Reactivity of V2O5Catalysts for the Selective Catalytic Reduction of NO by NH3: Influence of Vanadia Loading, H2O, and SO2

Amiridis, Michael D.; Wachs, Israel E.; Deo, Goutam; Jehng, Jih‐Mirn; Kim, Du Soung

doi:10.1006/jcat.1996.0182

Cited by 258 publications

(116 citation statements)

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“…Moreover, at high vanadia coverage V 2 O 5 blocks the active monolayer sites of toluene oxidation, decreasing the activity. This is in line with literature data for partial toluene [8] and o-xylene [31] oxidation as well as selective catalytic reduction of NO by NH 3 [32].…”

Section: Discussionsupporting

confidence: 92%

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

2004

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Pure and K-doped vanadia/titania prepared by different methods have been studied in order to elucidate the role of vanadia species (monomeric, polymeric, bulk) in catalytic toluene partial oxidation. The ratio of different vanadia species was controlled by treating the catalysts in diluted HNO 3 , which removes bulk vanadia and polymeric vanadia species, but not the monomeric ones, as was shown by FTRaman spectroscopy and TPR in H 2 . Monolayer vanadia species (monomeric and polymeric) are responsible for the catalytic activity and selectivity to benzaldehyde and benzoic acid independently on the catalyst preparation method. Bulk V 2 O 5 and TiO 2 are considerably less active. Therefore, an increase of the vanadium concentration in the samples above the monolayer coverage results in a decrease of the specific rate in toluene oxidation due to the partial blockage of active monolayer species by bulk crystalline V 2 O 5 . Potassium diminishes the catalyst acidity resulting in a decrease of the total rate of toluene oxidation and suppression of deactivation. Deactivation due to coking is probably related to the Brønsted acid sites associated with the bridging oxygen in the polymeric species and bulk V 2 O 5 . Doping by K diminishes the amount of active monolayer vanadia leading to the formation of non-active K-doped monomeric vanadia species and KVO 3 . # 2004 Elsevier B.V. All rights reserved.

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Section: Discussionsupporting

confidence: 92%

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

2004

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“…Table 2 lists the surface density of each metal oxide existing in the unpromoted and promoted catalysts that was estimated using its amount and their S BET value given in Table 1. Calculations of the surface coverage based on monolayer coverage of each metal oxide reported in the literature [60][61][62][63][64][65][66] are also provided in Table 2. Both VO x and FeO x were below monolayer coverage irrespective of the catalyst, but WO x in VWT, 2.73% Fe 2 O 3 /VWT and c-VWT could exceed the monolayer coverage, which is mainly due to a rather wide range of experimentally-determined WO x monolayer values, such as 4.6-7.0 µmol WO x /m 2 [60,61,63,65,66].…”

Section: Role Of Fe 2 O 3 Species For the Suppression Of N 2 O Formationmentioning

confidence: 99%

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

Kim

Yang

2018

Catalysts

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Promotion of 2.73% Fe 2 O 3 in an in-house-made V 2 O 5 -WO 3 /TiO 2 (VWT) and a commercial V 2 O 5 -WO 3 /TiO 2 (c-VWT) has been investigated as a cost effective approach to the suppression of N 2 O formation in the selective catalytic reduction of NO by NH 3 (NH 3 -SCR). The promoted VWT and c-VWT catalysts all gave a significantly decreased N 2 O production at temperatures >400 • C compared to the unpromoted samples. However, such a promotion led to the loss in high temperature NO conversion, mainly due to the oxidation of NH 3 to N-containing gases, particularly NO. Characterization of the unpromoted and promoted catalysts using X-ray diffraction (XRD), NH 3 adsorption-desorption, and Raman spectroscopy techniques could explain the reason why the promotion showed much lower N 2 O formation levels at high temperatures. The addition of Fe 2 O 3 to c-VWT resulted in redispersion of the V 2 O 5 species, although this was not visible for 2.73% Fe 2 O 3 /VWT. The iron oxides exist as a highly-dispersed noncrystalline α-Fe 2 O 3 in the promoted catalysts. These Raman spectra had a new Raman signal that could be tentatively assigned to Fe 2 O 3 -induced tetrahedrally coordinated polymeric vanadates and/or surface V-O-Fe species with significant electronic interactions between the both metal oxides. Calculations of the monolayer coverage of each metal oxide and the surface total coverage are reasonably consistent with Raman measurements. The proposed vanadia-based surface polymeric entities may play a key role for the substantial reduction of N 2 O formed at high temperatures by NH 3 species adsorbed strongly on the promoted catalysts. This reaction is a main pathway to greatly suppress the extent of N 2 O formation in NH 3 -SCR reaction over the promoted catalysts.

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“…Many authors have used a solution of VOCl 3 in CCl 4 or in benzene to obtain a dispersed VO x phase on various inorganic oxides [149]. Non-aqueous solutions of VO(O i Bu) 3 have also been successfully used [150][151][152][153]. Multiple grafting followed by calcination will result in a monolayer of vanadium oxides on the surface of a support oxide.…”

Section: Preparation Methods Of Supported Vanadium Oxide Catalystsmentioning

confidence: 99%

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

2003

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Supported vanadium oxide catalysts are active in a wide range of applications. In this review, an overview is given of the current knowledge available about vanadium oxide-based catalysts. The review starts with the importance of vanadium in heterogeneous catalysis, a discussion of the molecular structure of vanadium in water and in the solid state and an overview of the spectroscopic techniques enabling to study the chemistry of supported vanadium oxides. In the second part, it will be shown that advanced spectroscopic tools can be used to obtain detailed information about the coordination environment and oxidation state of vanadium oxides during each stage of the life-span of a heterogeneous catalyst. Three topics will be discussed: (1) the molecular structure of supported vanadium oxide catalysts under hydrated, dehydrated and reduced conditions, including the parameters, which influence the molecular structures formed at the surface of the support oxide; (2) elucidation of the active surface vanadium oxide during the oxidation of methanol to formaldehyde, the reaction mechanism and the vanadium oxide-support effect; and (3) deactivation of fluid catalytic cracking (FCC) catalysts by migration of vanadium oxides and the development of a method preventing the structural breakdown of zeolites by trapping the mobile vanadium oxides in an aluminum oxide coating.

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Reactivity of V2O5Catalysts for the Selective Catalytic Reduction of NO by NH3: Influence of Vanadia Loading, H2O, and SO2

Cited by 258 publications

References 0 publications

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

Partial oxidation of toluene to benzaldehyde and benzoic acid over model vanadia/titania catalysts: role of vanadia species

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

Chemistry, spectroscopy and the role of supported vanadium oxides in heterogeneous catalysis

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