Vanadia, vanadia-titania, and vanadia-titania-silica gels: Structural genesis and catalytic behavior in the reduction of nitric oxide with ammonia

Journal Article · Sun Mar 01 04:00:00 EST 1992 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1016/0021-9517(92)90211-Y· OSTI ID:7161912

Handy, B E; Maciejewski, M; Baiker, A ^[1]

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1. 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), Journal Name: Journal of Catalysis; (United States) Vol. 134:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ADSORBENTS
AMMONIA
AMORPHOUS STATE
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COHERENT SCATTERING
COLLOIDS
CRYSTALLIZATION
DECOMPOSITION
DENITRIFICATION
DIFFERENTIAL THERMAL ANALYSIS
DIFFRACTION
DISPERSIONS
ELECTRON MICROSCOPY
GELS
GRAVIMETRIC ANALYSIS
HEAT TREATMENTS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROLYSIS
LYSIS
MASS SPECTROSCOPY
MICROSCOPY
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHASE TRANSFORMATIONS
QUANTITATIVE CHEMICAL ANALYSIS
REDUCTION
SCATTERING
SELECTIVE CATALYTIC REDUCTION
SILICA GEL
SOLVOLYSIS
SPECTROSCOPY
SURFACE AREA
SURFACE PROPERTIES
SYNTHESIS
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
VANADIUM OXIDES
X-RAY DIFFRACTION