Characterization of the nature of surface sites on vanadia-titania catalysts by FTIR

Journal Article · Mon Apr 01 00:00:00 EST 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90307-P· OSTI ID:5679016

Topsoee, Nan-Yu ^[1]

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1. Haldor Topsoee Research Laboratories, Lyngby (Denmark)

With the aim of understanding the vanadia-titania catalysts used for selective catalytic reduction of NO by NH{sub 3} in the SCR DeNO{sub x} process, the surface structure of vanadia, titania, and vanadia supported on titania catalysts were studied by FTIR. The interactions of NO, NH{sub 3}, and No + NH{sub 3} with the catalysts in different states of oxidation/reduction have been investigated. Extensive reduction in H{sub 2} of the vanadia-titania sample broke up the surface vanadia structure, eliminated the V-OH species, and reexposed the surface Ti-OH groups. Adsorption of NH{sub 3} on the surface demonstrated the presence of both Broensted and Lewis acid sites on the vanadia-titania catalysts, while Broensted and Lewis acid sites were observed to dominate on V{sub 2}O{sub 5} and TiO{sub 5}, respectively. The ratio of Broensted to Lewis acid sites on the vanadia-titania catalysts was found to depend on the number of V-OH and V{double bond}O groups, the vanadia loading, or the vanadia coverage, as well as the oxidation state of vanadia. No adsorption of NO was evidenced on the oxidized or the NH{sub 3}-reduced surface of vanadia-titania and adsorption occurred only on the h{sub 2}-reduced samples. On a partially reduced catalyst with preadsorbed NH{sub 3}, NO was observed to oxidized the surface at room temperature accompanied by a transformation of Lewis to Broensted acid sites. The redox properties of these catalysts were found to play an essential role in the surface adsorption/reaction process. Evidence of interaction of NO with surface NH{sup +}{sub 4} species further suggested the importance of Broensted acid sites and thus also the V-OH groups in the SCR DeNO{sub x} reaction mechanism.

• OSTI ID: 5679016
• Journal Information: Journal of Catalysis; (USA), Vol. 128:2; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
01 COAL, LIGNITE, AND PEAT
20 FOSSIL-FUELED POWER PLANTS
NITRIC OXIDE
SELECTIVE CATALYTIC REDUCTION
TITANIUM OXIDES
CATALYTIC EFFECTS
SURFACE PROPERTIES
VANADIUM OXIDES
ADSORPTION
AIR POLLUTION CONTROL
AMMONIA
BROENSTED ACIDS
CATALYST SUPPORTS
CATALYSTS
FOURIER TRANSFORMATION
HYDROGEN
INFRARED RADIATION
LEWIS ACIDS
OXIDATION
REDUCTION
TITANIUM HYDROXIDES
VANADIUM HYDROXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CONTROL
DENITRIFICATION
ELECTROMAGNETIC RADIATION
ELEMENTS
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXIDES
INORGANIC ACIDS
INTEGRAL TRANSFORMATIONS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN COMPOUNDS
POLLUTION CONTROL
RADIATIONS
SORPTION
TITANIUM COMPOUNDS
TRANSFORMATIONS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
400201* - Chemical & Physicochemical Properties
540120 - Environment
Atmospheric- Chemicals Monitoring & Transport- (1990-)
010800 - Coal
Lignite
& Peat- Waste Management
200202 - Fossil-Fueled Power Plants- Waste Management- Noxious Gas & Particulate Emissions