Catalyst Particle Size of Cobalt/Rhenium on Porous Alumina and the Effect on Fischer−Tropsch Catalytic Performance

Rytter, Erling; Eri, Sigrid; Skagseth, Torild Hulsund; Schanke, Dag; Bergene, Edvard; Myrstad, Rune; Lindvåg, Asbjørn

doi:10.1021/ie071136+

Cited by 54 publications

(43 citation statements)

References 16 publications

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“…The activity of the catalyst in FTS largely depends on the degree of reduction of the metal precursor. The shape and size of the metal particles, which control the number of active sites is also important [12]. A considerable amount of discussion has gone into establishing the existence of structure sensitivity or not in supported Co catalysts during the FTS.…”

Section: Resultsmentioning

confidence: 99%

Controlled Nanocrystal Deposition for Higher Degree of Reduction in Co/Al2O3 Catalyst

et al. 2009

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Alumina supported 5% Co catalyst was prepared, by the controlled nanocrystal deposition method using oleic acid as a capping agent, and tested for its activity and selectivity in Fischer-Tropsch synthesis. The catalyst exhibited facile reducibility of the cobalt species. The CO conversion and C 5? selectivity obtained on this size-controlled catalyst were higher than those observed on the catalysts prepared by impregnation and precipitation techniques. Decrease in the mobility of the nanoparticle towards the tetrahedral sites of alumina could be the reason for high reducibility, as the formation of cobalt aluminate was found to be considerably reduced during temperature programmed reduction.

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Section: Resultsmentioning

confidence: 99%

Controlled Nanocrystal Deposition for Higher Degree of Reduction in Co/Al2O3 Catalyst

et al. 2009

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“…The Barrett-Joyner-Halenda model assumes presence of only cylindrical pores and absence of pore networks. In reality, no simple pore geometry exists as demonstrated by Rytter et al [22]. Transmission electron microscopy images of the Co/c-Al 2 O 3 interphase showed that the alumina crystallites were entangled into each other in what appeared to be a chaotic fashion.…”

Section: X-ray Diffractionmentioning

confidence: 96%

Electron Microscopy Study of γ-Al2O3 Supported Cobalt Fischer–Tropsch Synthesis Catalysts

et al. 2008

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Three supported catalysts containing 20 wt% cobalt and 0.5 wt% rhenium were subjected to electron microscopy studies in their calcined state. The catalysts were prepared by incipient wetness impregnation of c-Al 2 O 3 supports of different pore characteristics with aqueous solutions of cobalt nitrate hexahydrate and perrhenic acid. The influence of the support on the Co 3 O 4 crystallite size and distribution was studied by X-ray diffraction and electron microscopy. There was a positive correlation between the pore diameter of the support and the post calcination Co 3 O 4 crystallite size. On all three c-Al 2 O 3 supports, Co 3 O 4 was present as aggregates of many crystallites (20-270 nm in size). Cobalt oxide did not crystallise as independent crystallites, but as an interconnected network, with a roughly common crystallographic orientation, within the matrix pore structure. The internal variations in crystallite size between the catalysts were maintained after reduction. Fischer-Tropsch synthesis was carried out in a fixed-bed reactor at industrial conditions (T = 483 K, P = 20 bar, H 2 /CO = 2.1). Although the cobalt-time yields varied significantly (4.6-6.7 9 10 -3 mol CO/mol Co s), the site-time yields were constant (63-68 9 10 -3 s -1 ) for the three samples. The C 5? selectivity could not be correlated to the cobalt oxide aggregate size and is more likely related to the cobalt particle size and chemical properties of the c-Al 2 O 3 support.

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“…Olefins can also be hydrogenated in a secondary reaction. There is evidence from experiments at low conversion and small catalyst particle size that the primary product is dominated by olefins, but for practical purposes the olefin to paraffin ratio is well above two for C3 and then diminishes rapidly with chain length [12].…”

Section: Catalyst Activitymentioning

confidence: 99%

“…It has been shown that above ca. 200 µm particle size the higher effective H2/CO ratio in the inner part of the pellets significantly reduces C5+ yield [12]. Therefore, an egg-shell catalyst design is preferred where only the outer parts are impregnated with active metal.…”

Section: Fischer-tropsch Reactorsmentioning

confidence: 99%

“…Great care must be taken to obtain a homogeneous catalyst material, but the targeted distribution of cobalt on the support depends on the actual process. For slurry catalysts with diameters typically in the range 40-120 µm pore diffusion resistance of the syngas is negligible ensuring full utilization of the available surface area [12]. For micro-channel reactors the catalyst either will resemble a slurry catalyst or be impregnated onto special trays that are inserted into the channels.…”

Section: Commercial Catalyst Formulationsmentioning

confidence: 99%

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Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts—A Mini-Review

2015

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Deactivation of commercially relevant cobalt catalysts for Low Temperature Fischer-Tropsch (LTFT) synthesis is discussed with a focus on the two main long-term deactivation mechanisms proposed: Carbon deposits covering the catalytic surface and re-oxidation of the cobalt metal. There is a great variety in commercial, demonstration or pilot LTFT operations in terms of reactor systems employed, catalyst formulations and process conditions. Lack of sufficient data makes it difficult to correlate the deactivation mechanism with the actual process and catalyst design. It is well known that long term catalyst deactivation is sensitive to the conditions the actual catalyst experiences in the reactor. Therefore, great care should be taken during start-up, shutdown and upsets to monitor and control process variables such as reactant concentrations, pressure and temperature which greatly affect deactivation mechanism and rate. Nevertheless, evidence so far shows that carbon deposition is the main long-term deactivation mechanism for most LTFT operations. It is intriguing that some reports indicate a low deactivation rate for multi-channel micro-reactors. In situ rejuvenation and regeneration of Co catalysts are economically necessary for extending their life to several years. The review covers information from open sources, but with a particular focus on patent literature.

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Catalyst Particle Size of Cobalt/Rhenium on Porous Alumina and the Effect on Fischer−Tropsch Catalytic Performance

Cited by 54 publications

References 16 publications

Controlled Nanocrystal Deposition for Higher Degree of Reduction in Co/Al2O3 Catalyst

Controlled Nanocrystal Deposition for Higher Degree of Reduction in Co/Al2O3 Catalyst

Electron Microscopy Study of γ-Al2O3 Supported Cobalt Fischer–Tropsch Synthesis Catalysts

Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts—A Mini-Review

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