The Fischer-Tropsch Synthesis in the Liquid Phase

Kölbel, Herbert; Rálek, M.

doi:10.1080/03602458008067534

Cited by 244 publications

(104 citation statements)

References 30 publications

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“…Instead, the hydrogen is synthesized in situ by a water gas shift reaction (CO þ H 2 O ! CO 2 þ H 2 ) [27]. Under optimal laboratory conditions, the reaction proceeds with more than 80 per cent CO conversion.…”

Section: A Linked Source Of Phosphate and Lipids: Towards A Higher Ormentioning

confidence: 97%

“…Straight chain alkanols, ketones, aldehydes (including H 2 CO) and carboxylic acids are formed in addition to straight chain hydrocarbons [27]. This array of products is produced in the temperature range 180 -2808C; at higher temperatures, CO conversions drop slowly but methane production becomes predominant (methanation).…”

Section: A Linked Source Of Phosphate and Lipids: Towards A Higher Ormentioning

confidence: 99%

“…Under optimal laboratory conditions, the reaction proceeds with more than 80 per cent CO conversion. Hydrocarbon yields in the KE reaction are optimal when the CO : H 2 O ratio is ca 2.6-an excess of CO leads to carbon deposition, whereas an excess of H 2 O causes catalyst oxidation with concomitant production of H 2 [27]. In the presence of a large amount of iron, these stoichiometric processes would be expected to shift the local CO : H 2 O ratio towards the optimal for hydrocarbon synthesis.…”

Section: A Linked Source Of Phosphate and Lipids: Towards A Higher Ormentioning

confidence: 99%

“…Short chain alkanols tend to predominate over medium and long chain alkanols in the oxygenate fraction of products synthesized by the KE variant of the FT reaction [27], and so, as a representative KE oxygenate fraction for phosphorylation, we employed a mixture of ethanol, hexanol and decanol, with the C 2 alkanol in a large molar excess over the longer chain species. Because ethyl phosphate is not amphiphilic, significant chemoselectivity would have to operate for membrane-forming amphiphiles to be produced by phosphorylation of such a mixture using sub-stoichiometric phosphate.…”

Section: Alkanol Phosphorylationmentioning

confidence: 99%

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Prebiotic chemistry: a new modus operandi

Powner

Sutherland

2011

Phil. Trans. R. Soc. B

124

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A variety of macromolecules and small molecules-(oligo)nucleotides, proteins, lipids and metabolites-are collectively considered essential to early life. However, previous schemes for the origin of life-e.g. the 'RNA world' hypothesis-have tended to assume the initial emergence of life based on one such molecular class followed by the sequential addition of the others, rather than the emergence of life based on a mixture of all the classes of molecules. This view is in part due to the perceived implausibility of multi-component reaction chemistry producing such a mixture. The concept of systems chemistry challenges such preconceptions by suggesting the possibility of molecular synergism in complex mixtures. If a systems chemistry method to make mixtures of all the classes of molecules considered essential for early life were to be discovered, the significant conceptual difficulties associated with pure RNA, protein, lipid or metabolism 'worlds' would be alleviated. Knowledge of the geochemical conditions conducive to the chemical origins of life is crucial, but cannot be inferred from a planetary sciences approach alone. Instead, insights from the organic reactivity of analytically accessible chemical subsystems can inform the search for the relevant geochemical conditions. If the common set of conditions under which these subsystems work productively, and compatibly, matches plausible geochemistry, an origins of life scenario can be inferred. Using chemical clues from multiple subsystems in this way is akin to triangulation, and constitutes a novel approach to discover the circumstances surrounding the transition from chemistry to biology. Here, we exemplify this strategy by finding common conditions under which chemical subsystems generate nucleotides and lipids in a compatible and potentially synergistic way. The conditions hint at a post-meteoritic impact origin of life scenario.

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Section: A Linked Source Of Phosphate and Lipids: Towards A Higher Ormentioning

confidence: 97%

Section: A Linked Source Of Phosphate and Lipids: Towards A Higher Ormentioning

confidence: 99%

Section: A Linked Source Of Phosphate and Lipids: Towards A Higher Ormentioning

confidence: 99%

Section: Alkanol Phosphorylationmentioning

confidence: 99%

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Prebiotic chemistry: a new modus operandi

Powner

Sutherland

2011

Phil. Trans. R. Soc. B

124

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“…1,2 Potassium also increases the olefin content and the molecular weight of FTS products. 26 The evolution of the Fe near-edge spectral features in Fe and Fe-K-Cu oxide precursors during exposure to synthesis gas was used in order to examine the effects of H 2 in modifying the structural details detected during carburization in CO, as well as the role of the K and Cu on the rate and products of the transformation that occurs during the initial exposure of these oxide precursors to synthesis gas. Figure 5 shows the near-edge spectra for Fe, Fe-Cu, Fe-K, and Fe-K-Cu oxide precursors measured in situ after contact with synthesis gas at 523 K for 5 h. The absorption edge energy was lower and the spectra resembled the Fe carbide spectrum (Figure 2) more closely when K or Cu was present in the sample.…”

Section: In Situ X-ray Absorption Spectra Of Fe-k-cu Oxide Precursorsmentioning

confidence: 99%

Structure and Site Evolution of Iron Oxide Catalyst Precursors during the Fischer−Tropsch Synthesis

2001

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The contacting of Fe oxide precursors with synthesis gas (H 2 /CO mixtures) leads to structural and chemical changes and to the formation of the active sites required for the Fischer-Tropsch synthesis (FTS). The local structure and oxidation state of the starting Fe 2 O 3 precursors promoted by Cu and/or K were probed using in situ X-ray absorption spectroscopy during these processes. The activation of these precursors occurs via reduction to Fe 3 O 4 followed by carburization to form FeC x . FTS reaction rates increased markedly during the initial stages of carburization, suggesting that the conversion of near-surface layers of Fe 3 O 4 to FeC x is sufficient for the formation of the required active sites. Thus, bulk structural probes, and any ex situ techniques without concurrent measurements of the products evolved during activation and FTS, can lead to misleading structurefunction relations. The initial rate of carburization and the extent of carburization and the FTS rate at steadystate were higher for Fe 2 O 3 precursors containing either Cu or K. These effects were stronger when both promoters were present. K and Cu provide CO and H 2 activation sites, which lead to the nucleation of multiple carbide regions on Fe oxide surfaces. The larger number of nucleation sites leads to higher initial carburization rates and to smaller FeC x crystallites. These smaller crystallites, in turn, provide higher active surface areas, shorter bulk diffusion distances, more complete carburization of Fe 2 O 3 precursors, and higher steady-state FTS rates. These effects of K and Cu on the number of available FeC x sites were confirmed by titrating surface sites using CO after FTS reactions. It appears that K and Cu act predominantly as structural promoters, which increase the surface area of the active FeC x phases. Chemical promotion of catalytic rates by these additives appears not to be required to explain the observed FTS rate enhancements in the presence of K or Cu. These structural promotion effects of Cu and K account for the apparent but non-causal correlation between bulk FeC x contents and FTS rates at steady-state, even though the carburization of only near-surface regions in bulk Fe 3 O 4 is sufficient to achieve steady-state FTS turnover rates.

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