The role of tungsten in formation of active sites for no SCR on the V-W-O catalyst surface — quantum chemical modeling (DFT)

Brocławik, Ewa; Góra, Artur; Najbar, M.

doi:10.1016/s1381-1169(00)00462-3

Cited by 44 publications

(27 citation statements)

References 30 publications

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“…The interaction between surface vanadia and tungsten species has been modeled using cluster approaches 11,26 but neglect to include the strong interaction between the two active phases and the support. 3 This ternary system follows a structure similar to that of the binary system (V 2 O 5 −TiO 2 ).…”

Section: ■ Introductionmentioning

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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Section: ■ Introductionmentioning

confidence: 99%

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

2013

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“…Therefore, in this paper vanadia and molybdena-vanadia solid solution surfaces are modeled by one-layer clusters embedded in a set of point charges in order to include electrostatic bulk influence. Such a onelayer model of the surface has often been used in literature for vanadia and the binary systems based on vanadia structure [12,30,31,33,47,50,51,52,54]. However, a quantitative description of the adsorption processes may require inclusion of the second layer in the cluster.…”

Section: Models and Computational Detailsmentioning

confidence: 99%

“…In those studies both, semi-empirical [29,30,[34][35][36]39,42,48], and ab initio (HF and DFT) [12,[17][18][19][20][21][22][23][24][25][26][27][28][30][31][32][33][37][38][39][40][41][42][43][44][45][46][47][49][50][51][52][53][54][55][56][57] quantum-chemical approaches were used. Cluster models of the surfaces [12,[54][55][56][57] [24][25]<...>…”

Section: Introductionmentioning

confidence: 99%

“…Cluster models of the surfaces [12,[54][55][56][57] [24][25][26]37,42,53] were applied. The theoretical investigations focused on the properties of the oxide systems [12,[24][25][26][27][28][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]50,52,54,57] as well as the reactions that occur on their surfaces, e.g. adsorption of H, H + [30,31,34,35,[37][38][39][40][41]43,44,48,…”

Section: Introductionmentioning

confidence: 99%

“…In [12,47,[50][51][52]54], the studies on the V-O-W properties as well as the water adsorption [50,52,54] and dissociation [51,52,54] were reported. The effects of additives on the electronic and geometric structure of the active center of a vanadia-based catalyst for oxidative dehydrogenation of propane have been presented [57].…”

Section: Introductionmentioning

confidence: 99%

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The role of tungsten in formation of active sites for no SCR on the V-W-O catalyst surface — quantum chemical modeling (DFT)

Cited by 44 publications

References 30 publications

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

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

A comparison of the electronic structure and NO adsorption on the (001)-V2O5 surfaces and (001)-V2O5 surfaces with Mo defects—DFT cluster studies

Environmental Catalysis: Stationary Sources

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The role of tungsten in formation of active sites for no SCR on the V-W-O catalyst surface — quantum chemical modeling (DFT)

Cited by 44 publications

References 30 publications

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

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

A comparison of the electronic structure and NO adsorption on the (001)-V2O5 surfaces and (001)-V2O5 surfaces with Mo defects—DFT cluster studies

Environmental Catalysis: Stationary Sources

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

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