Study of the deactivation mechanism of Al2O3-supported cobalt Fischer-Tropsch catalysts

Schanke, Dag; Hilmen, Anne-Mette; Bergene, Edvard; Kinnari, Keijo J.; Rytter, Erling; �dnanes, E.; Holmén, Anders

doi:10.1007/bf00806876

Cited by 151 publications

(70 citation statements)

References 18 publications

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“…Adding 20-28% steam to 50% syngas in the feed of a lab-scale fixed-bed reactor resulted in significant deactivation due to oxidation of highly dispersed cobalt crystals and surface cobalt atoms [53]. Although these experiments clearly show oxidation of cobalt, the conditions represent very high conversion levels (> 80%).…”

Section: Deactivation By Re-oxidationmentioning

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-oxidationmentioning

confidence: 86%

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

2015

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“…Oxidation of metallic cobalt in cobaltbased Fischer-Tropsch synthesis has been long debated in the open literature [28,60,[146][147][148][149][150][151][152]. However, it has been shown [28,151,152] that oxidation of the catalyst with water should not occur under realistic Fischer-Tropsch conditions if the metallic cobalt crystallites are larger than 4-5 nm (it should be pointed out here that even larger crystallites are required in the reduced catalyst to obtain the highest intrinsic activitysee Fig.…”

Section: Inherent Catalyst Deactivation In the Fischertropsch Synthesismentioning

confidence: 99%

Fischer‐Tropsch Catalysts for the Biomass‐to‐Liquid (BTL)‐Process

2008

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The Fischer-Tropsch synthesis is at the heart of the Biomass-to-Liquids (BTL) process. Feasibility studies published in open literature typically consider cobaltbased catalysts for the Fischer-Tropsch synthesis. Here, we present an overview on the history and development up until the present for both cobalt-and ironbased Fischer-Tropsch catalysts. The role of the support material and various other additives to the catalyst formulation are discussed in detail with regard to activity, catalyst deactivation, and selectivity. Tentative explanations for e.g. the observed size dependency in cobalt-based catalysts and phase transformations in iron-based Fischer-Tropsch catalysts are offered. The productivity of cobalt-based catalysts at high conversion level is currently higher than that of iron-based catalysts. Nevertheless, it is argued that iron-based catalysts may be an attractive option for the BTL-process, since it is much cheaper, impacting on the cost of the process due to inevitable process set-ups in industrial operation. Improvement of current iron-based catalysts is however desired.

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“…Schanke et al [3,4] found that the presence of large amounts of water suppressed the activity of unpromoted as well as promoted cobalt supported on c-Al 2 O 3 . From X-ray photoelectron spectra, Schanke et al [3,4] concluded that reoxidation of surface cobalt atoms or highly dispersed cobalt phases, and not bulk cobalt oxidation, was responsible for the loss in activity. Hilmen et al [5][6][7] also observed a loss in activity when water was introduced to unpromoted and promoted cobalt deposited on c-Al 2 O 3 .…”

Section: Introductionmentioning

confidence: 98%

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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Study of the deactivation mechanism of Al2O3-supported cobalt Fischer-Tropsch catalysts

Cited by 151 publications

References 18 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

Fischer‐Tropsch Catalysts for the Biomass‐to‐Liquid (BTL)‐Process

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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