On the selectivity of cobalt-based Fischer–Tropsch catalysts: Evidence for a common precursor for methane and long-chain hydrocarbons

Lögdberg, Sara; Lualdi, Matteo; Järås, Sven; Walmsley, John C.; Blekkan, Edd A.; Rytter, Erling; Holmén, Anders

doi:10.1016/j.jcat.2010.06.007

Cited by 92 publications

(73 citation statements)

References 59 publications

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“…In a recent study [1], we found a specific interdependence between hydrocarbon selectivities to C 1 , C 2 , C 3 , C 4 and C 5? irrespective of the physicochemical properties of Co-based catalysts supported on c-Al 2 O 3 , a-Al 2 O 3 and TiO 2 . Moreover, chain-growth probabilities for C Ã n surface intermediates, aC n values, were calculated for n = 1-4 showing linear correlations with S C 5þ .…”

Section: Introductionmentioning

confidence: 68%

Evidence for Diffusion-Controlled Hydrocarbon Selectivities in the Fischer–Tropsch Synthesis Over Cobalt Supported on Ordered Mesoporous Silica

et al. 2011

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A series of four cobalt-based catalysts (two of which promoted with ruthenium) supported on SiO 2 or SBA-15 were prepared and tested in the Fischer-Tropsch synthesis at industrially relevant process conditions (483 K, 20 bar, H 2 /CO ratio = 2.1, pellet size: 53-90 lm). The catalysts were characterized by N 2 -adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), H 2 -chemisorption and transmission electron microscopy (TEM). Ru as promoter enhanced the activity but not the selectivity to long-chain hydrocarbons (S C 5þ ). The S C 5þ values of the SBA-supported catalysts were very low, especially at low conversion levels (i.e. low water partial pressure), suggesting that CO diffusion limitation increased the H 2 /CO ratio inside the 1-dimensional (1-D) porous network. A superimposition of the selectivity results on the correlations found in our recent study, derived for Co-based catalysts supported on c-Al 2 O 3 , a-Al 2 O 3 and TiO 2 free from diffusion limitations, was made. While the SiO 2 -supported catalysts with a 3-D porous structure followed the correlations, the SBA-catalysts deviated significantly at low conversions, giving a further indication that the selectivity results of these catalysts were affected by CO diffusion limitations. Hence, it may be concluded that the kinetically significant diffusion distances (i.e. those long enough to cause an intrapore H 2 / CO ratio higher than that of the bulk gas phase) are probably much shorter for 1-D porous networks than for conventional 3-D supports. This is explained by a significantly lower effective diffusivity in 1-D porous networks. The potential of using the correlations between non-ASF distributed hydrocarbons and C 5? , to give insight on the occurrence of diffusion limitations, was confirmed by superimposing data from the literature that were anticipated to be influenced by CO diffusion limitations.

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Section: Introductionmentioning

confidence: 68%

Evidence for Diffusion-Controlled Hydrocarbon Selectivities in the Fischer–Tropsch Synthesis Over Cobalt Supported on Ordered Mesoporous Silica

et al. 2011

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“…The chemisorption measurement was conducted on a Micromeritics ASAP 2020C unit at 308 K, after reducing about 0.15 g of the calcined catalyst in flowing hydrogen at 623 K (heating rate: 1 K/min) for 16 h according to the procedure described in refs. [20,25]. The average particle size of Co 0 , assuming spherical shape, was estimated according to [26][27][28]:…”

Section: Catalyst Characterization Methodsmentioning

confidence: 99%

Investigation of Mixtures of a Co-Based Catalyst and a Cu-Based Catalyst for the Fischer–Tropsch Synthesis with Bio-Syngas: The Importance of Indigenous Water

et al. 2011

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A series of different mechanical mixtures of a narrow-pore Co/c-Al 2 O 3 catalyst and a Cu-based WGScatalyst has been investigated in the low-temperature Fischer-Tropsch synthesis (483 K, 20 bar) with a model bio-syngas (H 2 /CO = 1.0) in a fixed-bed reactor. The higher the fraction of WGS-catalyst in the mixture, the lower is the Co-catalyst-time yield to hydrocarbons. This is ascribed to a strong positive kinetic effect of water on the Fischer-Tropsch rate of the Co-catalyst, showing the importance of the indigenously produced water, especially in fixed-bed reactors where the partial pressure of water is zero at the reactor inlet. A preliminary kinetic modeling suggests that the reaction order in P H 2 O is 0.3 for the Co/ c-Al 2 O 3 catalyst in the range of the studied reactor-average partial pressures of water (i.e., 0.04-1.2 bar).

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“…The Co 3 O 4 crystallite diameter [d(Co 3 O 4 ) XRD , nm] was estimated by using the Scherrer equation and assuming spherical crystallites and applying a correction factor of 4/3 [37,38]. The cobalt crystallite size [(dCo 0 ) XRD , nm] was estimated from that of Co 3 O 4 according to the relative molar volumes of Co 0 and Co 3 O 4 using the following formula [7]:…”

Section: X-ray Diffractionmentioning

confidence: 99%

Fischer–Tropsch Synthesis Over Zr-Promoted Co/γ-Al2O3 Catalysts

Barrientos

Garcilaso²,

Venezia

et al. 2017

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On the selectivity of cobalt-based Fischer–Tropsch catalysts: Evidence for a common precursor for methane and long-chain hydrocarbons

Cited by 92 publications

References 59 publications

Evidence for Diffusion-Controlled Hydrocarbon Selectivities in the Fischer–Tropsch Synthesis Over Cobalt Supported on Ordered Mesoporous Silica

Evidence for Diffusion-Controlled Hydrocarbon Selectivities in the Fischer–Tropsch Synthesis Over Cobalt Supported on Ordered Mesoporous Silica

Investigation of Mixtures of a Co-Based Catalyst and a Cu-Based Catalyst for the Fischer–Tropsch Synthesis with Bio-Syngas: The Importance of Indigenous Water

Fischer–Tropsch Synthesis Over Zr-Promoted Co/γ-Al2O3 Catalysts

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