Synthesis of Nanostructured Silica for Use as a Support for Iron Fischer-Tropsch Catalysts PDF Download
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Author: Keneiloe Khoabane
Publisher:
ISBN:
Category : Synthesis
Languages : en
Pages : 500
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Author: Keneiloe Khoabane
Publisher:
ISBN:
Category : Synthesis
Languages : en
Pages : 500
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Author: Abdulbaset M. Alayat
Publisher:
ISBN: 9780438393004
Category : Biomass energy
Languages : en
Pages : 324
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This dissertation presents findings on the preparation and characterization of silica nanosprings (NS) supported Fe and Co catalysts for Fischer-Tropsch (FT) reactions. Silica NS with a high surface area of 400 m2/g were chosen as a new 1-dimensional nanostructured support for Fe and Co based FT catalysts and divided into three sections. Section 1 involved the preparation and characterization of Co/NS catalysts as well as to examine the effects of two different reduction temperatures on the FT catalytic performance of this Co/NS catalyst. The prepared Co/NS catalysts were characterized before the FT reaction by various analytical techniques such as surface area, X-ray diffraction, transmission electron microscopy , energy dispersive X-ray spectroscopy, temperature programmed reduction (CO and H2), X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy and thermogravimetric analysis. The activity and selectivity of all catalysts were evaluated in a quartz fixed bed micro-reactor (H2/CO of 2:1, 230-270 °C). The effect of reaction temperature on the catalytic performance of Co/NS catalyst was studied. The results showed that the catalyst reduced at a temperature of 609 °C had higher production rate of C6-C17 hydrocarbons than the catalyst reduced at 409 °C. It also was found that the Co/NS catalyst resulted in more stability compared to with conventional catalysts. Section 2 examined the effect of three preparation techniques (impregnation, precipitation and 2-step sol-gel) and activation conditions (H2, CO or H2+CO) on catalytic performance of these Fe/NS catalysts. It was found that the Fe/NS catalyst prepared by impregnation technique and activated with CO displayed the highest CO conversion (76.6%) and a wide distribution of light hydrocarbon (C6 to C14). Moreover, the XRD and XPS results of Fe/NS catalysts showed three different Fe crystalline phases with different particle sizes. Section 3 examined the addition of Ru, Mo, Co and Cu as promoters on the Fe/NS catalysts. It was found that the promotion of the Fe catalyst supported on NS with Ru, Mo, Co and Cu increased the CO conversion, shifted the FTS product distributions and improved the selectivity towards C6-C16 olefins instead of aromatics in unpromoted Fe/NS catalyst. New types of Co and Fe catalysts were synthetized using silica nanosprings (NS) as a new 1-dimensional nanostructured support, and used in the Fischer-Tropsch synthesis. By using these catalysts, good activity, selectivity to C6-C16 hydrocarbons (liquid fuels) and catalytic stability have been achieved. Furthermore, the incorporation of promoters, such as Ru, Mo, Co and Cu, into these catalysts can have effect leading to both high conversion and selectivity.
Author: Eshan Ben Yeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 254
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Author: Jeffrey Allen Amelse
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Jian Xu
Publisher:
ISBN:
Category : Fischer-Tropsch process
Languages : en
Pages : 171
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Author: Nicole S. Hondow
Publisher:
ISBN:
Category : Catalysts
Languages : en
Pages : 484
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Transition metals have been extensively studied as catalysts, and certain metals are known to be highly selective and active for certain processes. It is possible to use metal clusters as models for reactions occurring at metal surfaces, but it is often found that in practical applications these complexes are unstable and break down. It is possible to support or stabilise a metal species on, or in, an inorganic framework, making heterogeneous catalysts. A study of metal cluster chemistry with mixed-donor phosphine ligands was conducted, with several new ruthenium complexes synthesised. The chemistry of metal-sulfur interactions is applicable to the removal of sulfur from crude oil, and in an investigation to this chemistry, the bifunctional ligand HSCH2CH2PPhH was added to ruthenium clusters (Chapter 2). The addition of this sulfur-phosphine ligand to the cluster [Ru3([mu]-dppm)(CO)10] produced the carbonyl substituted cluster [Ru3([mu]-dppm)(H)(CO)7(SCH2CH2PPhH)] and the bridged complex [Ru3([mu]-dppm)(H)(CO)8(SCH2CH2PPhH)Ru3([mu]-dppm)(CO)9], as well as recovery of the starting material. Further reactions with this ligand were examined with [Ru3(CO)12] and other complexes were synthesised with different clusters and ligands (Chapter 2). The M41S materials, MCM-41 and MCM-48, are well ordered porous materials