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The interaction of cobalt species with alumina on Co/Al2O3 catalysts prepared by atomic layer deposition

Paper ID Volume ID Publish Year Pages File Format Full-Text
42968 45949 2009 9 PDF Available
Title
The interaction of cobalt species with alumina on Co/Al2O3 catalysts prepared by atomic layer deposition
Abstract

Alumina supported cobalt catalysts were prepared by atomic layer deposition (ALD) of cobalt acetylacetonate precursors (Co(acac)2 and Co(acac)3). The main modes of interaction between the acetylacetonate precursors and the support were found to be the exchange reaction between the alumina OH-groups and the acac-ligands of the precursor and dissociative adsorption on coordinatively unsaturated Al3+ sites. The amount of precursor that could adsorb on the support was determined by steric hindrance. Samples were prepared using 1–5 reaction cycles, i.e. subsequent precursor addition (Co(acac)2) and calcination, resulting in catalysts containing ca. 3–10 wt.% Co. Samples were also prepared where the last calcination step was omitted, i.e. uncalcined catalysts. Calcination at 450 °C decreased the reducibility of the Co(acac)2/Al2O3 catalysts due to formation of a cobalt oxide phase strongly interacting with the support and aluminate type surface species. The reducibility increased with metal loading on both calcined and uncalcined catalysts; however the reducibility of the calcined catalysts remained lower than of the uncalcined ones. The dispersion was found to be lower on the calcined catalysts. The cobalt particle sizes on the calcined samples was ca. 8 nm and on the uncalcined 4–5 nm, for cobalt loadings of ca. 6–10 wt.%. Catalytic activity was tested by gas phase hydrogenation of toluene in temperature programmed mode (30–150 °C).

Graphical abstractAlumina supported cobalt catalysts were prepared by atomic layer deposition of cobalt acetylacetonate precursors. The interaction between cobalt species and the alumina support was studied. Calcination decreased the reducibility of the Co/Al2O3 catalysts due to formation of a cobalt oxide phase strongly interacting with the support and probably aluminate type surface species. The dispersion was also found to decrease due to calcination. The catalytic activity for toluene hydrogenation correlated with the cobalt surface area.Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Cobalt catalysts (supported); Alumina; Atomic layer deposition; ALD; Reducibility; Dispersion; Calcination; Toluene hydrogenation
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The interaction of cobalt species with alumina on Co/Al2O3 catalysts prepared by atomic layer deposition
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 360, Issue 2, 1 June 2009, Pages 183–191
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us