Vanadia supported on TiO sub 2 -SiO sub 2 mixed oxide gels: Structure of the dispersed phase and activity for the selective catalytic reduction of NO with NH sub 3
- Swiss Federal Inst. of Tech., Zurich (Switzerland)
- Univ. of Bayreuth (Germany)
Supported vanadia catalysts were prepared by reacting vanadyl triisopropoxide with titania-silica mixed oxide supports of fixed Ti:Si mol ratio (1:4 and 1:1), but of varying pore structure, surface area, and crystallinity. The latter properties were controlled by varying the sol-gel preparation parameters. Although the selectivity pattern for the selective catalytic reduction (SCR) remained essentially the same over all catalysts, the specific activity, defined on a per V{sup 5+} basis, varied with the support. The vanadia content in all catalysts corresponded to less than one monolayer (defined as 0.10 wt% V{sub 2}O{sub 5}m{sup 2} or 11 {mu}mol V{sup 5+}/m{sup 2}), and structural data indicate that the vanadia is will dispersed. Raman spectroscopy was used to differentiate between vanadia species immobilized on TiO{sub 2} and SiO{sub 2} domains, respectively. These results revealed that the mixed oxide gels can be categorized into two main types exhibiting titania- or silica-like behavior. A weak interaction that results from a two-stage hydrolysis procedure of the alkoxide precursors of the constituents is characteristic for silica-like supports. This contrasts with the titania-like behavior observed for TiO{sub 2}-SiO{sub 2} mixed oxides prepared by single-stage hydrolysis, where the vanadia-support interaction is strong. No crystalline V{sub 2}O{sub 5} phases were detected. TPR profiles show that the reducibility of vanadia, as evidenced by shifts in the temperature of maximum hydrogen consumption, is dependent upon the composition and preparation method of the mixed gel supports. An increase in the value of T{sub max} can be correlated with a decrease in the turnover frequency (NO converted per V{sup 5+} site) of the SCR reaction.
- OSTI ID:
- 7253016
- Journal Information:
- Journal of Catalysis; (United States), Vol. 133:1; ISSN 0021-9517
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effects of support composition and pretreatment conditions on the structure of vanadia dispersed on SiO{sub 2}, Al{sub 2}O{sub 3}, TiO{sub 2}, ZrO{sub 2}, and HfO{sub 2}
Vanadium oxide monolayer catalysts. III. A Raman spectroscopic and temperature-programmed reduction study of monolayer and crystal-type vanadia on various supports
Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
01 COAL, LIGNITE, AND PEAT
NITRIC OXIDE
SELECTIVE CATALYTIC REDUCTION
VANADIUM OXIDES
CATALYTIC EFFECTS
PHASE STUDIES
AMMONIA
CATALYST SUPPORTS
CATALYSTS
CHEMICAL PREPARATION
CRYSTAL STRUCTURE
DENITRIFICATION
FLUE GAS
GELS
MICROSTRUCTURE
POROSITY
QUANTITY RATIO
RAMAN SPECTROSCOPY
REDUCTION
SILICON OXIDES
SOLS
SURFACE AREA
TEMPERATURE CONTROL
TITANIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
COLLOIDS
CONTROL
DISPERSIONS
GASEOUS WASTES
HYDRIDES
HYDROGEN COMPOUNDS
LASER SPECTROSCOPY
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
SILICON COMPOUNDS
SPECTROSCOPY
SURFACE PROPERTIES
SYNTHESIS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
WASTES
400201* - Chemical & Physicochemical Properties
010800 - Coal
Lignite
& Peat- Waste Management