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Water Inhibition in Methane Oxidation over Alumina Supported Palladium Catalysts

Velin, Peter ; Ek, Martin LU orcid ; Skoglundh, Magnus ; Schaefer, Andreas ; Raj, Agnes ; Thompsett, David ; Smedler, Gudmund and Carlsson, Per Anders (2019) In Journal of Physical Chemistry C 123(42). p.25724-25737
Abstract

In situ diffuse reflectance infrared Fourier transform spectroscopy has been used to distinguish surface hydroxyl groups on Al2O3 and PdO/Al2O3 model catalysts calcined at 500-900 °C. Employing the operando approach, the formation of surface hydroxyl groups has been correlated to the methane oxidation activity for PdO/Al2O3 catalysts using a PdO powder sample as reference. The results show that the alumina support stabilizes active PdO particles leading to enhanced apparent methane turnover frequency (TOF), which decreases slowly in dry conditions due to alumina hydroxylation. Wet conditions cause severe hydroxylation that is detrimental for the methane TOF. The... (More)

In situ diffuse reflectance infrared Fourier transform spectroscopy has been used to distinguish surface hydroxyl groups on Al2O3 and PdO/Al2O3 model catalysts calcined at 500-900 °C. Employing the operando approach, the formation of surface hydroxyl groups has been correlated to the methane oxidation activity for PdO/Al2O3 catalysts using a PdO powder sample as reference. The results show that the alumina support stabilizes active PdO particles leading to enhanced apparent methane turnover frequency (TOF), which decreases slowly in dry conditions due to alumina hydroxylation. Wet conditions cause severe hydroxylation that is detrimental for the methane TOF. The hydroxylation follows two different routes, i.e., spillover of hydrogen-containing species to the PdO-Al2O3 boundary and/or the close proximity of the supported PdO particles and under wet conditions also dissociation of gas phase water on the entire alumina surface. Both hydroxylation routes obey varying kinetics such that near saturation is reached quickly (minutes) followed by a continuous slow growth for prolonged exposure times (hours). At low temperatures, inhibition of palladium active sites on the rim of the PdO particles close to alumina seems to be of particular importance for the observed detrimental effect of water, whereas water induced morphological changes (no sintering observed) of the PdO particles play a minor role.

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author
; ; ; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
123
issue
42
pages
25724 - 25737
publisher
The American Chemical Society (ACS)
external identifiers
  • scopus:85073221729
ISSN
1932-7447
DOI
10.1021/acs.jpcc.9b07606
project
Understanding of Catalysts for Climate-Neutral Chemicals by in situ Transmission Electron Microscopy Characterization
language
English
LU publication?
yes
id
4363bc6b-167b-460a-95e1-4efbc09a16a2
date added to LUP
2019-10-25 12:05:23
date last changed
2022-04-18 18:19:35
@article{4363bc6b-167b-460a-95e1-4efbc09a16a2,
  abstract     = {{<p>In situ diffuse reflectance infrared Fourier transform spectroscopy has been used to distinguish surface hydroxyl groups on Al<sub>2</sub>O<sub>3</sub> and PdO/Al<sub>2</sub>O<sub>3</sub> model catalysts calcined at 500-900 °C. Employing the operando approach, the formation of surface hydroxyl groups has been correlated to the methane oxidation activity for PdO/Al<sub>2</sub>O<sub>3</sub> catalysts using a PdO powder sample as reference. The results show that the alumina support stabilizes active PdO particles leading to enhanced apparent methane turnover frequency (TOF), which decreases slowly in dry conditions due to alumina hydroxylation. Wet conditions cause severe hydroxylation that is detrimental for the methane TOF. The hydroxylation follows two different routes, i.e., spillover of hydrogen-containing species to the PdO-Al<sub>2</sub>O<sub>3</sub> boundary and/or the close proximity of the supported PdO particles and under wet conditions also dissociation of gas phase water on the entire alumina surface. Both hydroxylation routes obey varying kinetics such that near saturation is reached quickly (minutes) followed by a continuous slow growth for prolonged exposure times (hours). At low temperatures, inhibition of palladium active sites on the rim of the PdO particles close to alumina seems to be of particular importance for the observed detrimental effect of water, whereas water induced morphological changes (no sintering observed) of the PdO particles play a minor role.</p>}},
  author       = {{Velin, Peter and Ek, Martin and Skoglundh, Magnus and Schaefer, Andreas and Raj, Agnes and Thompsett, David and Smedler, Gudmund and Carlsson, Per Anders}},
  issn         = {{1932-7447}},
  language     = {{eng}},
  number       = {{42}},
  pages        = {{25724--25737}},
  publisher    = {{The American Chemical Society (ACS)}},
  series       = {{Journal of Physical Chemistry C}},
  title        = {{Water Inhibition in Methane Oxidation over Alumina Supported Palladium Catalysts}},
  url          = {{http://dx.doi.org/10.1021/acs.jpcc.9b07606}},
  doi          = {{10.1021/acs.jpcc.9b07606}},
  volume       = {{123}},
  year         = {{2019}},
}