The role of surface structure and dispersion in CO hydrogenation on cobalt

Johnson, B. G.

doi:10.1016/0021-9517(91)90080-n

Cited by 157 publications

(36 citation statements)

References 38 publications

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“…Iglesia et al established that neither the nature of the support nor the dispersion of Co particles influenced turnover frequency (TOF) of these catalysts, but it was proportional to the concentration of active sites on the surface [4][5][6]. Johnson et al [7] agree with the fact that TOF was not affected by dispersion, although CO conversion seemed to be strongly dependent on Co reducibility. However, Reuel and Bartholomew [8] or Bessell [9] exposed that both low metal-support interactions and high dispersion are required parameters to obtain a really active cobalt based catalyst.…”

Section: Introductionsupporting

confidence: 64%

Influence of Cobalt Precursor on Efficient Production of Commercial Fuels over FTS Co/SiC Catalyst

et al. 2016

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β-SiC-supported cobalt catalysts have been prepared from nitrate, acetate, chloride and citrate salts to study the dependence of Fischer-Tropsch synthesis (FTS) on the type of precursor. Com/SiC catalysts were synthetized by vacuum-assisted impregnation while N 2 adsorption/desorption, XRD, TEM, TPR, O 2 pulses and acid/base titrations were used as characterization techniques. FTS catalytic performance was carried out at 220˝C and 250˝C while keeping constant the pressure (20 bar), space velocity (6000 Ncm 3 /g¨h) and syngas composition (H 2 /CO:2). The nature of cobalt precursor was found to influence basic behavior, extent of reduction and metallic particle size. For β-SiC-supported catalysts, the use of cobalt nitrate resulted in big Co crystallites, an enhanced degree of reduction and higher basicity compared to acetate, chloride and citrate-based catalysts. Consequently, cobalt nitrate provided a better activity and selectivity to C 5 + (less than 10% methane was formed), which was centered in kerosene-diesel fraction (α = 0.90).On the contrary, catalyst from cobalt citrate, characterized by the highest viscosity and acidity values, presented a highly dispersed distribution of Co nanoparticles leading to a lower reducibility. Therefore, a lower FTS activity was obtained and chain growth probability was shortened as observed from methane and gasoline-kerosene (α = 0.76) production when using cobalt citrate.

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Section: Introductionsupporting

confidence: 64%

Influence of Cobalt Precursor on Efficient Production of Commercial Fuels over FTS Co/SiC Catalyst

et al. 2016

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“…Indeed, the results reported by den Breejen et al [67] are issued from cobalt nanoparticles deposited on carbon nanofibers with peculiar prismatic planes, and thus, some specific interaction could also influence the FTS performance compared to the results reported on cobalt supported on other supports such as silica, alumina, or titania. Johnson et al [68] have reported that FTS can be structure-insensitive under certain reaction conditions and the FTS activity and selectivity were function of the chemical nature of the support instead of the cobalt dispersion and size. Similar results have also been reported by Borg et al [69] who observed no direct relationship between the FTS activity and the cobalt particle size.…”

Section: Discussionmentioning

confidence: 99%

Efficient hierarchically structured composites containing cobalt catalyst for clean synthetic fuel production from Fischer–Tropsch synthesis

Liu

Luo

Gîrleanu

et al. 2014

Journal of Catalysis

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Co zero field NMR a b s t r a c tWe report a straightforward preparation method to synthesize hierarchical composite consisting of TiO 2coated multi-walled carbon nanotubes (CNTs) decorating a macroscopic host structure of a-Al 2 O 3 . The obtained composite possesses moderate specific surface area and very open porous structure, as well as moderate interaction with active sites, which significantly improve the cobalt nanoparticles dispersion and the mass diffusion during the reaction. The Co/TiO 2 /CNT-a-Al 2 O 3 (CoTiCNTA) catalyst is then used in the Fischer-Tropsch synthesis (FTS) process. This hierarchical catalyst achieves a FTS rate to C 5+ of 0.80 g C5+ g cat À1 h À1 along with a long-chain hydrocarbons (C 5+ ) selectivity of 85%, which can be pointed out as the most outstanding noble promoter-free catalyst for the FTS process. The as-synthesized catalyst also exhibits an extremely high stability as a function of time on stream which is also one of the prerequisites for the development of future FTS catalysts, especially for the Biomass-to-Liquids process where trace amount of impurities and/or moisture could have an impact on the catalyst stability. The present work also introduces a new investigation methodology based on the use of zero field 59 Co NMR, which allows one to map in a precise manner the cobalt active phase distribution and to correlate it with the FTS performance. It is expected that such technique would be extremely helpful for the understanding of the catalyst structure-performance relationship and for future optimization in the FTS process as well as in other fields of investigation where cobalt particles are involved.

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“…[10] The results diverge over smaller Co particles, and some research groupsh ave reported ad ecreaseo ft he TOF with decreasing particle size, [6,7,9,14] whereas others do not observe this effect. [3,4,12,13] The cause for this discrepancy has been attributed to al arge range of phenomena such as ap referential oxidation or carbidization of small Co particles, difference in reducibility,f ormation of Co-support mixed compounds, or to an inappropriatem easurement of the surfaceC oa toms. For the latter issue, Yang et al have compared H 2 and CO chemisorption methods to determine the Co particles ize.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous studies have been devoted to gain an understanding of the effect of the support and Co structure on the catalytic performance. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] The precise influence of the catalyst variables remains unclear.T he effect of the Co particles ize on the activity and selectivity is still under debate.…”

Section: Introductionmentioning

confidence: 99%

Measurement of the Influence of the Microstructure of Alumina‐Supported Cobalt Catalysts on their Activity and Selectivity in Fischer–Tropsch Synthesis by using Steady‐State and Transient Kinetics

et al. 2017

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Five alumina‐supported Co catalysts with different particle sizes and structures were synthesized. The catalysts showed different activities during long‐term Fischer–Tropsch experiments. Steady‐state isotopic transient kinetic analysis (SSITKA) 12CO/H2→13CO/H2 experiments were performed during these long‐term runs. The number of active sites for CO adsorption and activation was estimated through the summation of all surface intermediates derived from the SSITKA results. Rather than comparing turnover frequencies, a kinetic analysis was performed. A simple kinetic rate equation based on the in situ number of active sites described the steady‐state CO conversion over the five catalysts adequately. Thus the difference in the catalytic performance could not be attributed to a difference in particle size, phase orientation (face‐centered cubic or hexagonal close packed), or Pt‐promotion effect but instead was only because of the number of reduced Co atoms exposed during the reaction. Similarly, the selectivity depended on the CO conversion level and temperature and not on the catalyst structure.

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The role of surface structure and dispersion in CO hydrogenation on cobalt

Cited by 157 publications

References 38 publications

Influence of Cobalt Precursor on Efficient Production of Commercial Fuels over FTS Co/SiC Catalyst

Influence of Cobalt Precursor on Efficient Production of Commercial Fuels over FTS Co/SiC Catalyst

Efficient hierarchically structured composites containing cobalt catalyst for clean synthetic fuel production from Fischer–Tropsch synthesis

Measurement of the Influence of the Microstructure of Alumina‐Supported Cobalt Catalysts on their Activity and Selectivity in Fischer–Tropsch Synthesis by using Steady‐State and Transient Kinetics

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