Temperature programmed desorption/reaction of ammonia over V[sub 2]O[sub 5]/TiO[sub 2] De-NO[sub x]ing catalysts

Journal Article · Sun May 01 00:00:00 EDT 1994 · Journal of Catalysis; (United States)

DOI:https://doi.org/10.1006/jcat.1994.1135· OSTI ID:7107388

Lietti, L; Forzatti, P ^[1]

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1. Dipartimento di Chimica Industriale ed Ingegneria Chimica, Milano (Italy)

Temperature programmed desorption (TPD) of ammonia, temperature programmed surface reaction (TPSR) of adsorbed ammonia with gas phase NO, temperature programmed reaction (TPR), and steady state reaction (SSR) experiments of NH[sub 3] + NO under diluted gas conditions in the presence and in the absence of oxygen are performed on a series of V[sub 2]O[sub 5]/TiO[sub 2] (anatase) catalysts with V[sub 2]O[sub 5] loadings [le]3.56% w/w that are comparable to those of commercial De-NO[sub x]ing catalysts. Both isolated vanadyls and polymeric metavanadate species are observed on the surface of submonolayer vanadia/titania samples, the relative concentration of the latter species increasing with the vanadia content. TPR, TPSR, and SSR experiments performed in the presence and in the absence of oxygen provide new and more direct evidence than previously reported in the literature for a greater reactivity of polymeric metavanadate species as compared to isolated vanadyls and for a faster reduction by NH[sub 3] and a faster reoxidation by gaseous oxygen of the polymeric metavanadate groups. This has been related to the presence of more labile oxygen atoms, that is beneficial for the activity but is also detrimental for the selectivity of the SCR reaction. The turnover frequency measured at 500 K under steady state conditions over high-vanadia loading catalysts is six times larger than that of low-vanadia loading catalysts, due to the higher amounts of polyvanadate species. The temperature window of the SCR reaction, corresponding to high NO conversion and complete selectivity to nitrogen, is shifted towards lower temperatures on increasing the vanadia loading and extends toward higher temperatures under steady state conditions and in the presence of oxygen due to a proper oxidation level of the catalyst. 27 refs., 7 figs., 3 tabs.

• OSTI ID: 7107388
• Journal Information: Journal of Catalysis; (United States), Vol. 147:1; ISSN 0021-9517
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
33 ADVANCED PROPULSION SYSTEMS
AMMONIA
CHEMICAL REACTIONS
NITRIC OXIDE
TITANIUM OXIDES
CATALYTIC EFFECTS
VANADIUM OXIDES
CATALYST SUPPORTS
CATALYSTS
HETEROGENEOUS CATALYSIS
SORPTIVE PROPERTIES
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0273-0400 K
TEMPERATURE RANGE 0400-1000 K
CATALYSIS
CHALCOGENIDES
HYDRIDES
HYDROGEN COMPOUNDS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NITROGEN OXIDES
OXIDES
OXYGEN COMPOUNDS
SURFACE PROPERTIES
TEMPERATURE RANGE
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VANADIUM COMPOUNDS
400201* - Chemical & Physicochemical Properties
330701 - Emission Control- Nitrogen Oxides