Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol

Abhijeet Gaur, Max Schumann, Kristian Viegaard Raun, Matthias Stehle, Pablo Beato, Anker Degn Jensen, Jan‐Dierk Grunwaldt, Martin Høj*

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

The structural changes of an iron molybdate/molybdenum oxide (Mo/Fe=2.0) catalyst for the selective oxidation of methanol to formaldehyde were studied using combined operando X‐ray absorption spectroscopy (XAS) and X‐ray diffraction (XRD) as well as operando Raman spectroscopy. Under operating conditions, the Mo K‐edge XANES spectra showed a transition from a mixture of α‐MoO3 and Fe2(MoO4)3 towards only Fe2(MoO4)3. XRD and Raman spectroscopy also showed disappearance of the α‐MoO3 phase with time on stream. The results evidenced that the α‐MoO3 component evaporated completely, while the Fe2(MoO4)3 component remained stable. This was linked to a decrease in catalytic activity. Further studies unraveled that the rate of α‐MoO3 evaporation increased with increasing MeOH concentration, decreasing O2 concentration and increasing temperature. The simultaneous measurements of catalytic activity and spectroscopy allowed to derive a structure‐activity relationship showing that α‐MoO3 evaporation needs to be prevented to optimize MoO3‐based catalysts for selective oxidation of methanol.
Original languageEnglish
JournalChemCatChem
Volume11
Issue number19
Pages (from-to)4871-4883
Number of pages13
ISSN1867-3880
DOIs
Publication statusPublished - 2019

Keywords

  • Formaldehyde
  • Operando XAS/XRD
  • Normalized difference edge analysis
  • Raman spectroscopy
  • Selective oxidation

Cite this

@article{98706e46b6404da5b60f735b08cc5607,
title = "Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol",
abstract = "The structural changes of an iron molybdate/molybdenum oxide (Mo/Fe=2.0) catalyst for the selective oxidation of methanol to formaldehyde were studied using combined operando X‐ray absorption spectroscopy (XAS) and X‐ray diffraction (XRD) as well as operando Raman spectroscopy. Under operating conditions, the Mo K‐edge XANES spectra showed a transition from a mixture of α‐MoO3 and Fe2(MoO4)3 towards only Fe2(MoO4)3. XRD and Raman spectroscopy also showed disappearance of the α‐MoO3 phase with time on stream. The results evidenced that the α‐MoO3 component evaporated completely, while the Fe2(MoO4)3 component remained stable. This was linked to a decrease in catalytic activity. Further studies unraveled that the rate of α‐MoO3 evaporation increased with increasing MeOH concentration, decreasing O2 concentration and increasing temperature. The simultaneous measurements of catalytic activity and spectroscopy allowed to derive a structure‐activity relationship showing that α‐MoO3 evaporation needs to be prevented to optimize MoO3‐based catalysts for selective oxidation of methanol.",
keywords = "Formaldehyde, Operando XAS/XRD, Normalized difference edge analysis, Raman spectroscopy, Selective oxidation",
author = "Abhijeet Gaur and Max Schumann and Raun, {Kristian Viegaard} and Matthias Stehle and Pablo Beato and Jensen, {Anker Degn} and Jan‐Dierk Grunwaldt and Martin H{\o}j",
year = "2019",
doi = "10.1002/cctc.201901025",
language = "English",
volume = "11",
pages = "4871--4883",
journal = "ChemCatChem",
issn = "1867-3880",
publisher = "Wiley - V C H Verlag GmbH & Co. KGaA",
number = "19",

}

Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol. / Gaur, Abhijeet; Schumann, Max; Raun, Kristian Viegaard; Stehle, Matthias; Beato, Pablo; Jensen, Anker Degn; Grunwaldt, Jan‐Dierk; Høj, Martin.

In: ChemCatChem, Vol. 11, No. 19, 2019, p. 4871-4883 .

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Operando XAS/XRD and Raman Spectroscopic Study of Structural Changes of the Iron Molybdate Catalyst during Selective Oxidation of Methanol

AU - Gaur, Abhijeet

AU - Schumann, Max

AU - Raun, Kristian Viegaard

AU - Stehle, Matthias

AU - Beato, Pablo

AU - Jensen, Anker Degn

AU - Grunwaldt, Jan‐Dierk

AU - Høj, Martin

PY - 2019

Y1 - 2019

N2 - The structural changes of an iron molybdate/molybdenum oxide (Mo/Fe=2.0) catalyst for the selective oxidation of methanol to formaldehyde were studied using combined operando X‐ray absorption spectroscopy (XAS) and X‐ray diffraction (XRD) as well as operando Raman spectroscopy. Under operating conditions, the Mo K‐edge XANES spectra showed a transition from a mixture of α‐MoO3 and Fe2(MoO4)3 towards only Fe2(MoO4)3. XRD and Raman spectroscopy also showed disappearance of the α‐MoO3 phase with time on stream. The results evidenced that the α‐MoO3 component evaporated completely, while the Fe2(MoO4)3 component remained stable. This was linked to a decrease in catalytic activity. Further studies unraveled that the rate of α‐MoO3 evaporation increased with increasing MeOH concentration, decreasing O2 concentration and increasing temperature. The simultaneous measurements of catalytic activity and spectroscopy allowed to derive a structure‐activity relationship showing that α‐MoO3 evaporation needs to be prevented to optimize MoO3‐based catalysts for selective oxidation of methanol.

AB - The structural changes of an iron molybdate/molybdenum oxide (Mo/Fe=2.0) catalyst for the selective oxidation of methanol to formaldehyde were studied using combined operando X‐ray absorption spectroscopy (XAS) and X‐ray diffraction (XRD) as well as operando Raman spectroscopy. Under operating conditions, the Mo K‐edge XANES spectra showed a transition from a mixture of α‐MoO3 and Fe2(MoO4)3 towards only Fe2(MoO4)3. XRD and Raman spectroscopy also showed disappearance of the α‐MoO3 phase with time on stream. The results evidenced that the α‐MoO3 component evaporated completely, while the Fe2(MoO4)3 component remained stable. This was linked to a decrease in catalytic activity. Further studies unraveled that the rate of α‐MoO3 evaporation increased with increasing MeOH concentration, decreasing O2 concentration and increasing temperature. The simultaneous measurements of catalytic activity and spectroscopy allowed to derive a structure‐activity relationship showing that α‐MoO3 evaporation needs to be prevented to optimize MoO3‐based catalysts for selective oxidation of methanol.

KW - Formaldehyde

KW - Operando XAS/XRD

KW - Normalized difference edge analysis

KW - Raman spectroscopy

KW - Selective oxidation

U2 - 10.1002/cctc.201901025

DO - 10.1002/cctc.201901025

M3 - Journal article

VL - 11

SP - 4871

EP - 4883

JO - ChemCatChem

JF - ChemCatChem

SN - 1867-3880

IS - 19

ER -