Reactivity and Physicochemical Characterization of V2O5-WO3/TiO2 De-NO  Catalysts

Alemany, Luı́s J.; Lietti, Luca; Ferlazzo, N.; Forzatti, Pio; Busca, Guido; Giamello, Elio; Bregani, F.

doi:10.1006/jcat.1995.1193

Cited by 364 publications

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“…% is often chosen for stationary applications, where the volume of the catalytic converter and the activity are not key properties. Instead, sulfur resistance, longevity and production costs are of higher significance [24]. In mobile sources, V-based catalysts need to be highly active due to the limited available space for the exhaust gas treatment system.…”

Section: Introductionmentioning

confidence: 99%

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

et al. 2015

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V2O5/WO3-TiO2 selective catalytic reduction (SCR) catalysts with a V2O5 loading of 1.7, 2.0, 2.3, 2.6, 2.9, 3.2 and 3.5 wt. % were investigated in the fresh state and after hydrothermal aging at 600 °C for 16 h. The catalysts were characterized by means of nitrogen physisorption, X-ray diffraction and X-ray absorption spectroscopy. In the fresh state, the SCR activity increased with increasing V loading. Upon aging, the catalysts with up to 2.3 wt. % V2O5 exhibited higher NOx reduction activity than in the fresh state, while the catalysts with more than 2.6 wt. % V2O5 showed increasing deactivation tendencies. The observed activation and deactivation were correlated with the change of the VOx and WOx surface coverages. Only catalysts with a VOx coverage below 50% in the aged state did not show deactivation tendencies. With respect to tungsten, above one monolayer of WOx, WO3 particles were formed leading to loss of surface acidity, sintering, catalyst deactivation and early NH3 slip. An optimal compromise between activity and hydrothermal aging resistance could be obtained only with V2O5 between 2.0 and 2.6 wt. %.

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Section: Introductionmentioning

confidence: 99%

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

et al. 2015

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“…Promoting its oxidation along the path of the flue gas from the boiler to the stack is the best removal strategy using current emission control technologies. Mercury oxidation has been observed across the selective catalytic reduction (SCR) unit with a primary purpose of controlling NO x emissions by reducing them to N 2 and water vapor using ammonia (NH 3 ). Employing an already existing air pollution control device such as the SCR unit to tackle the Hg problem is an attractive approach due to the lower economic invesment and the environmental and heath benefits of reducing Hg emissions.…”

Section: ■ Introductionmentioning

confidence: 99%

“…3,11,12 The commercial composition of the SCR is <2 wt% of vanadia oxide, 10 wt % of tungsten oxide supported on anatase, TiO 2 . However, this is the composition for an optimal performance of this catalyst toward NO x reduction, and little is known about the optimal composition for Hg oxidation (i.e., Hg 0 oxidation).…”

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confidence: 99%

Role of WO₃ in the Hg Oxidation across the V₂O₅–WO₃–TiO₂ SCR Catalyst: A DFT Study

2013

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Selective catalytic reduction (SCR) units can be exploited to reduce Hg emissions from coal-based power plants; hereby, Hg 0 is oxidized into Hg 2+ , which has a higher solubility than the former and can therefore be scrubbed before leaving the stacks. With the purpose of examining the effect of the surface composition and surface coverage on the reactivity of a commercial SCR catalyst (V 2 O 5 −WO 3 −TiO 2 ) toward Hg oxidation, two models were used to represent TiO 2 -supported systems with low and high loading of the two active phases (i.e., V 2 O 5 and WO 3 ). The reactivities of these systems were compared through the analysis of the adsorption energies of Hg, Cl• , HgCl, and HCl, which are likely involved in the Hg oxidation mechanism. These adsorption energies were complemented by results from both the Bader charge and projected density of states (PDOS) analyses, thus providing an increased understanding of the effects of surface coverage and composition on the electronic structure of these materials. An enhanced reactivity of the SCR catalyst is observed with increasing loadings of both V 2 O 5 and WO 3 phases. Binary systems (i.e., V 2 O 5 −TiO 2 or WO 3 −TiO 2 ) were compared against ternary systems (V 2 O 5 −WO 3 −TiO 2 with different V 2 O 5 /WO 3 ratios) and indicate a higher reactivity of the latter. ■ INTRODUCTIONThe annual estimation of Hg emission from natural and coalfired power plants in the United States corresponds to 48 tons, about one-third of the total amount of mercury released by anthropogenic sources of this country.1 As the environmental and health problems associated with the mercury emissions from stationary sources become an obvious problem, the U.S. Environment Protection Agency set in 2011 a series of emission standards to limit these emissions. These standards state that the U.S. natural gas and coal-fired power plants are forced to install air pollution control devices to prevent 91% of the Hg present in flue gas from being released. 2The insolubility and inertness of Hg 0 make its capture difficult. Promoting its oxidation along the path of the flue gas from the boiler to the stack is the best removal strategy using current emission control technologies. Mercury oxidation has been observed across the selective catalytic reduction (SCR) unit with a primary purpose of controlling NO x emissions by reducing them to N 2 and water vapor using ammonia (NH 3 ). Employing an already existing air pollution control device such as the SCR unit to tackle the Hg problem is an attractive approach due to the lower economic invesment and the environmental and heath benefits of reducing Hg emissions.Commercial SCR catalysts employ the anatase phase of TiO 2 as a support material for the active phases which consists of vanadium and tungsten oxides.3,4 The vanadia phase V 2 O 5 not only catalyzes NO x reduction 5 and Hg 0 oxidation 6 but also the undesired SO 2 to SO 3 oxidation reaction.7 It has been proven experimentally that higher catalytic activities are reached with increasing V ...

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“…Varios trabalhos afirmam que a forma anatasio favorece a dispersao e a formayao de grupos vanadis [7,11,16].…”

Section: Secagem Supercriticaunclassified

“…Recentemente estes catalisadores tern sido testados, tambem, em rea90es para rem09ao de CO e NO dos produtos da combustao automotiva e industrial (catalisadores de exaustao) [6][7][8][9][10].…”

Section: Introduunclassified

Catalisadores de óxido de vanádio suportados sobre titânia obtidos pelo processo sol-gel: preparação e caracterização

Rodella¹

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Reactivity and Physicochemical Characterization of V2O5-WO3/TiO2 De-NO Catalysts

Cited by 364 publications

References 0 publications

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

Role of WO₃ in the Hg Oxidation across the V₂O₅–WO₃–TiO₂ SCR Catalyst: A DFT Study

Catalisadores de óxido de vanádio suportados sobre titânia obtidos pelo processo sol-gel: preparação e caracterização

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Reactivity and Physicochemical Characterization of V2O5-WO3/TiO2 De-NO Catalysts

Cited by 364 publications

References 0 publications

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

VOx Surface Coverage Optimization of V2O5/WO3-TiO2 SCR Catalysts by Variation of the V Loading and by Aging

Role of WO3 in the Hg Oxidation across the V2O5–WO3–TiO2 SCR Catalyst: A DFT Study

Catalisadores de óxido de vanádio suportados sobre titânia obtidos pelo processo sol-gel: preparação e caracterização

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Role of WO₃ in the Hg Oxidation across the V₂O₅–WO₃–TiO₂ SCR Catalyst: A DFT Study