co bimetallic catalyst yielded oxides of the monometallic species with relatively small crystallites, with sizes in the range 7.9 – 14.4 nm. Reduction of the bimetallic samples was monitored by using in situ PXRD and TPR techniques, which revealed that a Co-Fe type-alloy is one of the phases formed on Co-rich samples at T > 450 °C. Interestingly, high relative abundances of this alloy did not correlate with high C5+ selectivities in Fischer-Tropsch synthesis; instead Co-rich/Fe-poor catalysts gave the best selectivity. The effect of the support morphology in heterogeneous catalysis was investigated by using high surface area solid and hollow carbon spheres (>560 m2/g) prepared from a resorcinol-formaldehyde precursor as support material. Loading the Co and Fe precursors on these two supports was shown by TEM and PXRD to result in smaller and well dispersed metal particles on the hollow support material. This corresponded with high activities and C5+ selectivities for the Co and Fe catalysts supported on the hollow carbon spheres. TEM studies revealed that the Co and Fe particles tended to sinter significantly when dispersed on a material with a solid architecture. iv Post-synthesis N-doping using a melamine precursor was shown by XPS to incorporate high quantities of nitrogen (up to 13%) on to the surface of the 30 nm thick shells of the hollow carbon spheres. On further investigation, N-doping by this method was shown to have minimal effects on the thermal stability and crystallinity of the materials. The N-doped HCSs were shown to be good anchors of Co particles as displayed by the good dispersion, activity and minimal sintering tendency of catalysts supported on N-doped HCSs. Studies conducted herein have demonstrated the versatility of carbon spheres as a model support, and how their properties can be tailored to suit the desired specifications by simply adjusting the synthesis parameters. We have also highlighted how the chemical inertness of these materials allows for studies on metal-metal interactions at elevated temperatures for bimetallic catalyst systems. The monodisperse, morphology-tunable aspects of carbon spheres were particularly useful in modelling the effect of the support morphology in Fischer-Tropsch synthesis. It is believed that the versatility of CSs demonstrated in this study can also be exploited in other heterogeneous catalytic systems. / LG2017

School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa August, 2016 / One gram amounts of a commercial iron based catalyst were loaded into three reactors and reduced with syngas, hydrogen and carbon monoxide respectively. Fischer Tropsch experiments on the three reactors in parallel with the same operating conditions, namely 60 mL(NTP)/min, 1 bar gauge and 250 °C, were then conducted for extended periods and the gaseous products analysed. Initially (for about 150 hours) the three catalysts had quite different carbon monoxide conversions. After this until about 1000 hours the conversions were similar. However the distribution of products for the differently reduced catalyst was significantly different. This suggested that permanent changes had been done to the catalysts by the different reducing conditions. To try to understand what the differences during the reduction process might be, a thermodynamic analysis of the solid phases after reduction was done. Unfortunately because all the thermodynamic data for the possible carbides was not available this analysis was of limited value. However it did suggest that hydrogen reduced catalyst might contain more oxides and the carbon monoxide reduced catalyst might contain more carbides. Some electron microscope and XRD experiments supported these ideas and might account for the different selectivities of the differently reduced catalysts. Runs after about 5000 hours were done at different flowrates (60, 30 and 15 mL(NTP)/min) of syngas and again the big effects were on differences between the selectivities, the big effects being when going to the lowest flowrate. After about 12000 hours regeneration of the catalysts was then done by oxidation and then the same syngas reduction on all the catalysts. Runs were then done at different pressures (1, 10 and 20 bar gauge) and again selectivities were the biggest effects that remained, clearly showing the initial reduction had made permanent changes. In the final section some novel plots were used to try to make more sense of the results. It was shown that for all the catalysts the Olefin to Paraffin ratios were tied to each other under all conditions and that they were mainly a function of the conversions with much higher values at low conversions. / MT2017

PhD, Faculty of Engineering and the Built Environment, University of the Witwatersrand / Fischer-Tropsch is a process that converts synthesis gas (especially H2 and CO) into hydrocarbons by the mean of metal catalysts (such as Fe, Co, Ru, and Ni). Its success depends strongly on the catalyst used for the reaction, the reactor where the reaction is taking place, and some parameters such as the operating temperature, the reactor pressure, and the gas purity, composition (ratio H2:CO) and flow rate. Besides the above parameters, other factors, such as the degree of reduction of the catalyst, also play an important role for a successful FT reaction. Water can deactivate (by re-oxidation) the catalyst and carbon deposit can reduce the catalyst’s activity. It is well known that FT is a complex reaction because of the range of products that it produces as well as the reactions that occur during the process. A good choice or combination of catalysts, reactor and operating conditions can help to control the product spectrum. 2 In this thesis we develop a simple graphical technique to represent the mass, energy balance and thermodynamic constraints that affect both the catalyst and the reactor. This graphic model is shown to be capable of opening up insights into reactor operations and indicating preferred operational regions. The diagrams make it possible to visualize operations and understand the interactions between the catalysts and the reactor. The mass and energy balances also provide information about the best possible region in which the FT reactor system can be designed and operated. A few catalysts (Fe/TiO2, Co/TiO2 and Fe:Co/TiO2) were prepared for the completion of this work. Some of them were tested separately and others were mixed in the same reactor. The results showed that the physical mixture (of Fe/TiO2 and Co/TiO2) and bimetallic catalysts behave differently from one another. The addition of Fe Fe/TiO2 to a constant amount of Co/TiO2 results in an increase of CO hydrogenation activity, WGS activity and CH4 selectivity. However, the position of the two catalysts in the reactor (one followed by another) shows little effect on the rate of hydrogenation of CO and the CO conversion.