Fischer–Tropsch synthesis: effect of water on the deactivation of Pt promoted Co/Al2O3 catalysts

Li, Jinlin; Zhan, Xiaodong; Zhang, Yongqing; Jacobs, Gary; Das, Tapan K.; Davis, Burtron H.

doi:10.1016/s0926-860x(01)00977-2

Cited by 162 publications

(101 citation statements)

References 16 publications

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“…At high conversions high partial pressures of H2O may oxidize small cobalt crystallites and promote aluminate formation thus enhancing WGS activity as shown by a significant CO2 make. Similar results were found for a Pt promoted catalyst [54].…”

Section: Deactivation By Re-oxidationsupporting

confidence: 86%

Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts—A Mini-Review

2015

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Deactivation of commercially relevant cobalt catalysts for Low Temperature Fischer-Tropsch (LTFT) synthesis is discussed with a focus on the two main long-term deactivation mechanisms proposed: Carbon deposits covering the catalytic surface and re-oxidation of the cobalt metal. There is a great variety in commercial, demonstration or pilot LTFT operations in terms of reactor systems employed, catalyst formulations and process conditions. Lack of sufficient data makes it difficult to correlate the deactivation mechanism with the actual process and catalyst design. It is well known that long term catalyst deactivation is sensitive to the conditions the actual catalyst experiences in the reactor. Therefore, great care should be taken during start-up, shutdown and upsets to monitor and control process variables such as reactant concentrations, pressure and temperature which greatly affect deactivation mechanism and rate. Nevertheless, evidence so far shows that carbon deposition is the main long-term deactivation mechanism for most LTFT operations. It is intriguing that some reports indicate a low deactivation rate for multi-channel micro-reactors. In situ rejuvenation and regeneration of Co catalysts are economically necessary for extending their life to several years. The review covers information from open sources, but with a particular focus on patent literature.

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Section: Deactivation By Re-oxidationsupporting

confidence: 86%

Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts—A Mini-Review

2015

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“…Although H 2 O co-feeding can lead to improvements in activity and selectivity for certain cobalt catalysts [48], when a Pt promoter was utilized to facilitate the reduction of Co oxides in a 15%Co/Al 2 O 3 catalyst (average cluster diameter = 5.6 nm), at 28 vol.% added H 2 O the catalyst underwent significant cobalt aluminate formation, as demonstrated in Figure 10 (left) and (right) [49,50] along with catastrophic deactivation (75% drop in X CO ). An unpromoted 25%Co/Al 2 O 3 catalyst with larger cluster size (11.8 nm average diameter) [40] was more resistant to this phenomenon.…”

Section: Sintering and Co Support Compound Formation During Initial Dmentioning

confidence: 99%

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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“…Li et al [15] investigated the effect of water for a platinum-promoted Co/c-Al 2 O 3 catalyst during FischerTropsch synthesis in a continuously stirred tank reactor. The catalyst lost activity in the presence of water, and it was found that small quantities of water (3-25 vol.%) led to mild reversible deactivation, whereas large amounts of water (>28 vol.%) deactivated the catalyst permanently.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Water on the Activity and Selectivity for γ-Alumina Supported Cobalt Fischer–Tropsch Catalysts with Different Pore Sizes

et al. 2006

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The effect of water on the activity and selectivity for a series of c-Al 2 O 3 supported cobalt Fischer-Tropsch catalysts has been studied in an isothermal fixed-bed reactor at T=483 K, P=20 bar, and H 2 /CO=2.1. The catalysts were produced applying incipient wetness impregnation and consisted of 20 wt.% cobalt and 0.5 wt.% rhenium deposited on c-Al 2 O 3 supports with different pore characteristics. For the narrow-pore catalysts, addition of water corresponding to an inlet partial pressure ratio of P H2 O/P H2 =0.4 reduced the reaction rates. In contrast, for a catalyst with larger pores the same water pressure increased the reaction rates. For all catalysts, water amounts equal to P H2 O/P H2 =0.7 at the reactor inlet suppressed the reaction rates and led to permanent deactivation. The addition of water increased the C 5+ selectivity and decreased the CH 4 selectivity for all catalysts. The pore characteristics seem to determine the effect of water on the rates.

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Fischer–Tropsch synthesis: effect of water on the deactivation of Pt promoted Co/Al2O3 catalysts

Cited by 162 publications

References 16 publications

Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts—A Mini-Review

Deactivation and Regeneration of Commercial Type Fischer-Tropsch Co-Catalysts—A Mini-Review

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

The Effect of Water on the Activity and Selectivity for γ-Alumina Supported Cobalt Fischer–Tropsch Catalysts with Different Pore Sizes

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