Controlling the stability of a Fe–Ni reforming catalyst: Structural organization of the active components

[Display omitted] •Enhanced control of the stability of carbon resistant Fe–Ni/MgAl2O4.•Formation of a core shell alloy with Fe–Ni in the core and Fe–Ni–Pd in the shell.•Catalyst with Ni:Pd molar ratio of 75:1 showed the best performance.•The addition of Pd to Fe–Ni reduces the tendency of Fe to seg...

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Vydáno v:Applied catalysis. B, Environmental Ročník 209; s. 405 - 416
Hlavní autoři: Theofanidis, Stavros Alexandros, Galvita, Vladimir V., Sabbe, Maarten, Poelman, Hilde, Detavernier, Christophe, Marin, Guy B.
Médium: Journal Article
Jazyk:angličtina
Vydáno: Amsterdam Elsevier B.V 15.07.2017
Elsevier BV
Témata:
Bimetals
Carbon dioxide
Catalyst stability
Catalysts
Control stability
Deactivation
Fe–Ni alloy
In situ XRD
Iron
Methane
Methane reforming
Nickel
Oxidation
Reduction
Reforming
Sintering
Surface layers
Synthesis gas
Temperature effects
X-ray diffraction
Catalyst stability
Methane reforming
Synthesis gas
In situ XRD
Fe–Ni alloy
ISSN:0926-3373, 1873-3883
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Shrnutí:[Display omitted] •Enhanced control of the stability of carbon resistant Fe–Ni/MgAl2O4.•Formation of a core shell alloy with Fe–Ni in the core and Fe–Ni–Pd in the shell.•Catalyst with Ni:Pd molar ratio of 75:1 showed the best performance.•The addition of Pd to Fe–Ni reduces the tendency of Fe to segregate from the alloy. Fe–Ni catalysts present high activity in dry reforming of methane, with high carbon resistance, but suffer from deactivation via sintering and Fe segregation. Enhanced control of the stability and activity of Fe–Ni/MgAl2O4 was achieved by means of Pd addition. The evolution of the catalyst structure during H2 Temperature Programmed Reduction (TPR) and CO2 Temperature Programmed Oxidation (TPO) was investigated using time-resolved in situ X-ray diffraction (XRD). During reduction of Fe–Ni–Pd supported on MgAl2O4, a core shell alloy forms at the surface, where Fe–Ni is in the core and Fe–Ni–Pd in the shell. A 0.2wt% Pd loading or Ni:Pd molar ratio as high as 75:1 showed the best performance in terms of both activity and stability of the catalyst at 1023K and total pressure of 101.3kPa. Experimental results and DFT calculations showed that Pd addition to bimetallic Fe–Ni reduces the tendency of Fe to segregate to the surface of the alloy particles under methane dry reforming (DRM) conditions, due to the formation of a thin Fe–Ni–Pd surface layer. The latter acts as a barrier for Fe segregation from the core. Segregation of Fe from the trimetallic shell still occurs, but to a lesser extent as the Fe concentration is lower. This Ni:Pd molar ratio is capable of controlling the carbon formation and hence ensure high catalyst activity of 24.8mmols−1gmetals−1 after 21h time-on-stream.
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ISSN:0926-3373
1873-3883
DOI:10.1016/j.apcatb.2017.03.025