Addition of Acetylene to the Fischer−Tropsch Reaction

Hou, Li; Tierney, and John W.; Wender, I.

doi:10.1021/ef060497j

Cited by 9 publications

(4 citation statements)

References 43 publications

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“…46,47 Under FT synthesis conditions, acetylenelike intermediates are effectively incorporated in FT products, acting mainly as chain initiators. 48 Thus, catalyst deactivation by the described mechanism is expected to be a minor side reaction, making carbon build-up on the Co catalyst a slow process.…”

Section: ■ Discussionmentioning

confidence: 96%

“…Thus, during FT synthesis, step edges and other types of defects on the cobalt surface are expected to play a crucial role as nucleation sites for graphene, while growth primarily proceeds via insertion of C 2 H x intermediates. Graphene formation at step edges is seen as a particularly unwanted reaction, as these sites are crucial for activation of the CO molecule. , Under FT synthesis conditions, acetylene-like intermediates are effectively incorporated in FT products, acting mainly as chain initiators . Thus, catalyst deactivation by the described mechanism is expected to be a minor side reaction, making carbon build-up on the Co catalyst a slow process.…”

Section: Discussionmentioning

confidence: 99%

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Atomic and Polymeric Carbon on Co(0001): Surface Reconstruction, Graphene Formation, and Catalyst Poisoning

et al. 2012

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Atomic carbon on Co(0001), deposited by ethylene decomposition, forms islands with a (√3 × √3)R30°structure at low C coverage (∼0.2 ML), whereas a high C coverage (0.5 ML, saturation) induces a reconstruction of the cobalt surface. Atomic carbon weakens the adsorption of CO and H 2 , but even a saturated atomic carbon layer does not block the surface for adsorption. Carbon−carbon coupling, i.e., polymeric carbon formation, was not observed for temperatures ≤630 K on the close-packed cobalt surface. Polymeric carbon, in the form of small graphene islands, forms on the close-packed terraces after heating of an acetylene-saturated surface. Graphene also forms upon heating of an atomic carbon covered surface on which ethylene was dosed at low temperature. In this case, step edges act as a nucleation point of the graphene islands, while their growth proceeds via the addition of C 2 H x species. In both cases, hydrogenated forms of carbon rather than atomic carbon are key precursors for graphene growth. Graphene covers the cobalt surface, thereby inhibiting adsorption of CO and hydrogen completely. The described graphene formation mechanism is seen as a relevant, low temperature route to detrimental carbon that would deactivate a cobalt FT catalyst. Atomic carbon is more reactive than graphene, as it is oxidized at lower temperatures than graphene. The graphene islands formed at relatively low temperatures are of poor structural quality and contain (islands of) encapsulated cobalt atoms.

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Section: ■ Discussionmentioning

confidence: 96%

Section: Discussionmentioning

confidence: 99%

Atomic and Polymeric Carbon on Co(0001): Surface Reconstruction, Graphene Formation, and Catalyst Poisoning

et al. 2012

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“…Starting from CH 3 CH, the formation of CH 2 CH is most favored kinetically. In addition, CH 2 CH 2 or HCCH, participating in the chain growth process, 61,64–66 only can be formed from the dehydrogenation of CH 3 CH 2 or CH 2 CH, and the hydrogenation of CH 2 CH or HCC based on the above discussion. However, the formation of CH 3 CH 2 or HCC is kinetically not favored, compared with the formation of CH 2 CH (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…On cobalt catalysts, the addition of labeled 14 C–HCCH into synthesis gas (453 K, 2.07 atm, p CO / p H 2 / p Ar / p HCCH = 44/45/10/1) resulted in a significant increase in C2–C11 product yield, demonstrating its promotion effect. Even when the temperature drops to 393 K, at which the cobalt catalysts are inactive, 65,66 HCCH can promote carbon chain growth. Upon the conversion of HCCH to CH 3 C on metal surfaces, 69 they claimed such conversion over a cobalt catalyst.…”

Section: Resultsmentioning

confidence: 99%