Vanadium oxide monolayer catalysts. III. A Raman spectroscopic and temperature-programmed reduction study of monolayer and crystal-type vanadia on various supports

Journal Article · Thu Oct 16 04:00:00 EDT 1980 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100458a023· OSTI ID:6824048

Roozeboom, F; Mittelmeijer-Hazeleger, M C; Moulijn, J A; Medema, J; de Beer, V H.J.; Gellings, P J

Vanadium(V) oxide supported on ..gamma..-Al/sub 2/O/sub 3/,CeO/sub 2/,Cr/sub 2/O/sub 3/,SiO/sub 2/,TiO/sub 2/, and ZrO/sub 2/ was studied by x-ray fluorescence, by x-ray diffraction, and especially by the combination of Raman spectroscopy and temperature programmed reduction (TPR) for qualitative and quantitative structural analysis, respectively. Catalysts were prepared via ion-exchange and wet-impregnation methods. The V contents ranged from approx. 1 to 40 wt % V. At low surface concentrations only surface vanadate phases of two-dimensional character are observed for all carriers. According to Raman and TPR data the structure of these surface vanadate species is independent of the preparation technique. At medium and high surface concentrations, the wet-impregnated samples already contain crystalline V/sub 2/O/sub 5/. At equal surface concentrations the ion-exchanged catalysts contain no V/sub 2/O/sub 5/ crystallites. An exception is SiO/sub 2/ on which also crystalline V/sub 2/O/sub 5/ is formed in both preparation techniques. Monolayer stability toward thermal treatment decreases in the order Al/sub 2/O/sub 3/ > TiO/sub 2/ > CeO/sub 2/, whereas on heating ion-exchanged V/SiO/sub 2/ the crystalline V/sub 2/O/sub 5/ spreads out over the silica surface. The reducibilities of the ion-exchanged catalysts, as measured by TPR, can be used as a measure for the contact interaction between vanadia and the carrier oxides. At temperatures of 500 to 800 K, this interaction ranges from strong with titania to weak with silica as a carrier.

• Research Organization: Twente Univ. of Tech., Enschede, Netherlands
• OSTI ID: 6824048
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 84:21; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ADSORPTION
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CATALYST SUPPORTS
CATALYTIC EFFECTS
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
CHROMIUM COMPOUNDS
CHROMIUM OXIDES
COHERENT SCATTERING
COMPARATIVE EVALUATIONS
CRYSTALS
DIFFRACTION
HIGH TEMPERATURE
IMPREGNATION
ION EXCHANGE
NONDESTRUCTIVE ANALYSIS
OXIDES
OXYGEN COMPOUNDS
QUALITATIVE CHEMICAL ANALYSIS
QUANTITATIVE CHEMICAL ANALYSIS
RAMAN SPECTRA
RARE EARTH COMPOUNDS
REDUCTION
SCATTERING
SILICON COMPOUNDS
SILICON OXIDES
SORPTION
SPECTRA
STRUCTURAL CHEMICAL ANALYSIS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM OXIDES
X-RAY DIFFRACTION
X-RAY EMISSION ANALYSIS
X-RAY FLUORESCENCE ANALYSIS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES