Synchrotron Radiation and Oil Industry Research

Lynch, John P.

doi:10.2516/ogst:2005052

Cited by 4 publications

(6 citation statements)

References 58 publications

(58 reference statements)

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“…At the Co edge, a single shell of six oxygens surrounding the central cobalt at 2.06 Å can be identified. The XANES profile shows a resemblance to those of cobalt silicates …”

Section: Discussionmentioning

confidence: 90%

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X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

et al. 2007

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X-ray absorption fine structure (EXAFS) and X-ray absorption near-edge structure (XANES) techniques at both Fe and Co K-edges were used to investigate the formation of CoFe 2 O 4 nanoparticles embedded in a silica aerogel matrix as a function of calcination temperature and CoFe 2 O 4 content. In particular, nanocomposite aerogels containing relative CoFe 2 O 4 amounts of 5 and 10 wt % and calcined at 450, 750, and 900°C were studied. The evolution of the nanophase with calcination temperatures depends on the composition. In the sample containing 10 wt % of nanophase, results indicate that CoFe 2 O 4 nanocrystals were formed after calcination at 750°C, whereas in the sample containing 5 wt % of nanophase, they were obtained only after calcination at 900°C. Quantitative determination of the distribution of the iron and cobalt phase in the octahedral and tetrahedral sites of the spinel structure shows that cobalt ferrite prepared by sol-gel has a partially inverted spinel structure with a degree of inversion around 0.70.

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“…At the Co edge, a single shell of six oxygens surrounding the central cobalt at 2.06 Å can be identified. The XANES profile shows a resemblance to those of cobalt silicates …”

Section: Discussionmentioning

confidence: 90%

“…The XANES profile shows a resemblance to those of cobalt silicates. 44 The calcination at 750 °C gives rise in the A10 samples to the beginning of the formation of cobalt ferrite that coexists with the phases present at 450 °C. In the A5 samples, the formation of cobalt ferrite before calcination at 900 °C is not completely evident.…”

Section: Discussionmentioning

confidence: 99%

X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

et al. 2007

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“…XAS has been extensively used for identification of the type of neighboring atoms, measuring interatomic distances, and evaluation of coordination number and structural and thermal disorder. The rapid expansion of XAS is due to the growing availability of synchrotron radiation . XAS incorporates the XANES and EXAFS techniques.…”

Section: 4 X-ray Absorption Spectroscopy (Xanes and Exafs)mentioning

confidence: 99%

Advances in the Development of Novel Cobalt Fischer−Tropsch Catalysts for Synthesis of Long-Chain Hydrocarbons and Clean Fuels

2007

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Currently, there are two FT operating modes: [11][12][13] highand low-temperature FT processes (Figure 1). In the hightemperature FT (573-623 K, HTFT) process 14 syngas reacts in a fluidized bed reactor in the presence of iron-based catalyst to yield hydrocarbons in the C1-C15 hydrocarbon range. This process is primarily used to produce liquid fuels, although a number of valuable chemicals, e.g., R-olefins, can be extracted from the crude synthetic oil. Oxygenates in the aqueous stream are separated and purified to produce alcohols, acetic acid, and ketones including acetone, methyl ethyl ketone, and methyl isobutyl ketone.Both iron and cobalt (Fe, Co) catalysts can be used in the low-temperature FT (473-513 K, LTFT) process 8,10 (Figure 1) for synthesis of linear long-chain hydrocarbon waxes and paraffins. High-quality sulfur-free diesel fuels are produced in this process. Most of the FT technologies developed in last two decades are based on the LTFT process. These new LTFT processes have involved syngas with a high H 2 /CO ratio, which is generated by vaporeforming, autothermal reforming, or partial oxidation using natural gas as a feedstock.Because of their stability, higher per pass conversion, 8 and high hydrocarbon productivity, cobalt catalysts represent the optimal choice for synthesis of long-chain hydrocarbons in the LTFT process.

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“…Several spectroscopic methods such as X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and X-ray absorption (XANES/EXAFS) [103] also allow the measurement of the extent of reduction. The accuracy in measuring the extent of reduction depends, however, on the quality of the decomposition of spectra, which often represent a combination of signals coming from different reduced and oxidized phases.…”

Section: Comparison Of Magnetic Methods and Other Techniques Of Catalmentioning

confidence: 99%

“…XPS is only sensitive to the surface and subsurface layers of the catalyst [110] and non-uniform distribution of active components with the catalyst grain can significantly affect the results of XPS analysis. EXAFS provides [103,106] information about the sizes of metal particles smaller than 1-2 nm. For larger particles, however, the accuracy of this technique is much smaller due to very minor correlation between particle size and coordination number [111].…”

Section: Comparison Of Magnetic Methods and Other Techniques Of Catalmentioning

confidence: 99%

F ischer‐ T ropsch Process

2006

Van Nostrand's Scientific Encyclopedia

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Résumé -La caractérisation par la méthode magnétique des catalyseurs Fischer-TropschCet article passe en revue les développements récents dans le domaine de la caractérisation des catalyseurs Fischer-Tropsch à base de cobalt, de fer et de nickel par la méthode magnétique. La caractérisation magnétique fournit des informations précieuses sur la réduction du catalyseur, la taille des nanoparticules ferromagnétiques, la chimisorption, ainsi que sur les réactions topochimiques qui se produisent avec les catalyseurs au cours de la genèse de la phase active et dans des conditions réactionnelles. Les possibilités et les limites de la méthode magnétique sont examinées. Abstract -Magnetic Characterization of Fischer-Tropsch Catalysts -This paper reviews recent developments in the application of magnetic methods for investigation of Fischer

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Synchrotron Radiation and Oil Industry Research

Cited by 4 publications

References 58 publications

X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

X-ray Absorption Investigation of the Formation of Cobalt Ferrite Nanoparticles in an Aerogel Silica Matrix

Advances in the Development of Novel Cobalt Fischer−Tropsch Catalysts for Synthesis of Long-Chain Hydrocarbons and Clean Fuels

F ischer‐ T ropsch Process

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