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)

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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 - 15 Nov 2021

Bibliographical note

Funding Information:
This publication is part of the project Application of advanced combined in-situ Mössbauer/IR/GC characterisation under industrially relevant conditions to underpin and accelerate development of improved Fe-based catalysts with project number 731.015.419 of the research programme LIFT, which is (partly) financed by the Dutch Research Council (NWO) . The authors would like to thank Arno van Hoof for the TEM measurements and Freddy Oropeza for his assistance and advice on the XPS measurements. Deborah Dodds for her advice and training in catalyst preparation and Michel Steenvoorden for his help with the Mössbauer spectroscopy setup.

Publisher Copyright:
© 2021 The Author(s)

Keywords

Chromium
Iron oxide
Mössbauer spectroscopy
Promotion
Water-gas shift reaction

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

note = "Funding Information: This publication is part of the project Application of advanced combined in-situ M{\"o}ssbauer/IR/GC characterisation under industrially relevant conditions to underpin and accelerate development of improved Fe-based catalysts with project number 731.015.419 of the research programme LIFT, which is (partly) financed by the Dutch Research Council (NWO) . The authors would like to thank Arno van Hoof for the TEM measurements and Freddy Oropeza for his assistance and advice on the XPS measurements. Deborah Dodds for her advice and training in catalyst preparation and Michel Steenvoorden for his help with the M{\"o}ssbauer spectroscopy setup. Publisher Copyright: {\textcopyright} 2021 The Author(s)",

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doi = "10.1016/j.apcatb.2021.120465",

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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.

N1 - Funding Information: This publication is part of the project Application of advanced combined in-situ Mössbauer/IR/GC characterisation under industrially relevant conditions to underpin and accelerate development of improved Fe-based catalysts with project number 731.015.419 of the research programme LIFT, which is (partly) financed by the Dutch Research Council (NWO) . The authors would like to thank Arno van Hoof for the TEM measurements and Freddy Oropeza for his assistance and advice on the XPS measurements. Deborah Dodds for her advice and training in catalyst preparation and Michel Steenvoorden for his help with the Mössbauer spectroscopy setup. Publisher Copyright: © 2021 The Author(s)

PY - 2021/11/15

Y1 - 2021/11/15

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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U2 - 10.1016/j.apcatb.2021.120465

DO - 10.1016/j.apcatb.2021.120465

M3 - Article

AN - SCOPUS:85109081027

SN - 0926-3373

VL - 297

JO - Applied Catalysis. B, Environmental

JF - Applied Catalysis. B, Environmental

M1 - 120465

ER -

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

Abstract

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