The role of Cr<sub>2</sub>O<sub>3</sub> in Catalyst for Water‐Gas Shift Reaction

Domka, F.; Laniecki, M.

doi:10.1002/zaac.19774350136

Cited by 13 publications

(3 citation statements)

References 8 publications

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“…Although Cr is generally thought of as a structural stabilizer that retards sintering of iron oxide, , the ability of Cr to shuttle between Cr 6+ and Cr 3+ valence states was considered as proof that Cr can facilitate the HT-WGS redox cycle . The present in situ XANES redox study demonstrates that the initial Cr 6+ is indeed reduced to Cr 3+ during WGS/RWGS reaction conditions, but neither CO 2 or H 2 O possesses enough oxidizing potential to oxidize Cr 3+ back to Cr 6+ .…”

Section: Discussionmentioning

confidence: 76%

Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper

Zhu,

Rocha,

Lunkenbein

et al. 2016

ACS Catal.

106

118

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The Cr and Cu promotion mechanisms of high temperature water–gas shift (HT-WGS) iron oxide catalysts, synthesized by coprecipitation, were investigated as a function of reaction conditions. XRD and in situ Raman characterization showed that the initial calcined catalysts consisted of the Fe₂O₃ (hematite) bulk phase and transformed to the Fe₃O₄ (magnetite) phase during the HT-WGS reactions. In situ NAP-XPS and HS-LEIS surface analysis revealed that Cr was surface enriched as Cr⁶⁺ for the initial catalyst and reduced to Cr³⁺ during the HT-WGS reactions, with the Cr³⁺ dissolving into the bulk iron oxide lattice forming a solid solution. In situ NAP-XPS, XANES, and HS-LEIS characterization indicated that Cu was initially present as Cu²⁺ cations dissolved in the Fe₂O₃ bulk lattice and reduced to metallic Cu⁰ nanoparticles (∼3 nm) on the external surface of the iron oxide support during the HT-WGS reactions. In situ HS-LEIS surface analysis also suggests that ∼1/3 of the surface of the Cu nanoparticles was covered by a FeO_x overlayer. The CO-TPR probe demonstrated that Cr does not chemically promote the iron oxide catalyst and that only Cu is a chemical promoter for the iron oxide HT-WGS catalysts. The Cu promoter introduces new catalytic active sites that enhance the reaction rates of the WGS reactions

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Section: Discussionmentioning

confidence: 76%

Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper

Zhu,

Rocha,

Lunkenbein

et al. 2016

ACS Catal.

106

118

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“…The chromium oxide is mainly added to suppress particle growth during the calcination treatment. 163,164 For similar reasons, sometimes silica is added. 165 Two mechanisms have been proposed in the literature.…”

Section: Active Phasesmentioning

confidence: 99%

The renaissance of iron-based Fischer–Tropsch synthesis: on the multifaceted catalyst deactivation behaviour

2008

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Iron-based Fischer-Tropsch catalysts, which are applied in the conversion of CO and H2 into longer hydrocarbon chains, are historically amongst the most intensively studied systems in heterogeneous catalysis. Despite this, fundamental understanding of the complex and dynamic chemistry of the iron-carbon-oxygen system and its implications for the rapid deactivation of the iron-based catalysts is still a developing field. Fischer-Tropsch catalysis is characterized by its multidisciplinary nature and therefore deals with a wide variety of fundamental chemical and physical problems. This critical review will summarize the current state of knowledge of the underlying mechanisms for the activation and eventual deactivation of iron-based Fischer-Tropsch catalysts and suggest systematic approaches for relating chemical identity to performance in next generation iron-based catalyst systems (210 references).

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“…An unsupported iron–chromium oxide catalyst was used to remove CO from the H 2 stream for the Haber–Bosch ammonia synthesis process because CO is a poison for the ammonia synthesis Fe-based catalyst . The iron–chromium oxide WGS catalyst technology was subsequently applied to control the H 2 /CO ratio of syngas for production of hydrogen from methane steam reforming, methanol synthesis, and Fischer–Tropsch synthesis of hydrocarbons. ,, Until the 1980s, the patent and scientific literature focused on improving the synthesis of the existing iron–chromium oxide catalyst. − Research in the 1980s began to explore, by trial-and-error, the effect of a wide range of promoters to try to stabilize surface area, increase activity, and enhance thermal stability of catalysts under the WGS reaction conditions. The additives can be broadly divided into two categories: chemical promoters (Cu, Rh) − and textural promoters (Cr, Al, Th, Zr, Zn, Mg). − …”

Section: Introductionmentioning

confidence: 99%

Iron-Based Catalysts for the High-Temperature Water–Gas Shift (HT-WGS) Reaction: A Review

2015

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This article critically reviews the literature on iron-based catalysts for the high-temperature water–gas shift (HT-WGS) reaction. The reaction mechanism, reaction intermediates, rate-determining step, kinetics, active site, and promoters are covered. Unlike the low-temperature water–gas shift (LT-WGS) reaction by Cu/ZnO catalysts that has received intensive analysis with modern in situ and operando spectroscopy and DFT studies, the corresponding HT-WGS reaction by Fe-based catalysts still lacks a fundamental understanding because of the absence of modern catalysis studies of this important catalytic system. Given the role of the WGS catalysts on production of H2 for a hydrogen economy, it is imperative that the fundamental molecular-level understanding of the HT-WGS catalyst be advanced.

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The role of Cr₂O₃ in Catalyst for Water‐Gas Shift Reaction

Abstract: The influence of Cr2O3 presence in the iron‐chromium catalysts for high‐temperature water‐gas shift reaction was studied. The surface stabilizing effect of Cr2O3 addition to Fe2O3, formed from iso‐ortho‐Fe(OH)3, was found. The two‐stage stabilizing effect was proved.

Cited by 13 publications

References 8 publications

Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper

Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper

The renaissance of iron-based Fischer–Tropsch synthesis: on the multifaceted catalyst deactivation behaviour

Iron-Based Catalysts for the High-Temperature Water–Gas Shift (HT-WGS) Reaction: A Review

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The role of Cr2O3 in Catalyst for Water‐Gas Shift Reaction

Abstract: The influence of Cr2O3 presence in the iron‐chromium catalysts for high‐temperature water‐gas shift reaction was studied. The surface stabilizing effect of Cr2O3 addition to Fe2O3, formed from iso‐ortho‐Fe(OH)3, was found. The two‐stage stabilizing effect was proved.

Cited by 13 publications

References 8 publications

Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper

Promotion Mechanisms of Iron Oxide-Based High Temperature Water–Gas Shift Catalysts by Chromium and Copper

The renaissance of iron-based Fischer–Tropsch synthesis: on the multifaceted catalyst deactivation behaviour

Iron-Based Catalysts for the High-Temperature Water–Gas Shift (HT-WGS) Reaction: A Review

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The role of Cr₂O₃ in Catalyst for Water‐Gas Shift Reaction