The effects of structure on the catalytic activity and selectivity of V[sub 2]O[sub 5]/TiO[sub 2] for the reduction of NO by NH[sub 3]

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

DOI:https://doi.org/10.1016/0021-9517(92)90337-H· OSTI ID:6914585

Went, G T; Leu, Li-Jen; Rosin, R R; Bell, A T ^[1]

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1. Univ. of California, Berkeley (United States)

An investigation of the effect of catalyst structure on the activity and selectivity of TiO[sub 2] (anatase)-supported V[sub 2]O[sub 5] for the selective catalytic reduction of NO by NH[sub 3] has been carried out. The structure of the catalyst and the adsorbed species was characterized by in situ laser Raman spectroscopy (LRS). At vanadia loadings corresponding to less than a theoretical monolayer, the vanadia is present in the form of monomeric vanadyl and polymeric vanadate species. When the vanadia coverage exceeds a monolayer, crystallites of V[sub 2]O[sub 5] form at the expense of the polymeric species. The specific activity of the polymeric vanadates species is about 10 times greater than that of the monomeric vanadyl species. Monomeric species produce N[sub 2] as the principle reactions product, independent of the presence or absence of O[sub 2] in the feed, whereas polymeric vanadates species produce both N[sub 2] and N[sub 2]O, with the selectivity to N[sub 2] decreasing with increasing concentrations of O[sub 2] in the feed. LRS experiments reveal that in the absence of O[sub 2] in the feed stream, the catalyst undergoes reduction but that in the presence of O[sub 2], the catalyst remains in a nearly fully oxidized state. TPD experiments indicate that a crucial step in the catalytic reduction of NO is the activation of adsorbed NH[sub 3] to produce NH[sub x] (x = 0 [minus] 2) species. The removal of H atoms from adsorbed NH[sub 3] occurs via reaction with V [double bond] O groups present in clusters of monomeric vanadyl species and in polymeric vanadate species. The observations reported in this study and interpreted in terms of a reaction mechanism.

• OSTI ID: 6914585
• Journal Information: Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 134:2; ISSN 0021-9517; ISSN JCTLA5
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010800 -- Coal
Lignite
& Peat-- Waste Management
36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure & Phase Studies
54 ENVIRONMENTAL SCIENCES
540120* -- Environment
Atmospheric-- Chemicals Monitoring & Transport-- (1990-)
AMMONIA
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CONTROL
DENITRIFICATION
DESORPTION
ELEMENTS
HYDRIDES
HYDROGEN COMPOUNDS
KINETICS
LASER SPECTROSCOPY
MOLECULAR STRUCTURE
NITRIC OXIDE
NITROGEN
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
NITROUS OXIDE
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
RAMAN SPECTROSCOPY
REACTION INTERMEDIATES
REACTION KINETICS
REDUCTION
SELECTIVE CATALYTIC REDUCTION
SORPTION
SPECTROSCOPY
SYNTHESIS
TEMPERATURE CONTROL
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
VANADATES
VANADIUM COMPOUNDS
VANADIUM OXIDES