The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions

M. I. Ariëns; V. Chlan; P. Novák; L. G.A. van de Water; A. I. Dugulan; E. Brück; E. J.M. Hensen

doi:10.1016/j.apcatb.2021.120465

The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions

M. I. Ariëns, V. Chlan, P. Novák, L. G.A. van de Water, A. I. Dugulan, E. Brück, E. J.M. Hensen^*

^*Corresponding author for this work

RST/Fundamental Aspects of Materials and Energy

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Abstract

Chromium promotion of iron oxide based water-gas shift (WGS) catalysts prepared via co-precipitation/calcination was investigated. Mössbauer spectroscopy and XRD evidence that chromium is incorporated in the calcined hematite (α-Fe₂O₃) precursor irrespective of the doping level (0−12 wt.%). CO-TPR shows chromium delays the reduction of hematite and the active magnetite (Fe₃O₄) phase. WGS activity was evaluated under realistic conditions for 4 days. Enhanced CO conversion was observed with increased chromium doping. Mössbauer spectra indicate that chromium incorporates into octahedral sites of magnetite and prevents reduction of Fe³⁺ to Fe²⁺ during formation of the active phase, leading to an increased Fe³⁺/Fe²⁺ ratio in octahedral sites. The higher Fe³⁺/Fe²⁺ ratio did not affect the high CO conversion associated with the structural stabilization mechanism of Cr-doping. Interpretation of the Mössbauer spectra was supported by computational modelling of various chromium and vacancy-doped magnetite structures. The bulk structure of an in situ prepared chromium-doped high-temperature WGS catalyst is best described as a partially oxidized chromium-doped magnetite phase. No surface effects of Cr-doping were found.

Original language	English
Article number	120465
Number of pages	14
Journal	Applied Catalysis B: Environmental
Volume	297
DOIs	https://doi.org/10.1016/j.apcatb.2021.120465
Publication status	Published - 2021

Keywords

Chromium
Iron oxide
Mössbauer spectroscopy
Promotion
Water-gas shift reaction

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10.1016/j.apcatb.2021.120465

1-s2.0-S0926337321005919-mainFinal published version, 9.04 MBLicence: CC BY

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title = "The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions",

abstract = "Chromium promotion of iron oxide based water-gas shift (WGS) catalysts prepared via co-precipitation/calcination was investigated. M{\"o}ssbauer spectroscopy and XRD evidence that chromium is incorporated in the calcined hematite (α-Fe2O3) precursor irrespective of the doping level (0−12 wt.%). CO-TPR shows chromium delays the reduction of hematite and the active magnetite (Fe3O4) phase. WGS activity was evaluated under realistic conditions for 4 days. Enhanced CO conversion was observed with increased chromium doping. M{\"o}ssbauer spectra indicate that chromium incorporates into octahedral sites of magnetite and prevents reduction of Fe3+ to Fe2+ during formation of the active phase, leading to an increased Fe3+/Fe2+ ratio in octahedral sites. The higher Fe3+/Fe2+ ratio did not affect the high CO conversion associated with the structural stabilization mechanism of Cr-doping. Interpretation of the M{\"o}ssbauer spectra was supported by computational modelling of various chromium and vacancy-doped magnetite structures. The bulk structure of an in situ prepared chromium-doped high-temperature WGS catalyst is best described as a partially oxidized chromium-doped magnetite phase. No surface effects of Cr-doping were found.",

keywords = "Chromium, Iron oxide, M{\"o}ssbauer spectroscopy, Promotion, Water-gas shift reaction",

author = "Ari{\"e}ns, {M. I.} and V. Chlan and P. Nov{\'a}k and {van de Water}, {L. G.A.} and Dugulan, {A. I.} and E. Br{\"u}ck and Hensen, {E. J.M.}",

year = "2021",

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T1 - The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions

AU - Ariëns, M. I.

AU - Chlan, V.

AU - Novák, P.

AU - van de Water, L. G.A.

AU - Dugulan, A. I.

AU - Brück, E.

AU - Hensen, E. J.M.

PY - 2021

Y1 - 2021

N2 - Chromium promotion of iron oxide based water-gas shift (WGS) catalysts prepared via co-precipitation/calcination was investigated. Mössbauer spectroscopy and XRD evidence that chromium is incorporated in the calcined hematite (α-Fe2O3) precursor irrespective of the doping level (0−12 wt.%). CO-TPR shows chromium delays the reduction of hematite and the active magnetite (Fe3O4) phase. WGS activity was evaluated under realistic conditions for 4 days. Enhanced CO conversion was observed with increased chromium doping. Mössbauer spectra indicate that chromium incorporates into octahedral sites of magnetite and prevents reduction of Fe3+ to Fe2+ during formation of the active phase, leading to an increased Fe3+/Fe2+ ratio in octahedral sites. The higher Fe3+/Fe2+ ratio did not affect the high CO conversion associated with the structural stabilization mechanism of Cr-doping. Interpretation of the Mössbauer spectra was supported by computational modelling of various chromium and vacancy-doped magnetite structures. The bulk structure of an in situ prepared chromium-doped high-temperature WGS catalyst is best described as a partially oxidized chromium-doped magnetite phase. No surface effects of Cr-doping were found.

AB - Chromium promotion of iron oxide based water-gas shift (WGS) catalysts prepared via co-precipitation/calcination was investigated. Mössbauer spectroscopy and XRD evidence that chromium is incorporated in the calcined hematite (α-Fe2O3) precursor irrespective of the doping level (0−12 wt.%). CO-TPR shows chromium delays the reduction of hematite and the active magnetite (Fe3O4) phase. WGS activity was evaluated under realistic conditions for 4 days. Enhanced CO conversion was observed with increased chromium doping. Mössbauer spectra indicate that chromium incorporates into octahedral sites of magnetite and prevents reduction of Fe3+ to Fe2+ during formation of the active phase, leading to an increased Fe3+/Fe2+ ratio in octahedral sites. The higher Fe3+/Fe2+ ratio did not affect the high CO conversion associated with the structural stabilization mechanism of Cr-doping. Interpretation of the Mössbauer spectra was supported by computational modelling of various chromium and vacancy-doped magnetite structures. The bulk structure of an in situ prepared chromium-doped high-temperature WGS catalyst is best described as a partially oxidized chromium-doped magnetite phase. No surface effects of Cr-doping were found.

KW - Chromium

KW - Iron oxide

KW - Mössbauer spectroscopy

KW - Promotion

KW - Water-gas shift reaction

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ER -

The role of chromium in iron-based high-temperature water-gas shift catalysts under industrial conditions

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