Further insights into methane and higher hydrocarbons formation over cobalt-based catalysts with γ-Al2O3, α-Al2O3 and TiO2 as support materials

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

doi:10.1016/j.jcat.2017.06.003

Cited by 30 publications

(26 citation statements)

References 83 publications

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“…As the catalyst activity increases, more monomers are formed giving higher concentration of the CHx pool. [47] These monomers are then more easily incorporated into the growing chain. [48,49] In both the previous work of Lögdberg et al, [45] and in the present work there is a slight increase in α1 with higher C5+.…”

Section: Chain Propagation Probabilitiesmentioning

confidence: 99%

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Water as key to activity and selectivity in Co Fischer-Tropsch synthesis: γ-alumina based structure-performance relationships

Rytter

Borg

Tsakoumis

et al. 2018

Journal of Catalysis

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Thirteen γ-alumina supports with different pore sizes and pore size distributions have been impregnated with cobalt and rhenium. The catalysts were tested for Fischer-Tropsch synthesis (FTS) under dry and enhanced water vapor pressure conditions. It is shown that there is a positive correlation between pore size and cobalt crystallite size of the reduced catalyst after incipient wetness impregnation as long as the pore size distribution is sufficiently narrow. There is a concurrent increase in C5+ with pore diameter due to higher chain propagation probabilities α3+. Higher α values are ascribed to larger cobalt crystallites that promote CO activation resulting in higher surface coverage of CHx monomers. Adding water vapor to the syngas feed has a strong positive effect on selectivity to higher hydrocarbons and activity. Water imposes a significant enhancement of α1 that is attributed to higher relative cobalt surface coverage of H2O(OH-) and CHx relative to hydrogen. Small pores are susceptible to condensation of water during FTS.

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Section: Chain Propagation Probabilitiesmentioning

confidence: 99%

“…A well-defined linear correlation was previously found between the C5+ selectivity and α4. [45,47] Figure 15c indicates that this statement should be modified. Four distinct trendlines are found to describe the data.…”

Section: Chain Propagation Probabilitiesmentioning

confidence: 99%

Water as key to activity and selectivity in Co Fischer-Tropsch synthesis: γ-alumina based structure-performance relationships

Rytter

Borg

Tsakoumis

et al. 2018

Journal of Catalysis

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“…We propose that the existence of strong primary hydrogenation function is rather localized (few sites producing methane at high rates) since these catalysts retain high o/p ratios. The B category catalysts outperform the other tested materials in all performance indicators (Table 1) and can be compared with the superior performance of α-Al 2 O 3 and TiO 2 supported Co NPs 44 . Following this pretreatment, the Co crystallites are rich in hcp-Co, with indications of stacking disorder and small contributions from fcc-Co ( Figure S2).…”

Section: Figure 2 Structural Evolution Obtained From Refinement Of Imentioning

confidence: 93%

“…Exceptions from the observed improved performance of the hcp-Co NPs are found for the αC 1 values, which appear invariant. On a big sample of selectivity data from conventional Co-based FT catalysts that share support and have been measured at identical process conditions, an inverse relationship between higher αC n values (n > 1) and αC 1 has been found 44 . Here, comparing with the FT results of the REF catalyst it is apparent that the change from fcc rich hybrid fcc/hcp-Co to hcp-Co NPs increases most performance indicators (i.e.…”

Section: Figure 2 Structural Evolution Obtained From Refinement Of Imentioning

confidence: 95%

“…Figure 3a compares the SC 5+ vs. SC 1 values for the RCR catalysts with literature data for conventional catalysts with Co NPs > 6 nm at the same experimental conditions and conversion level. The scattering in the literature data is due to both experimental error (2, see supporting information) and actual differences in αC 1 ranging from 0.52 to 0.57 44 . Here, values from B and C category catalysts with the αC 1 values in the range (0.53 to 0.54) are following the trendline of the literature data, suggesting that the surface-crowding mechanism is valid.…”

Section: Figure 2 Structural Evolution Obtained From Refinement Of Imentioning

confidence: 99%

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Structure–Performance Relationships on Co-Based Fischer–Tropsch Synthesis Catalysts: The More Defect-Free, the Better

et al. 2018

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Understanding and utilizing structureperformance relationships in catalytic nanomaterials is the epitome of catalysis science. Knowledge at the atomic level can potentially allow rational design of more selective and energy efficient catalytic materials. Fischer-Tropsch synthesis on cobalt is an example of a complicated system that operates in a narrow process regime, and the nature of the reaction product is governed by numerous parameters. On an industrial model catalyst, we have simplified the structure of the active, metallic nanoparticles into predominantly hexagonal close packed structure via the use of a Co 2 C precursor. By varying the final reduction temperature, we could mildly modify catalyst microstructural properties at the nanoparticle (NP) level. Catalytic materials, although with minimal structural differences, showed significantly different performance. Evidently there is a narrow window for complete utilization of the hexagonal close packed Co crystallites that lays between removal of lattice carbon, that remains from the Co 2 C precursor, and the initiation of stacking disorder, due to transition to the face centered cubic Co structure. Fischer-Tropsch synthesis performance indicators show that Co NPs with minimum number of crystal defects outperform catalysts with lattice defects, either due to the existence of lattice carbon or stacking faults. Therefore, catalyst preparation and activation procedures probably should be designed targeting defect free Co crystallites.

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Characteristics of integral plasma-fluidized bed and preparation of Mo-based catalysts for sulfur-resistant methanation

Wang,

Kong,

2024

Reac Kinet Mech Cat

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Further insights into methane and higher hydrocarbons formation over cobalt-based catalysts with γ-Al2O3, α-Al2O3 and TiO2 as support materials

Cited by 30 publications

References 83 publications

Water as key to activity and selectivity in Co Fischer-Tropsch synthesis: γ-alumina based structure-performance relationships

Water as key to activity and selectivity in Co Fischer-Tropsch synthesis: γ-alumina based structure-performance relationships

Structure–Performance Relationships on Co-Based Fischer–Tropsch Synthesis Catalysts: The More Defect-Free, the Better

Characteristics of integral plasma-fluidized bed and preparation of Mo-based catalysts for sulfur-resistant methanation

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