The surface chemistry of vanadium oxide catalysts

Technical Report · Thu Sep 01 04:00:00 EDT 1988

OSTI ID:6758379

Lewis, Jr, K B

The surface chemistry of vanadium oxide catalysts was studied using uhv surface techniques and catalytic experiments at atmospheric pressure. In uhv, vanadium oxide films were grown on single crystal vanadium, Au(111), and Au foil substrates. Silica supported V/sub 2/O/sub 5/ was used in the catalytic experiments. Auger electron spectroscopy and low energy electron spectroscopy revealed temperature dependent surface segregation of contaminants on the V(110) surface. Temperature programmed desorption revealed both a surface and a bulk desorption state for hydrogen, and two desorption states for potassium on V(110). Recrystallized foils containing large grains with a V(100) orientation were also examined. Vanadium oxides films grown on a Au(111) substrate were ordered and exhibited a (..sqrt..3 /times/ ..sqrt..3) R30 /degree/ LEED pattern. The growth mode and preparation of these films is discussed. The structure and Auger spectrum of the films were consistent with a V/sub 2/O/sub 3/ surface. The TPD of hydrogen, ethanol, and ethylene were examined on this surface. Polycrystalline V/sub 2/O/sub 5/ supported on Au foil was also studied An oxidized surface was maintained through the facile surface segregation of lattice above 750 K. Two water desorption peaks were observed after the adsorption of predissociated hydrogen. CO, CO/sub 2/, and C/sub 2/H/sub 4/ were the principle desorption products after ethanol adsorption in uhv and at atmospheric pressure. The partial oxidation of methane and ethanol over V/sub 2/O/sub 5/ /minus/ SiO/sub 2/ was investigated. Methane oxidation with N/sub 2/O proceeded very slowly, however activation energies and rate laws were determined. Ethanol oxidation with O/sub 2/ was more rapid. Catalyst dispersions were measured using irreversible oxygen uptake following reduction at 641 K. Ethanol partial oxidation was structure insensitive. 137 refs., 58 figs., 3 tabs.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6758379
• Report Number(s): LBL-25846; ON: DE89007071
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102 -- Metals & Alloys-- Structure & Phase Studies
360202* -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
656002 -- Condensed Matter Physics-- General Techniques in Condensed Matter-- (1987-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AUGER ELECTRON SPECTROSCOPY
CATALYSTS
CHALCOGENIDES
CRYSTAL GROWTH
CRYSTAL STRUCTURE
ELECTRON SPECTROSCOPY
ELEMENTS
FILMS
GOLD
METALS
OXIDES
OXYGEN COMPOUNDS
RAMAN SPECTRA
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE DEPENDENCE
THIN FILMS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VANADIUM
VANADIUM COMPOUNDS
VANADIUM OXIDES