Vanadium dispersion and catalytic activity of Pd/VOx/SBA-15 catalysts in the Wacker oxidation of ethylene

R. Barthos, András Hegyessy, Szilvia Klébert, J. Valyon

Research output: Contribution to journalArticle

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Abstract

Transmission electron microscopy (TEM), X-ray diffractometry (XRD), in situ diffuse reflectance ultra violet - visible (UV-Vis) spectroscopy, and temperature-programmed reduction by hydrogen (H2-TPR) were used to identify the vanadia forms in vanadium-containing SBA-15 preparations (VOx/SBA-15). Wacker type supported Pd/VOx/SBA-15 catalysts were obtained by introducing Pd into VOx/SBA-15 samples using conventional impregnation method. The activity of the catalysts was tested in the gas phase partial oxidation of ethylene by O2 in the presence of H2O (Wacker oxidation). VOx/SBA-15 sample was obtained by micelle-templated synthesis using vanadium-containing synthesis gel. The vanadium became incorporated in the silica structure from the gel in near to atomic dispersion. This catalyst was quite active in ethylene oxidation to CO2 but had low Wacker activity. Isolated, polymeric and bulk vanadia species were identified in the VOx/SBA-15 prepared by wet impregnation/calcination method. The specific surface area of the sample was found to be smaller than that of the neat SBA-15 support because some pores were blocked by vanadia agglomerates. The corresponding Pd/VOx/SBA-15 catalyst showed high selectivity for acetaldehyde formation but the activity was relatively low due to low accessible active surface. A third VOx/SBA-15 sample was obtained by applying directed surface reaction between silanol groups of dehydrated SBA-15 and anhydrous solution of vanadyl acetylacetonate. Large number of accessible Pd/VOx sites were present in the corresponding Pd/VOx/SBA-15 catalyst. Latter catalyst induced ethylene oxidation to acetaldehyde with high yield at temperatures ≤ 160°C and with good yield to acetic acid at temperatures ≥ 160°C.

Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalMicroporous and Mesoporous Materials
Volume207
DOIs
Publication statusPublished - May 1 2015

Fingerprint

Vanadium
vanadium
catalytic activity
Catalyst activity
Ethylene
ethylene
catalysts
Oxidation
oxidation
Catalysts
Acetaldehyde
acetaldehyde
Impregnation
Gels
gels
Catalyst selectivity
Ultraviolet visible spectroscopy
Surface reactions
synthesis
acetic acid

Keywords

  • H-tpr
  • Sba-15, pd/v catalysts
  • UV-Vis
  • Wacker oxidation

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Chemistry(all)
  • Condensed Matter Physics

Cite this

Vanadium dispersion and catalytic activity of Pd/VOx/SBA-15 catalysts in the Wacker oxidation of ethylene. / Barthos, R.; Hegyessy, András; Klébert, Szilvia; Valyon, J.

In: Microporous and Mesoporous Materials, Vol. 207, 01.05.2015, p. 1-8.

Research output: Contribution to journalArticle

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AU - Valyon, J.

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