Fischer–Tropsch synthesis: Comparisons between Pt and Ag promoted Co/Al2O3 catalysts for reducibility, local atomic structure, catalytic activity, and oxidation–reduction (OR) cycles

Jermwongratanachai, Thani; Jacobs, Gary; Ma, Wanhong; Shafer, Wilson D.; Gnanamani, Muthu Kumaran; Gao, Pei; Kitiyanan, Boonyarach; Davis, Burtron H.; Klettlinger, Jennifer L.S.; Yen, Chia H.; Cronauer, Donald C.; Kropf, A. Jeremy; Marshall, Christopher L.

doi:10.1016/j.apcata.2013.05.040

Cited by 65 publications

(36 citation statements)

References 32 publications

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“…For all Pt-promoted catalysts, slightly lower C 5 + selectivities were observed compared to the unpromoted catalyst. With the Ag-promoted catalysts, C 1 and C 5 + selectivities were slightly improved at all loadings [28]. Thus, the presence of a weakly hydrogenating metal [29], Ag, did not adversely affect selectivity to a significant degree, even when excessive amounts of promoter were added [28].…”

Section: Example #4-impact Of Loading For Pt and Ag Promoted Catalystsmentioning

confidence: 77%

“…A single low distance peak indicates primarily Pt-Co coordination, with no visible Pt-Pt coordination being evident. As shown in Table 7, as loading was increased for the Pt promoted catalyst, a slight negative impact on selectivity occurred, with a slight decrease in C 5 + and a slight increase in the WGS rate [28]. For all Pt-promoted catalysts, slightly lower C 5 + selectivities were observed compared to the unpromoted catalyst.…”

Section: Example #4-impact Of Loading For Pt and Ag Promoted Catalystsmentioning

confidence: 92%

“…Figure 3 (left) compares the Ag K-edge EXAFS Fourier transform magnitude spectra of Ag-promoted 25%Co/Al 2 O 3 catalysts as a function of Ag loading. While a lower distance peak for Ag-Co coordination is suggested (and confirmed by EXAFS fittings), with increasing loading of Ag, the general trend in EXAFS fittings for Ag-promoted 25%Co/Al 2 O 3 catalysts was increasing Ag-Ag coordination (higher distance peak), such that the N Ag-Co /N Ag-Ag ratio decreased from 0.59 at 0.276%Ag loading to 0.16 at 2.76%Ag loading [28]. Figure 3 (right) compares the Pt L III -edge EXAFS Fourier transform magnitude spectra of Pt-promoted 25%Co/Al 2 O 3 catalysts.…”

Section: Example #4-impact Of Loading For Pt and Ag Promoted Catalystsmentioning

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: Example #4-impact Of Loading For Pt and Ag Promoted Catalystsmentioning

confidence: 77%

Section: Example #4-impact Of Loading For Pt and Ag Promoted Catalystsmentioning

confidence: 92%

Section: Example #4-impact Of Loading For Pt and Ag Promoted Catalystsmentioning

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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“…Ag is a relatively inert metal and is known to reduce at low temperature. It has been used recently to facilitate reduction of Co/Al 2 O 3 catalysts for Fischer-Tropsch synthesis [22,23]. Because the reduction of Pt oxide is facilitated by addition of Ag dopant, the results suggest that Pt clusters are likely in contact with, or in close proximity to, the Ag dopant.…”

Section: Resultsmentioning

confidence: 87%

Mitigation of Methane Selectivity on Pt/KL-Zeolite Aromatization Catalysts by Ag Promotion

et al. 2016

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Silver addition, in low amounts (0.0054 or 0.013 %), to a 1 %Pt/KL catalysts prepared by a sequential CVD procedure using acetylacetonates resulted in improved benzene selectivity at similar conversion levels compared to the undoped 1 %Pt/KL CVD catalyst. Both hydrogenolysis and aromatization require an ensemble of atoms to constitute the active site, but hydrogenolysis is more structure sensitive. Silver, which is a relatively inert metal catalyst, blocks a fraction of Pt surface sites, lowering the overall n-hexane rate. When added in low levels, silver disrupts to a greater degree the Pt ensembles responsible for hydrogenolysis relative to those required for aromatization. This was confirmed by DRIFTS of adsorbed CO measurements, which showed that higher wavenumber bands attributed to larger Pt ensembles were suppressed to a greater extent relative to lower wavenumber bands (i.e., arising from smaller ensembles). Graphical AbstractKeywords Platinum (Pt) Á Pt/KL Á L-Zeolite (LTL) Á Silver (Ag) Á Hydrogenolysis Á Aromatization

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“…The first peak, situated at a temperature around 300 °C, is ascribed to the reduction of Co 3+ to Co 2+ (i.e. Co 3 O 4 to CoO) [8,12,14,48]. The second peak, situated at ca.…”

Section: Physicochemical Properties Of the Catalystsmentioning

confidence: 99%

Fischer–Tropsch Synthesis Over Zr-Promoted Co/γ-Al2O3 Catalysts

Barrientos

Garcilaso²,

Venezia

et al. 2017

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Fischer–Tropsch synthesis: Comparisons between Pt and Ag promoted Co/Al2O3 catalysts for reducibility, local atomic structure, catalytic activity, and oxidation–reduction (OR) cycles

Cited by 65 publications

References 32 publications

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

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

Mitigation of Methane Selectivity on Pt/KL-Zeolite Aromatization Catalysts by Ag Promotion

Fischer–Tropsch Synthesis Over Zr-Promoted Co/γ-Al2O3 Catalysts

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