Lewis acidity as an explanation for oxide promotion of metals

implications of its importance and limits for catalytic reactions

A. B. Boffa, Chiu-Hsun Lin, A. T. Bell, G. A. Somorjai

Research output: Contribution to journalArticle

74 Citations (Scopus)

Abstract

Sub-monolayer quantities of metal oxides are found to influence CO hydrogenation, CO2 hydrogenation, acetone hydrogenation, ethylene hydroformylation, ethylene hydrogenation, and ethane hydrogenolysis over Rh foils. The metal oxides investigated include AlOx, TiOx, VOx, FeOx, ZrOx, NbOx, TaOx, and WOx. Only those reactions involving the hydrogenation of C-O bonds are enhanced by the oxide overlayers. The coverage at which maximum rate enhancement occurs is approximately 0.5 ML for each oxide promoter. Titanium, niobium, and tantalum oxides are the most effective promoters. XPS measurements after reaction show that of the oxides studied titanium, niobium, and tantalum oxide overlayers are stable in the highest oxidation states. The trend in promotion effectiveness is attributed to the direct relationship between oxidation state and Lewis acidity. For the oxide promoters, bonding at the metal oxide/metal interface between the O-end of adsorbed CO and the Lewis acidic oxide is postulated to facilitate C-O bond dissociation and subsequent hydrogenation.

Original languageEnglish
Pages (from-to)243-249
Number of pages7
JournalCatalysis Letters
Volume27
Issue number3-4
DOIs
Publication statusPublished - 1994 Sep 1

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Acidity
Oxides
Hydrogenation
Metals
Niobium oxide
Tantalum oxides
Titanium oxides
Carbon Monoxide
Ethylene
Hydroformylation
Oxidation
Hydrogenolysis
Ethane
Acetone
Metal foil
Monolayers
X ray photoelectron spectroscopy

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)

Cite this

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title = "Lewis acidity as an explanation for oxide promotion of metals: implications of its importance and limits for catalytic reactions",
abstract = "Sub-monolayer quantities of metal oxides are found to influence CO hydrogenation, CO2 hydrogenation, acetone hydrogenation, ethylene hydroformylation, ethylene hydrogenation, and ethane hydrogenolysis over Rh foils. The metal oxides investigated include AlOx, TiOx, VOx, FeOx, ZrOx, NbOx, TaOx, and WOx. Only those reactions involving the hydrogenation of C-O bonds are enhanced by the oxide overlayers. The coverage at which maximum rate enhancement occurs is approximately 0.5 ML for each oxide promoter. Titanium, niobium, and tantalum oxides are the most effective promoters. XPS measurements after reaction show that of the oxides studied titanium, niobium, and tantalum oxide overlayers are stable in the highest oxidation states. The trend in promotion effectiveness is attributed to the direct relationship between oxidation state and Lewis acidity. For the oxide promoters, bonding at the metal oxide/metal interface between the O-end of adsorbed CO and the Lewis acidic oxide is postulated to facilitate C-O bond dissociation and subsequent hydrogenation.",
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Lewis acidity as an explanation for oxide promotion of metals : implications of its importance and limits for catalytic reactions. / Boffa, A. B.; Lin, Chiu-Hsun; Bell, A. T.; Somorjai, G. A.

In: Catalysis Letters, Vol. 27, No. 3-4, 01.09.1994, p. 243-249.

Research output: Contribution to journalArticle

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T1 - Lewis acidity as an explanation for oxide promotion of metals

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AU - Boffa, A. B.

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AU - Bell, A. T.

AU - Somorjai, G. A.

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