A model study of the hydrogenation of CO over polycrystalline iron

Krebs, H.; Bonzel, H.P.; Gafner, G.

doi:10.1016/0039-6028(79)90579-x

Cited by 147 publications

(54 citation statements)

References 21 publications

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“…a) Reaction conditions for Fischer-Tropsch catalysis in the solar nebula, a circumplanetary subnebula, cometary impact vapor clouds, and the atmospheric re-entry of vapor condensate due to asteroidal impacts on early Earth. b) The range of pressure and H 2 /CO ratio of the previous experimental studies (broken lines) (Krebs et al 1979;Goodman et al 1980;Sekine et al 2005) and that of this study for iron and nickel catalysts (solid lines). et al (2005) obtained the methane formation rate for iron catalyst at H 2 /CO = 1000 and P = 2.0 × 10 −2 -5.3 × 10 −1 bars.…”

Section: Conditionsmentioning

confidence: 84%

“…However, the relevant reaction temperature ranges only from 400 to 700 K (e.g., Krebs et al 1979;Sekine et al 2005), but pressure and the H 2 /CO ratio vary widely in nebulae and impact vapor. Thus, pressure and the H 2 /CO ratio become especially important in this study.…”

Section: Conditionsmentioning

confidence: 99%

“…Figure 1b shows the range of pressure and H 2 /CO ratio, for which the methane formation rate has been experimentally obtained for iron and nickel catalysts in the previous studies. In industrial chemistry, methane formation rates have been investigated experimentally at pressures higher than 1 bar and at H 2 /CO = 4-100 for iron catalyst (Krebs et al 1979) and at pressures higher than 1.3 × 10 −3 bar and at H 2 /CO = 4 for nickel catalyst (Goodman et al 1980). More recently, Sekine Fig.…”

Section: Conditionsmentioning

confidence: 99%

“…However, today's available quantitative data of Fischer-Tropsch catalysis have been obtained mainly in industrial chemistry (e.g., Vannice 1975;Krebs et al 1979;Goodman et al 1980). Since the productivities of the hydrocarbons are not very good at lower pressures, the laboratory data under conditions relevant to planetary processes have not been reported in industrial chemistry.…”

Section: Introductionmentioning

confidence: 99%

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An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry

Sekine

Sugita

Shido

et al. 2006

Meteoritics &Amp; Planetary Science

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Abstract-Fischer-Tropsch catalysis, by which CO and H 2 are converted to CH 4 on the surface of transition metals, has been considered to be one of the most important chemical reactions in many planetary processes, such as the formation of the solar and circumplanetary nebulae, the expansion of vapor clouds induced by cometary impacts, and the atmospheric re-entry of vapor condensate due to asteroidal impacts. However, few quantitative experimental studies have been conducted for the catalytic reaction under conditions relevant to these planetary processes. In this study, we conduct Fischer-Tropsch catalytic experiments at low pressures (1.3 × 10 −4 bar ≤ P ≤ 5.3 × 10 −1 bar) over a wide range of H 2 /CO ratios (0.25-1000) using pure iron, pure nickel, and iron-nickel alloys. We analyze what gas species are produced and measure the CH 4 formation rate. Our results indicate that the CH 4 formation rate for iron catalysts strongly depends on both pressure and the H 2 /CO ratio, and that nickel is a more efficient catalyst at lower pressures and lower H 2 /CO ratios. This difference in catalytic properties between iron and nickel may come from the reaction steps concerning disproportionation of CO, hydrogenation of surface carbon, and the poisoning of the catalyst. These results suggest that nickel is important in the atmospheric re-entry of impact condensate, while iron is efficient in circumplanetary subnebulae. Our results also indicate that previous numerical models of iron catalysis based on experimental data at 1 bar considerably overestimate CH 4 formation efficiency at lower pressures, such as the solar nebula and the atmospheric re-entry of impact condensate.

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Section: Conditionsmentioning

confidence: 84%

Section: Conditionsmentioning

confidence: 99%

Section: Conditionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry

Sekine

Sugita

Shido

et al. 2006

Meteoritics &Amp; Planetary Science

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“…Then, radiative cooling would act as the dominant cooling mechanism. We speculate that when the cooling gas experiences the catalytically optimal temperatures (∼400-700 K: Krebs et al 1979;Sekine et al 2005), long timescales of radiative cooling would allow heterogeneous reactions to proceed efficiently (Kress & McKay 2004). The equilibrium calculation implies that the heterogeneous reactions could reduce the CO/N 2 and H 2 /N 2 ratios to ∼10 −4 and ∼10 −3 , respectively ( Figure 5).…”

Section: By-products Of Impact Shock Chemistrymentioning

confidence: 99%

OXIDIZING PROTO-ATMOSPHERE ON TITAN: CONSTRAINT FROM N₂FORMATION BY IMPACT SHOCK

Ishimaru¹,

Sekine²,

Matsui³

et al. 2011

ApJ

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Titan is the only satellite that possesses a thick atmosphere, composed mainly of N 2 and CH 4 . However, its origin and evolution remain largely unknown. Knowledge of the acquirement of a N 2 atmosphere on Titan would provide insights into nitrogen evolution in planetary atmospheres as well as the formation of satellite systems around gas giants. Previous studies have proposed that the atmospheric N 2 would have been converted from NH 3 via shock heating by accreting satellitesimals in the highly reducing proto-atmosphere composed of NH 3 and CH 4 . Nevertheless, the validity of this mechanism strongly depends on both the composition of the proto-atmosphere and kinetics of shock chemistry. Here, we show that a CO 2 -rich oxidizing proto-atmosphere is necessary to form N 2 from NH 3 efficiently by atmospheric shock heating. Efficient shock production of N 2 is inhibited in a reducing protoatmosphere composed of NH 3 and CH 4 , because CH 4 plays as the coolant gas owing to its large heat capacity. Our calculations show that the amount of N 2 produced in a CO 2 -rich proto-atmosphere could have reached ∼20 times that on the present Titan. Although further quantitative analysis are required (especially, the occurrence of catalytic reactions), our results imply that the chemical composition of satellitesimals that formed the Saturnian system is required to be oxidizing if the current atmospheric N 2 is derived from the shock heating in the proto-atmosphere during accretion. This supports the formation of regular satellites in an actively supplied circumplanetary disk using CO 2 -rich materials originated from the solar nebula at the final stage of gas giant formation.

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Model Studies of Surface Catalyzed Reactions

Sault

Goodman

1989

Advances in Chemical Physics

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A model study of the hydrogenation of CO over polycrystalline iron

Cited by 147 publications

References 21 publications

An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry

An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry

OXIDIZING PROTO-ATMOSPHERE ON TITAN: CONSTRAINT FROM N₂FORMATION BY IMPACT SHOCK

Model Studies of Surface Catalyzed Reactions

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A model study of the hydrogenation of CO over polycrystalline iron

Cited by 147 publications

References 21 publications

An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry

An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry

OXIDIZING PROTO-ATMOSPHERE ON TITAN: CONSTRAINT FROM N2FORMATION BY IMPACT SHOCK

Model Studies of Surface Catalyzed Reactions

Contact Info

Product

Resources

About

OXIDIZING PROTO-ATMOSPHERE ON TITAN: CONSTRAINT FROM N₂FORMATION BY IMPACT SHOCK