Vanadium oxide deposited on an Rh foil: CO and CO[sub 2] hydrogenation reactivity
- Lawrence Berkeley Lab., CA (United States) Univ. of California, Berkeley (United States)
The effects of submonolayer deposits of vanadia on the rates of CO and CO[sub 2] hydrogenation of an Rh foil have been examined. Auger electron spectroscopy (AES), ion scattering spectroscopy (ISS), and temperature-programmed desorption (TPD) have been used to determine the oxide coverage, and X-ray photoelectron spectroscopy (XPS) has been used to determine the oxidation state for VO[sub x] deposits on a rhodium foil. After oxidation (3 [times] 10[sup [minus]6] O[sub 2] at 350[degrees]C), the vanadium valence state is 3+, which corresponds to an oxide stoichiometry of V[sub 2]O[sub 3]. CO chemisorption reduces 34% of the V[sup 3+] to V[sup 2+] at low oxide coverages. The absolute amount of V[sup 2+] in the oxide overlayer after CO titration is found to maximize at a coverage of 0.5 ML. The rates of CO and CO[sub 2] hydrogenation increase upon addition of VO[sub x] to an Rh foil. For CO hydrogenation, the rate maximizes at two times that of the rate on the clean surface at an oxide coverage of 0.4 ML. For CO[sub 2] hydrogenation, the rate maximizes at six times that of the clean surface rate at an oxide coverage of 0.6 ML. The oxide promoter also alters the activation energies, partial pressure dependences, and selectivities for the hydrogenation reactions. A comparison of the kinetic and spectroscopic data reveals a strong correlation between the degree of reducibility of the oxide overlayer and the amount of rate enhancement for CO and CO[sub 2] hydrogenation. 29 refs., 9 figs., 2 tabs.
- OSTI ID:
- 6046061
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 139:2; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACTIVATION ENERGY
AUGER ELECTRON SPECTROSCOPY
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
CHEMISORPTION
DESORPTION
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY
HETEROGENEOUS CATALYSIS
HYDROGENATION
IONS
METALS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PARTIAL PRESSURE
PHOTOELECTRON SPECTROSCOPY
PLATINUM METALS
RHODIUM
SCATTERING
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
STOICHIOMETRY
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VALENCE
VANADIUM COMPOUNDS
VANADIUM OXIDES
X-RAY SPECTROSCOPY