Fe catalysts for methane decomposition to produce hydrogen and carbon nano materials

[Display omitted] •Regardless preparation methods and Fe loading, Fe-Al2O3 catalysts showed the best CMD performance.•The selective formation of CNTs over Fe-Al2O3 catalysts is also speculated to be vital for their good CMD activity.•The graphite is proposed to be spurted out from an unstable over-s...

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Published in:Applied catalysis. B, Environmental Environmental, 2017-07, Vol.208, p.44-59
Main Authors: Zhou, Lu, Enakonda, Linga Reddy, Harb, Moussab, Saih, Youssef, Aguilar-Tapia, Antonio, Ould-Chikh, Samy, Hazemann, Jean-louis, Li, Jun, Wei, Nini, Gary, Daniel, Del-Gallo, Pascal, Basset, Jean-Marie
Format: Article
Language:English
Subjects:
Additives
Aluminum oxide
Carbon
Carbon dioxide
Catalysts
Chemical Sciences
Chemical synthesis
Contamination
Decomposition
Density functional theory
Deposition
Hydrogen
Iron carbides
Methane
Reaction mechanisms
Studies
Tubes
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Summary:[Display omitted] •Regardless preparation methods and Fe loading, Fe-Al2O3 catalysts showed the best CMD performance.•The selective formation of CNTs over Fe-Al2O3 catalysts is also speculated to be vital for their good CMD activity.•The graphite is proposed to be spurted out from an unstable over-stoichiometric iron carbide Fe3C1+x decomposition back to Fe3C and C.•At a low SV of 1.875L/gcath, this catalyst showed a stable methane conversion of c.a. 70% for as long as 400min. Conducting catalytic methane decomposition over Fe catalysts is a green and economic route to produce H2 without CO/CO2 contamination. Fused 65wt% and impregnated 20wt% Fe catalysts were synthesized with different additives to investigate their activity, whereas showing Fe-Al2O3 combination as the best catalyst. Al2O3 is speculated to expose more Fe0 for the selective deposition of carbon nano tubes (CNTs). A fused Fe (65wt%)-Al2O3 sample was further investigated by means of H2-TPR, in-situ XRD, HRTEM and XAS to conclude 750°C is the optimized temperature for H2 pre-reduction and reaction to obtain a high activity. Based on density functional theory (DFT) study, a reaction mechanism over Fe catalysts was proposed to explain the formation of graphite from unstable supersaturated iron carbides decomposition. A carbon deposition model was further proposed which explains the formation of different carbon nano materials.
ISSN:0926-3373
1873-3883
DOI:10.1016/j.apcatb.2017.02.052