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Oxidation of methanol to formaldehyde on cation vacant Fe-V-Mo-oxide

Massa, Mariano LU ; Häggblad, Robert LU ; Hansen, Staffan LU and Andersson, Arne LU (2011) In Applied Catalysis A: General 408(1-2). p.63-72
Abstract
A spinel-type catalyst of the composition Fe(2.50(1-z/3))V(0.20(1-z/3))Mo(0.30(1-z/3))square(z)O(4), where z is the number of cation vacancies (El), was prepared under reducing atmosphere. From the reduced sample a number of preoxidized samples were made by TPO treatment of the reduced material to different end temperatures ranging from 150 to 450 degrees C. XRD shows that the spinel-type structure is maintained irrespective of the degree of preoxidation of the sample and the related increasing number of cation vacancies. The number of cation vacancies z increases from 0.12 for the most reduced sample up to 0.62 for the most oxidized sample. XANES data reveals that in the most reduced sample the cations are essentially Fe(2+),Fe(3+),... (More)
A spinel-type catalyst of the composition Fe(2.50(1-z/3))V(0.20(1-z/3))Mo(0.30(1-z/3))square(z)O(4), where z is the number of cation vacancies (El), was prepared under reducing atmosphere. From the reduced sample a number of preoxidized samples were made by TPO treatment of the reduced material to different end temperatures ranging from 150 to 450 degrees C. XRD shows that the spinel-type structure is maintained irrespective of the degree of preoxidation of the sample and the related increasing number of cation vacancies. The number of cation vacancies z increases from 0.12 for the most reduced sample up to 0.62 for the most oxidized sample. XANES data reveals that in the most reduced sample the cations are essentially Fe(2+),Fe(3+), V(3+), Mo(4+) and Mo(5+) in the bulk, whereas the most oxidized sample has Fe(3+), V(4+) and Mo(6+). XPS analysis shows that at the surface the metals are mainly in their highest oxidation state, i.e. Fe(3+),V(5+) and Me(6+). Irrespective of the degree of preoxidation of the catalyst, the same catalytic performance and composition of both the surface and the bulk are approached when the samples are used in methanol oxidation. Both the activity and the selectivity to formaldehyde increase initially with time-on-stream, and in parallel there is some enrichment of vanadium and molybdenum taking place at the surface. At steady state conditions the spinel-type catalyst gives a selectivity to formaldehyde of about 86% at high methanol conversion. Our results demonstrate that the spinel-type structure is flexible and stable at both reducing and oxidizing conditions, allowing the cations to change valence while maintaining the same basic structure type. Moreover, the spinel-type catalyst is stable towards volatilization. (C) 2011 Elsevier B.V. All rights reserved. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Fe-V-Mo-oxide, Spinel-type catalyst, Cation vacancies, XRD, XANES, XPS, Methanol oxidation, Formaldehyde
in
Applied Catalysis A: General
volume
408
issue
1-2
pages
63 - 72
publisher
Elsevier
external identifiers
  • wos:000297188200007
  • scopus:80054931062
ISSN
0926-860X
DOI
10.1016/j.apcata.2011.09.015
language
English
LU publication?
yes
id
47a52615-4e03-43e1-b812-844c38b67e9a (old id 2300028)
date added to LUP
2012-01-20 10:02:29
date last changed
2017-08-20 04:00:35
@article{47a52615-4e03-43e1-b812-844c38b67e9a,
  abstract     = {A spinel-type catalyst of the composition Fe(2.50(1-z/3))V(0.20(1-z/3))Mo(0.30(1-z/3))square(z)O(4), where z is the number of cation vacancies (El), was prepared under reducing atmosphere. From the reduced sample a number of preoxidized samples were made by TPO treatment of the reduced material to different end temperatures ranging from 150 to 450 degrees C. XRD shows that the spinel-type structure is maintained irrespective of the degree of preoxidation of the sample and the related increasing number of cation vacancies. The number of cation vacancies z increases from 0.12 for the most reduced sample up to 0.62 for the most oxidized sample. XANES data reveals that in the most reduced sample the cations are essentially Fe(2+),Fe(3+), V(3+), Mo(4+) and Mo(5+) in the bulk, whereas the most oxidized sample has Fe(3+), V(4+) and Mo(6+). XPS analysis shows that at the surface the metals are mainly in their highest oxidation state, i.e. Fe(3+),V(5+) and Me(6+). Irrespective of the degree of preoxidation of the catalyst, the same catalytic performance and composition of both the surface and the bulk are approached when the samples are used in methanol oxidation. Both the activity and the selectivity to formaldehyde increase initially with time-on-stream, and in parallel there is some enrichment of vanadium and molybdenum taking place at the surface. At steady state conditions the spinel-type catalyst gives a selectivity to formaldehyde of about 86% at high methanol conversion. Our results demonstrate that the spinel-type structure is flexible and stable at both reducing and oxidizing conditions, allowing the cations to change valence while maintaining the same basic structure type. Moreover, the spinel-type catalyst is stable towards volatilization. (C) 2011 Elsevier B.V. All rights reserved.},
  author       = {Massa, Mariano and Häggblad, Robert and Hansen, Staffan and Andersson, Arne},
  issn         = {0926-860X},
  keyword      = {Fe-V-Mo-oxide,Spinel-type catalyst,Cation vacancies,XRD,XANES,XPS,Methanol oxidation,Formaldehyde},
  language     = {eng},
  number       = {1-2},
  pages        = {63--72},
  publisher    = {Elsevier},
  series       = {Applied Catalysis A: General},
  title        = {Oxidation of methanol to formaldehyde on cation vacant Fe-V-Mo-oxide},
  url          = {http://dx.doi.org/10.1016/j.apcata.2011.09.015},
  volume       = {408},
  year         = {2011},
}