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" Kobalt yüzeylerindeki kükürtün fischer tropsch sentezinin temel raksiyonlarına etkisi "
Dağa, Yağmur
Kızılkaya, Ali Can
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Latin Dissertation
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| Language of Document
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English
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| Record Number
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1112210
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| Doc. No
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TLpq2522814570
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| Main Entry
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Dağa, Yağmur
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Kızılkaya, Ali Can
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| Title & Author
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Kobalt yüzeylerindeki kükürtün fischer tropsch sentezinin temel raksiyonlarına etkisi\ Dağa, YağmurKızılkaya, Ali Can
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| College
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Izmir Institute of Technology (Turkey)
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| Date
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2020
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| student score
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2020
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| Degree
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Master's
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| Page No
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103
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| Abstract
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Industrial observations indicate that sulfur acts a poison for Fischer-Tropsch Synthesis (FTS) and surface science studies show that sulfur blocks the adsorption sites for reactants on cobalt surfaces. However, various experimental studies have indicated conflicting results about the effect of sulfur on cobalt FTS catalyst activity and selectivity. This study aims to clarify the effect of sulfur on cobalt FTS catalysts by molecular modelling of the elementary reactions of FTS on surfaces that are present on sulfur covered cobalt surfaces that are present in fcc-Co nanoparticles, using Density Functional Theory (DFT). For 0.25 ML sulfur coverage, it is found that on bare, C and O covered surfaces, S is the main dissociation product, while HS can be present on low coverages. Atomic sulfur decreases the adsorption energies of all species investigated, while the decrease is more pronounced for CO compared to H2. The effect of S on the elementary FTS reactions direct and H-assisted CO dissociation, carbon hydrogenation, carbon coupling and oxygen removal are also investigated. The results indicate that S inhibits mainly the oxygen removal reaction, in terms of both H2O and CO2. CO dissociation is not inhibited but rather slowed down, due to increasing activation barriers. It is also found that carbon hydrogenation barriers are significantly decreased, while carbon coupling barriers are unaffected. These results indicate that the intrinsic effect of sulfur poisoning would be to increase methane selectivity, while decreasing the selectivity to long chain hydrocarbons.
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Catalysis
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Chemical engineering
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Fischer-Tropsch process
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