Group 11 (Cu, Ag, Au) promotion of 15%Co/Al2O3 Fischer–Tropsch synthesis catalysts

Jacobs, Gary; Ribeiro, Mauro C.; Ma, Wanhong; Ji, Yaying; Khalid, Syed; Sumodjo, Paulo Teng An; Davis, Burtron H.

doi:10.1016/j.apcata.2009.04.007

Cited by 95 publications

(56 citation statements)

References 38 publications

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“…Cu, Ag, and Au (Group IB) promoters are also effective at promoting the reduction of cobalt oxides, as described in Figure 1 (top) [10]. However, note that the loadings indicated by the solid lines are approximately three times higher on an atomic basis than those of the commonly used promoters (Pt, Re, Ru) shown in the lower part of the figure.…”

Section: Resultsmentioning

confidence: 72%

“…Table 1 shows a comparison of X CO at the same weight hourly space velocity of two Cu-promoted 15%Co/Al 2 O 3 catalysts relative to the unpromoted 15%Co/Al 2 O 3 catalyst. Despite increases in metal site densities as measured by hydrogen TPD, a decrease in X CO is observed, which is exacerbated at higher Cu loading [10]. These results suggest a poisoning of surface Co sites, likely due to enrichment of Cu at the surface.…”

Section: Example #1-coppermentioning

confidence: 64%

“…With increases in extent of reduction of cobalt (from 49.8% for 15%Co/Al 2 O 3 to 53.2, 69.4, and 93.3% for 0.033%, 0.49%, and 1.63% Cu-promoted 15%Co/Al 2 O 3 catalysts, respectively) the active metal site densities with Cu addition increased also, and hydrogen chemisorption uptakes measured by TPD increased from 72 μmol H 2 /g cat for the unpromoted 15%Co/Al 2 O 3 catalyst to 82, 140, and 172 μm H 2 /g cat for the 0.033%, 0.49%, and 1.63% Cu-promoted 15%Co/Al 2 O 3 catalysts [10]. However, the metal dispersions do not account for the partitioning of metal type on the surface of Co particles, or the influence of the presence of Cu on the ensembles of Co required for conducting the synthesis.…”

Section: Example #1-coppermentioning

confidence: 90%

“…This finding is further supported by the changes in selectivity that occur when comparing the catalysts to the unpromoted catalyst at a similar conversion level. Table 2 shows that at the lower Cu promoter loading, the methane is slightly increased, C 5 + is slightly decreased [10]. However, increasing the Cu promoter loading further leads to a prohibitive increase in methane selectivity (21.6% versus 9.2%) and a precipitous drop in C 5 + selectivity (47.7% versus 81.6%) [10].…”

Section: Example #1-coppermentioning

confidence: 99%

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Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

Jacobs¹,

Ma²,

Davis³

2014

Catalysts

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This focused review article underscores how metal reduction promoters can impact deactivation phenomena associated with cobalt Fischer-Tropsch synthesis catalysts. Promoters can exacerbate sintering if the additional cobalt metal clusters, formed as a result of the promoting effect, are in close proximity at the nanoscale to other cobalt particles on the surface. Recent efforts have shown that when promoters are used to facilitate the reduction of small crystallites with the aim of increasing surface Co 0 site densities (e.g., in research catalysts), ultra-small crystallites (e.g., <2-4.4 nm) formed are more susceptible to oxidation at high conversion relative to larger ones. The choice of promoter is important, as certain metals (e.g., Au) that promote cobalt oxide reduction can separate from cobalt during oxidation-reduction (regeneration) cycles. Finally, some elements have been identified to promote reduction but either poison the surface of Co 0 (e.g., Cu), or produce excessive light gas selectivity (e.g., Cu and Pd, or Au at high loading). Computational studies indicate that certain promoters may inhibit polymeric C formation by hindering C-C coupling.

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Section: Resultsmentioning

confidence: 72%

Section: Example #1-coppermentioning

confidence: 64%

Section: Example #1-coppermentioning

confidence: 90%

Section: Example #1-coppermentioning

confidence: 99%

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Influence of Reduction Promoters on Stability of Cobalt/g-Alumina Fischer-Tropsch Synthesis Catalysts

Jacobs¹,

Ma²,

Davis³

2014

Catalysts

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“…However, promoters may not be redispersed as completely as the cobalt during repeated regeneration. Although traditional promoters, like Pt and Ru, appear to remain with the Co and maintain their effect, some promoters like Au tend to segregate and lose their promotion effect, as indicated by TPR peaks shifting to higher temperatures [384].…”

Section: Case Study: Cobalt Based Fischer-tropsch (Ft) Catalyst Regenmentioning

confidence: 99%

Heterogeneous Catalyst Deactivation and Regeneration: A Review

2015

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Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key features and considerations for each of these deactivation types is reviewed in detail with reference to the latest literature reports in these areas. Two case studies on the deactivation mechanisms of catalysts used for cobalt Fischer-Tropsch and selective catalytic reduction are considered to provide additional depth in the topics of sintering, coking, poisoning, and fouling. Regeneration considerations and options are also briefly discussed for each deactivation mechanism.

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