The State of Nickel as Promotor in Cobalt Fischer–Tropsch Synthesis Catalysts

Voss, Georg; Fløystad, Jostein Bø; Voronov, Alexey; Rønning, Magnus

doi:10.1007/s11244-015-0456-z

Cited by 17 publications

(10 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…These results suggest that approximately 50 % of the Ni 2+ present in the support was reduced along with Co, with a moderate impact on the activity and selectivity toward lighter hydrocarbons. Ni has been reported to be a reduction and catalytic promoter of Co on FT catalysts . Ni‐Co phases provide a higher activity than the Co/γ‐Al 2 O 3 homologue, however, in some occurrences, at the cost of a lower selectivity in heavier hydrocarbons .…”

Section: Resultsmentioning

confidence: 99%

Inhibition by Inorganic Dopants of γ‐Alumina Chemical Weathering under Hydrothermal Conditions: Identification of Reactive Sites and their Influence in Fischer–Tropsch Synthesis

et al. 2017

View full text Add to dashboard Cite

Understanding how alumina degradation to boehmite AlOOH can be prevented under hydrothermal conditions is key to design more stable catalysts supported on alumina for Fischer–Tropsch synthesis. We compare the effect of four inorganic dopants to inhibit γ‐alumina chemical weathering under hydrothermal conditions: three metal ions: Mg2+, Zr4+, Ni2+, introduced by impregnation, and nonmetal Si, introduced by the grafting of tetraethyl orthosilicate. Boehmite is formed by a mechanism of dissolution–precipitation. A significant decrease of alumina weathering to boehmite is evidenced for all dopants. For metal ions, the thermal conversion of doped γ‐Al2O3 into an alumina‐rich mixed oxide or the coverage of the alumina surface by particles of a poorly soluble oxide such as NiO contribute to the stabilization of the solid. Alumina dissolution and degradation are only inhibited fully through Si grafting. IR spectra in the OH stretching region suggest that the most reactive alumina sites toward dissolution are basic Al−OH sites located on lateral facets that are blocked upon Si introduction. Fischer–Tropsch reactivity shows that Co catalysts prepared on Mg2+‐ and Si‐doped supports are less active or, at best, as active as a reference Co/γ‐Al2O3 catalyst, which is explained by a lower reducibility of CoO on doped supports. The Co catalyst prepared on Mg2+‐doped γ‐Al2O3 calcined at 900 °C exhibits the best combination of catalytic activity, ease of preparation, and hydrothermal stability.

show abstract

Section: Resultsmentioning

confidence: 99%

Inhibition by Inorganic Dopants of γ‐Alumina Chemical Weathering under Hydrothermal Conditions: Identification of Reactive Sites and their Influence in Fischer–Tropsch Synthesis

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The reduction of cobalt oxide is shifted to a lower temperature with increasing Ni/Co ratio, and the percentage of metal reduction is increased. Voss et al [19] observed an improvement in the reducibility when nickel was added, as the first reduction step shifted to a significantly lower temperature with increasing the nickel loading. The authors proposed a hydrogen spillover effect from the nickel sites to cobalt oxide sites.…”

