Vanadia, vanadia-titania, and vanadia-titania-silica gels: Structural genesis and catalytic behavior in the reduction of nitric oxide with ammonia
- Swiss Federal Inst. of Tech., Zuerich (Switzerland)
Metal oxide xerogels were prepared by the hydrolysis of vanadium, titanium, and silicon alkoxides. The structural and chemical transformations of the gels occurring during thermal treatment under oxidizing and inert gas atmosphere were studied using thermoanalytical methods (TG, DTA) combined with mass spectroscopy, X-ray diffraction, and electron microscopy. Crystallization of the amorphous vanadia was found to be considerably retarded in the mixed gels compared to the pure vanadia gel. The mixed gels remain amorphous at 520 K, whereas crystallization already occurs in the pure vanadia gel at this temperature. All mixed gel phases separate after stabilization at 870 K, with the formation of V{sub 2}O{sub 5} platelets and globular TiO{sub 2} (anatase) particles. No other phases were detected by X-ray diffraction at this temperature. Addition of silica sol increases the overall surface area of the gel catalysts. This, however, does not increases the dispersion of vanadia in the amorphous matrix or stabilize it sufficiently to prevent crystallization under oxidizing conditions. Heat treatment of the gels at temperatures close to the melting point of vanadia results in rapid transformation of anatase to rutile. The stability and catalytic activity of the gels for the selective catalytic reduction of NO with NH{sub 3} (SCR) were studied following thermal treatments under in situ and oxidizing (7% O{sub 2}) atmosphere. Low temperature SCR testing (T {le} 520 K) showed that the same kinetic behavior typical of titania-supported vanadia exists in all gels, with activity behavior being a function of gel composition an dispersion.
- OSTI ID:
- 7161912
- Journal Information:
- Journal of Catalysis; (United States), Vol. 134:1; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
01 COAL, LIGNITE, AND PEAT
CATALYSTS
CHEMICAL PREPARATION
NITRIC OXIDE
SELECTIVE CATALYTIC REDUCTION
SILICA GEL
CATALYTIC EFFECTS
PHASE STUDIES
TITANIUM OXIDES
VANADIUM OXIDES
AMMONIA
AMORPHOUS STATE
CRYSTALLIZATION
DIFFERENTIAL THERMAL ANALYSIS
ELECTRON MICROSCOPY
GELS
HEAT TREATMENTS
HYDROLYSIS
MASS SPECTROSCOPY
OXIDATION
PHASE TRANSFORMATIONS
SURFACE AREA
THERMAL GRAVIMETRIC ANALYSIS
X-RAY DIFFRACTION
ADSORBENTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL REACTIONS
COHERENT SCATTERING
COLLOIDS
DECOMPOSITION
DENITRIFICATION
DIFFRACTION
DISPERSIONS
GRAVIMETRIC ANALYSIS
HYDRIDES
HYDROGEN COMPOUNDS
LYSIS
MICROSCOPY
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
QUANTITATIVE CHEMICAL ANALYSIS
REDUCTION
SCATTERING
SOLVOLYSIS
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
THERMAL ANALYSIS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
400201* - Chemical & Physicochemical Properties
540120 - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)
010800 - Coal
Lignite
& Peat- Waste Management