with high surface areas (Chapter 3). The incorporation of three different types of metal species, metallosurfactants, metal clusters and nanoparticles, into these materials was examined in an attempt to make heterogeneous catalysts for the Fischer-Tropsch process. The success of this was studied using characterisation techniques such as powder X-ray diffraction, transmission electron microscopy and BET surface area measurements. Metallosurfactants containing either copper or cobalt were added directly to the synthesis of the porous materials in an attempt to incorporate the metals into the framework structure of the porous silica (Chapter 3). This resulted in well ordered iv porous materials, but the successful incorporation of the metal species was found to be dependent on several factors. Organometallic clusters containing metals such as copper, iron and ruthenium, with supporting carbonyl ligands, were added post-synthesis to MCM-41 and MCM-48 (Chapter 4). Various reaction conditions were examined in attempts to ensure small particle formation. The optimum incorporation of nanoparticles containing iron and platinum was found to occur when a suspension of pre-made and purified nanoparticles was added post-synthesis to the M41S materials (Chapter 4). These materials resulted in porous silicas with well dispersed, small metal particles. The optimum conditions for the calcination of these new materials were determined, in an attempt to remove the ligands and stabilisers and retain the small metal particle size (Chapter 5). Testing for the Fischer-Tropsch process was conducted in a fixed bed reactor through which a flow of synthesis gas containing carbon monoxide and hydrogen could pass over the material (Chapter 5). Analysis by gas chromatography showed that the major product produced by all materials tested was methane, but other hydrocarbons were produced in small amounts, including hexane.
Author: Phylander Omosigho Atubi
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Author: Joffrey Huve
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Fischer-Tropsch synthesis (FTS) is gaining renewed interests as it allows converting alternative feedstocks (biomass) into liquid fuels. Compared to Co-based catalysts, state of the art Fe catalysts show lower activity, faster deactivation and lower selectivity as it produces an undesirable amount of CO2. Despite decades of studies, the origins of low activity and selectivity and fast deactivation are still unclear. Typical Fe based catalysts are highly metal loaded (>70 wt.%) and composed of many different phases, which strongly impedes the establishment of structure-activity relationships. There is a need to develop more active, more selective and more stable iron FTS catalysts by rational approaches.The synthesis of well-controlled 3.5 nm iron nanoparticles encapsulated in the walls of a hollow-silicalite-1 zeolite (Fe@hollow-silicalite-1) is presented. The encapsulation prevents particle sintering under FTS conditions leading to a high and stable Fe dispersion. The catalyst Fe@hollow-silicalite-1 is active and highly selective in FTS. Most importantly, Fe@hollow-silicalite-1 does not produce CO2 in contrast to all other Fe-based catalysts. The strong hydrophobicity of the silicalite-1 is likely the origin of the lack of CO2 production by inhibition of the forward WGS reaction. We demonstrated that Fe@hollow-silicalite-1converts CO2 into CO by the reverse WGS reaction. In order to establish a structure-activity relationship, a series of Fe-based catalysts with well-controlled particle sizes were synthesized and characterized (TEM, in-situ XANES, in-situ Mössbauer, XRD). We observed two distinct categories of TOFs depending on the particle size, ~10-2 s-1 for larger (>20 nm) and ~10-3 s-1 for smaller ones.
Author: Peter M. Maitlis
Publisher: John Wiley & Sons
ISBN: 3527656855
Category : Science
Languages : en
Pages : 404
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Greener Fischer-Tropsch Processes How can we use our carbon-based resources in the most responsible manner? How can we most efficiently transform natural gas, coal, or biomass into diesel, jet fuel or gasoline to drive our machines? The Big Questions today are energy-related, and the Fischer-Tropsch process provides industrially tested solutions. This book offers a comprehensive and up-to-date overview of the Fischer-Tropsch process, from the basic science and engineering to commercial issues. It covers industrial, economic, environmental, and fundamental aspects, with a specific focus on “green” concepts such as sustainability, process improvement, waste-reduction, and environmental care. The result is a practical reference for researchers, engineers, and financial analysts working in the energy sector, who are interested in carbon conversion, fuel processing or synthetic fuel technologies. It is also an ideal introductory book on the Fischer-Tropsch process for graduate courses in chemistry and chemical engineering.
Author: Thongthai Witoon
Publisher:
ISBN:
Category : Catalysts
Languages : en
Pages : 222
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