Carbon deposition over Fe, Ni, and Co foils from CO-H2-CH4-CO2-H2O, CO-CO2, CH4-H2, and CO-H2-H2O gas mixtures: II. Kinetics

Jablonski, G. A.; Geurts, F. W. A. H.; Sacco, Albert

doi:10.1016/0008-6223(92)90112-a

Cited by 35 publications

(19 citation statements)

References 18 publications

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“…The amount of deposition on these foils is comparable. It is known that Fe and Co are also catalytically active toward carbon deposition during the thermal stressing of hydrocarbons. ,− Chambers et al studied the cobalt−copper binary system and observed that increasing the Co content decreases the carbon deposition during ethylene thermal stressing.…”

Section: Resultsmentioning

confidence: 99%

Analysis of Carboneceous Deposits from Thermal Stressing of a JP-8 Fuel on Superalloy Foils in a Flow Reactor

Altın

Eser

2000

Ind. Eng. Chem. Res.

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A flow reactor study was carried out to investigate the carbon deposition on nickel-, cobalt-, molybdenum-, and iron-based alloy foils during thermal stressing of a JP-8 fuel at 500 °C wall temperature and 34 atm (500 psig), for 5 h at a fuel flow rate of 4 mL/min. Temperature-programmed oxidation (TPO) analysis and SEM examination showed that the amount and the nature of the carbonaceous deposits on the foils depend strongly on the chemical composition of the foil surface. The amount of carbon deposited on metal foils decreased in the order Inconel 600 > Havar > Fecralloy > Waspaloy > Hastelloy-C > MoRe > Inconel 718. The presence of minor components, such as Ti, Al, and Nb, in the alloys appears to be responsible for reducing carbon deposition from jet fuel thermal stressing. This effect can be attributed to the formation of a passive layer on alloy surfaces that limits the access of deposit precursors to base metals, Ni, Fe, and Co, that catalyze deposit formation.

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Section: Resultsmentioning

confidence: 99%

Analysis of Carboneceous Deposits from Thermal Stressing of a JP-8 Fuel on Superalloy Foils in a Flow Reactor

Altın

Eser

2000

Ind. Eng. Chem. Res.

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“…Carbon formation rates depend linearly on the carbon activity ( a C ) for these equilibrated mixtures, , consistent with a diffusion-limited filament growth mechanism. A few studies have addressed the formation rates and morphology of carbon filaments during CO–H 2 –H 2 O–CO 2 –CH 4 reactions ,− but without accurate mechanism-based frameworks, which are required to relate the prevalent carbon activity at catalytic surfaces to the dynamics of filament formation under different reaction conditions. The information available about the effects of Ni crystallite size on growth rates and morphology of carbon deposits remains largely anecdotal. , Moreover, the effects of H 2 on carbon deposition rates remain contradictory, with some studies , reporting that H 2 increases carbon formation rates and others , demonstrating the opposite trend.…”

Section: Introductionmentioning

confidence: 99%

“…A few studies have addressed the formation rates and morphology of carbon filaments during CO–H 2 –H 2 O–CO 2 –CH 4 reactions ,− but without accurate mechanism-based frameworks, which are required to relate the prevalent carbon activity at catalytic surfaces to the dynamics of filament formation under different reaction conditions. The information available about the effects of Ni crystallite size on growth rates and morphology of carbon deposits remains largely anecdotal. , Moreover, the effects of H 2 on carbon deposition rates remain contradictory, with some studies , reporting that H 2 increases carbon formation rates and others , demonstrating the opposite trend. The effect of H 2 on the thermodynamic carbon activity prevalent during reactions of CO–H 2 –H 2 O–CO 2 –CH 4 mixtures remains largely unexplored at this time.…”

Section: Introductionmentioning

confidence: 99%

Dynamics and Mechanism of Carbon Filament Formation during Methane Reforming on Supported Nickel Clusters

et al. 2020

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CH 4 −CO 2 and CH 4 −H 2 O reforming on Ni-based catalysts can lead to the undesired formation of carbonaceous residues. The dynamics of the formation of carbon filaments and encapsulating layers on dispersed Ni nanoparticles (5−11 nm diameter) are determined here using an inertial microbalance to measure mass changes and mass spectrometry to concurrently assess turnover rates under conditions of reforming practice (800− 1000 K). The morphology and rate of formation of carbonaceous species were controlled by a ratio of pressures (χ = P CH 4 P CO /P CO 2 or ψ = P CH 4 P H 2 /P H 2 O ), which are proportional to each other through the equilibration of water-gas shift) that uniquely determines the thermodynamic activity of carbon at the metal surface ((a C* ) s ) and the thermodynamic driving force for carbon diffusion and filament formation, based on a reaction-transport model derived from the elementary steps that mediate CH 4 reforming. Each sample exhibited three distinct kinetic regimes for carbon formation, which evolved with increasing χ values from undetectable carbon deposition (I) to a constant rate of carbon filament growth without detectable changes in CH 4 reforming rates (II) and ultimately to the formation of carbon overlayers with a concurrent decrease in CH 4 reforming and carbon formation rates (III). Rates of filament growth in regime II were proportional to χ or ψ values, consistent with a filament growth mechanism limited by carbon diffusion. Such carbon filaments were similar in diameter to the attached Ni nanoparticles. In regime III, the high prevalent carbon activities led to the simultaneous nucleation of several carbon patches, thus precluding the directional diffusion imposed by a single filament and leading to the encapsulation and loss of accessible surface for CH 4 turnovers. Filaments formed in regime II were removed when placed under the conditions of regime I via the microscopic reverse of their formation processes. Threshold carbon activities required for the incipient formation of filaments are higher and filament formation rates are lower (for a given χ or ψ) on smaller nanoparticles because of the lower stability (higher thermodynamic carbon activity) of filaments with smaller diameters. Carbon deposition rates decreased with increasing temperature (for a given χ or ψ) because of a corresponding decrease in the lumped kinetic and thermodynamic parameters that relate the surface carbon activity to χ or ψ. The formalism used to describe carbon formation rates, in this study for CH 4 reforming rates far from equilibrium and for carbon formation and removal rates that do not disturb the carbon activity set by CH 4 reforming turnovers at steady-state, also informs the testing of these assumptions while providing also a framework for the rigorous extension of these reaction-diffusion constructs to more practical conditions, for which these assumptions may no longer apply.

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“…Among the different metals commonly used in CNF and H 2 production, Ni-based supported catalysts are of special interest because they show good activity at relatively moderate temperatures [18,[22][23][24][25][26]. Indeed, the decomposition temperature of methane (870-970 K) with these catalysts is about 300 K lower than that with Fe-based catalysts.…”

Section: Introductionmentioning

confidence: 99%

Development of Ni–Cu–Mg–Al catalysts for the synthesis of carbon nanofibers by catalytic decomposition of methane

Dussault

Dupin

Guímon

et al. 2007

Journal of Catalysis

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Carbon deposition over Fe, Ni, and Co foils from CO-H2-CH4-CO2-H2O, CO-CO2, CH4-H2, and CO-H2-H2O gas mixtures: II. Kinetics

Cited by 35 publications

References 18 publications

Analysis of Carboneceous Deposits from Thermal Stressing of a JP-8 Fuel on Superalloy Foils in a Flow Reactor

Analysis of Carboneceous Deposits from Thermal Stressing of a JP-8 Fuel on Superalloy Foils in a Flow Reactor

Dynamics and Mechanism of Carbon Filament Formation during Methane Reforming on Supported Nickel Clusters

Development of Ni–Cu–Mg–Al catalysts for the synthesis of carbon nanofibers by catalytic decomposition of methane

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