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On the synergy effect in MoO3-Fe2(MoO4)3 catalysts for methanol oxidation to formaldehyde

Söderhjelm, Emma; House, M. P.; Cruise, Neil; Holmberg, Johan; Bowker, M.; Bovin, Jan-Olov LU and Andersson, Arne LU (2008) In Topics in Catalysis 50(1-4). p.145-155
Abstract
Methanol oxidation to formaldehyde was studied over a series of Fe-Mo-O catalysts with various Mo/Fe atomic ratio and the end compositions Fe2O3 and MoO3. The activity data shows that the specific activity passes through a maximum with increase of the Mo content and is the highest for Fe2(MoO4)3. The selectivity to formaldehyde, on the other hand, increases with the Mo content in the catalyst. A synergy effect is observed in that a catalyst with the Mo/Fe ratio 2.2 is almost as active as Fe2(MoO4)3 and as selective as MoO3. Imaging of a MoO3/Fe2(MoO4)3 catalyst by SEM and TEM shows that the two phases form separate crystals, and HRTEM reveals the presence of an amorphous overlayer on the Fe2(MoO4)3 crystals. EDS line-scan analysis in STEM... (More)
Methanol oxidation to formaldehyde was studied over a series of Fe-Mo-O catalysts with various Mo/Fe atomic ratio and the end compositions Fe2O3 and MoO3. The activity data shows that the specific activity passes through a maximum with increase of the Mo content and is the highest for Fe2(MoO4)3. The selectivity to formaldehyde, on the other hand, increases with the Mo content in the catalyst. A synergy effect is observed in that a catalyst with the Mo/Fe ratio 2.2 is almost as active as Fe2(MoO4)3 and as selective as MoO3. Imaging of a MoO3/Fe2(MoO4)3 catalyst by SEM and TEM shows that the two phases form separate crystals, and HRTEM reveals the presence of an amorphous overlayer on the Fe2(MoO4)3 crystals. EDS line-scan analysis in STEM mode demonstrates that the Mo/Fe ratio in the amorphous layer is ~2.1 in the fresh catalyst and ~1.7 in the aged catalyst. The enrichment of Mo at the catalyst surface is confirmed by XPS data. Raman spectra give evidence for the Mo in the amorphous material being in octahedral coordination, which is in contrast to the crystalline Fe2(MoO4)3 bulk structure where Mo has tetrahedral coordination. XRD analysis gives no support for the formation of a defective molydate bulk structure. The results presented give strong support for the Mo rich amorphous structure being observed on the Fe2(MoO4)3 crystal surfaces being the active phase for methanol oxidation to formaldehyde. (Less)
Please use this url to cite or link to this publication:
author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
formaldehyde, methanol oxidation, Fe-Mo-O catalysts, electron microscopy, iron molybdate, XRD, TEM, HRTEM, SEM, XPS, Raman spectroscopy, STEM-EDS
in
Topics in Catalysis
volume
50
issue
1-4
pages
145 - 155
publisher
Kluwer
external identifiers
  • wos:000260319700016
  • scopus:55149099249
ISSN
1572-9028
DOI
10.1007/s11244-008-9112-1
language
English
LU publication?
yes
id
94eed190-8a14-439d-84c1-95ce4f0c76be (old id 1274326)
date added to LUP
2008-12-17 11:11:47
date last changed
2017-11-05 04:09:59
@article{94eed190-8a14-439d-84c1-95ce4f0c76be,
  abstract     = {Methanol oxidation to formaldehyde was studied over a series of Fe-Mo-O catalysts with various Mo/Fe atomic ratio and the end compositions Fe2O3 and MoO3. The activity data shows that the specific activity passes through a maximum with increase of the Mo content and is the highest for Fe2(MoO4)3. The selectivity to formaldehyde, on the other hand, increases with the Mo content in the catalyst. A synergy effect is observed in that a catalyst with the Mo/Fe ratio 2.2 is almost as active as Fe2(MoO4)3 and as selective as MoO3. Imaging of a MoO3/Fe2(MoO4)3 catalyst by SEM and TEM shows that the two phases form separate crystals, and HRTEM reveals the presence of an amorphous overlayer on the Fe2(MoO4)3 crystals. EDS line-scan analysis in STEM mode demonstrates that the Mo/Fe ratio in the amorphous layer is ~2.1 in the fresh catalyst and ~1.7 in the aged catalyst. The enrichment of Mo at the catalyst surface is confirmed by XPS data. Raman spectra give evidence for the Mo in the amorphous material being in octahedral coordination, which is in contrast to the crystalline Fe2(MoO4)3 bulk structure where Mo has tetrahedral coordination. XRD analysis gives no support for the formation of a defective molydate bulk structure. The results presented give strong support for the Mo rich amorphous structure being observed on the Fe2(MoO4)3 crystal surfaces being the active phase for methanol oxidation to formaldehyde.},
  author       = {Söderhjelm, Emma and House, M. P. and Cruise, Neil and Holmberg, Johan and Bowker, M. and Bovin, Jan-Olov and Andersson, Arne},
  issn         = {1572-9028},
  keyword      = {formaldehyde,methanol oxidation,Fe-Mo-O catalysts,electron microscopy,iron molybdate,XRD,TEM,HRTEM,SEM,XPS,Raman spectroscopy,STEM-EDS},
  language     = {eng},
  number       = {1-4},
  pages        = {145--155},
  publisher    = {Kluwer},
  series       = {Topics in Catalysis},
  title        = {On the synergy effect in MoO3-Fe2(MoO4)3 catalysts for methanol oxidation to formaldehyde},
  url          = {http://dx.doi.org/10.1007/s11244-008-9112-1},
  volume       = {50},
  year         = {2008},
}