Section: Discussionmentioning

confidence: 99%

Substitution of Co with Ni in Co/Al2O3 Catalysts for Fischer–Tropsch Synthesis

et al. 2020

View full text Add to dashboard Cite

The effect of cobalt substitution with nickel was investigated for the Fischer–Tropsch synthesis reaction. Catalysts having different Ni/Co ratios were prepared by aqueous incipient wetness co-impregnation, characterized, and tested using a continuously stirred tank reactor (CSTR) for more than 200 h. The addition of nickel did not significantly modify the morphological properties measured. XRD, STEM, and TPR-XANES results showed intimate contact between nickel and cobalt, strongly suggesting the formation of a Co-Ni solid oxide solution in each case. Moreover, TPR-XANES indicated that nickel addition improves the cobalt reducibility. This may be due to H2 dissociation and spillover, but is more likely the results of a chemical effect of intimate contact between Co and Ni resulting in Co-Ni alloying after activation. FTS testing revealed a lower initial activity when nickel was added. However, CO conversion continuously increased with time on-stream until a steady-state value (34%–37% depending on Ni/Co ratio) was achieved, which was very close to the value observed for undoped Co/Al2O3. This trend suggests nickel can stabilize cobalt nanoparticles even at a lower weight percentage of Co. Currently, the cobalt price is 2.13 times the price of nickel. Thus, comparing the activity/price, the catalyst with a Ni/Co ratio of 25/75 has better performance than the unpromoted catalyst. Finally, nickel-promoted catalysts exhibited slightly higher initial selectivity for light hydrocarbons, but this difference typically diminished with time on-stream; once leveling off in conversion was achieved, the C5+ selectivities were similar (≈ 80%) for Ni/Co ratios up to 10/90, and only slightly lower (≈ 77%) at Ni/Co of 25/75.

show abstract

“…The smallest particles were obtained at intermediate Co–Ni compositions, that is, at Ni/(Ni + Co) of 0.5 atom/atom for TiO 2 and 0.75 atom/atom for Nb 2 O 5 and α-Al 2 O 3 . Thus, metal nanoparticle dispersion on the oxidic supports was enhanced by addition of nickel, as suggested by the H 2 chemisorption measurements and in accordance with previous reports. , …”

Section: Resultsmentioning

confidence: 99%

Cobalt–Nickel Nanoparticles Supported on Reducible Oxides as Fischer–Tropsch Catalysts

et al. 2020

View full text Add to dashboard Cite

Efficient and more sustainable production of transportation fuels is key to fulfill the ever-increasing global demand. In order to achieve this, progress in the development of highly active and selective catalysts is fundamental. The combination of bimetallic nanoparticles and reactive support materials offers unique and complex interactions that can be exploited for improved catalyst performance. Here, we report on cobalt−nickel nanoparticles on reducible metal oxides as support material for enhanced performance in the Fischer−Tropsch synthesis. For this, different cobalt to nickel ratios (Ni/(Ni + Co): 0.0, 0.25, 0.50, 0.75, or 1.0 atom/atom) supported on reducible (TiO 2 and Nb 2 O 5 ) or nonreducible (α-Al 2 O 3 ) oxides were studied. At 1 bar, Co−Ni nanoparticles supported on TiO 2 and Nb 2 O 5 showed stable catalytic performance, high activities and remarkably high selectivities for long-chain hydrocarbons (C 5+ , ∼80 wt %). In contrast, catalysts supported on α-Al 2 O 3 independently of the metal composition showed lower activities, high methane production, and considerable deactivation throughout the experiment. At 20 bar, the combination of cobalt and nickel supported on reducible oxides allowed for 25−50% cobalt substitution by nickel with increased Fischer−Tropsch activity and without sacrificing much C 5+ selectivity. STEM-EDX and IR of adsorbed CO pointed to a cobalt enrichment of the nanoparticle's surface and a weaker adsorption of CO in Co−Ni supported on TiO 2 and Nb 2 O 5 and not on α-Al 2 O 3 , modifying the rate-determining step and the catalytic performance. Overall, we show the strong effect and potential of reducible metal oxides as support materials for bimetallic nanoparticles for enhanced catalytic performance.

show abstract

The State of Nickel as Promotor in Cobalt Fischer–Tropsch Synthesis Catalysts

Cited by 17 publications

References 20 publications

Inhibition by Inorganic Dopants of γ‐Alumina Chemical Weathering under Hydrothermal Conditions: Identification of Reactive Sites and their Influence in Fischer–Tropsch Synthesis

Inhibition by Inorganic Dopants of γ‐Alumina Chemical Weathering under Hydrothermal Conditions: Identification of Reactive Sites and their Influence in Fischer–Tropsch Synthesis

Substitution of Co with Ni in Co/Al2O3 Catalysts for Fischer–Tropsch Synthesis

Cobalt–Nickel Nanoparticles Supported on Reducible Oxides as Fischer–Tropsch Catalysts

Contact Info

Product

Resources

About