Oxidation of sulfur dioxide to sulfur trioxide over honeycomb DeNoxing catalysts

Švachula, J.; Alemany, Luı́s J.; Ferlazzo, N.; Forzatti, Pio; Tronconi, Enrico; Bregani, F.

doi:10.1021/ie00017a009

Cited by 128 publications

(99 citation statements)

References 14 publications

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“…Measurements of sulfate formation versus NH 3 /NO ratio, at 1 to 2.2 ppmv HCl and 10 to 12 ppmv HCl suggested that conversion of SO 2 to sulfate was highest in the absence of NH 3 and decreased with increasing NH 3 /NO ratio and with increasing HCl, in contrast to the observation regarding dependence on HCl just above. Promotion of SO 2 oxidation in the complete absence of NH 3 , and the gradual decline in SO 2 oxidation with increasing NH 3 /NO ratio, are both consistent with observations reported by Svachula et al (1993) and Gale et al (2006b).…”

Section: Mercury and Sulfur Dioxide Oxidation During Selective Catalysupporting

confidence: 91%

“…Promotion of SO 2 oxidation in the complete absence of NH 3 , and the decline in SO 2 oxidation with increasing NH 3 /NO ratio, are both consistent with observations reported by Svachula et al (1993) and Gale et al (2006b). The sulfate measurements in the presence of 10 ppmv HCl, in the range of NH 3 /NO ratio from 0.75 to 1.15, are close to the detection limit of the controlled condensation procedure (Section 2.2.5).…”

Section: Sulfate Formationsupporting

confidence: 91%

“…The calculations were performed for 1 and 10 ppmv HCl in the presence of 300 ppmv NO and 877 ppmv SO 2 at the catalyst inlet, with no influence from CO. The calculated dependence of SO 3 formation on NH 3 /NO ratio is in satisfactory agreement with the measurements of sulfate at both the intermediate (10 to 12 ppmv) and low (1 to 2.2 ppmv) HCl levels, with the exception of the measurements at high NH 3 /NO ratio in the presence of 10 to 12 ppmv HCl, near the detection limit of the controlled condensation procedure, and the measurements at NH 3 /NO = 0, where the promotion of SO 3 formation by NO is greatest, a component of the rate expression of Svachula et al (1993) not included in the calculations. We also note: (1) that sulfate formation in the reactor containing sand is approximately the same as sulfate formation in the SCR catalyst in the presence of NH 3 /NO at the catalyst inlet from 0.91 to 0.95 and HCl from 1 to 2.2 ppmv, and (2) that the single measurement at 49 ppmv HCl (open square symbol at the upper right) does not follow the trend established by the measurements at 1 to 2.2 and 10 to 12 ppmv HCl (sulfate formation decreasing with increasing HCl).…”

Section: Sulfur Dioxide Oxidation To Sulfatementioning

confidence: 92%

“…The presence of NO in the absence of NH 3 is a condition that would exist if flue gas were passed through an SCR catalyst when NH 3 addition is not required for NO X reduction to meet air quality regulations. However, sulfate formation is also enhanced by NO in the absence of NH 3 (Svachula et al, 1993).…”

Section: Mercury and Sulfur Dioxide Oxidation During Selective Catalymentioning

confidence: 96%

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Oxidation of Mercury in Products of Coal Combustion

Walsh¹,

Tong²,

Bhopatkar³

et al. 2009

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________________________________________________________________________Laboratory measurements of mercury oxidation during selective catalytic reduction (SCR) of nitric oxide, simulation of pilot-scale measurements of mercury oxidation and adsorption by unburned carbon and fly ash, and synthesis of new materials for simultaneous oxidation and adsorption of mercury, were performed in support of the development of technology for control of mercury emissions from coal-fired boilers and furnaces.Conversion of gas-phase mercury from the elemental state to water-soluble oxidized form (HgCl 2 ) enables removal of mercury during wet flue gas desulfurization. The increase in mercury oxidation in a monolithic V 2 O 5 -WO 3 /TiO 2 SCR catalyst with increasing HCl at low levels of HCl (< 10 ppmv) and decrease in mercury oxidation with increasing NH 3 /NO ratio during SCR were consistent with results of previous work by others. The most significant finding of the present work was the inhibition of mercury oxidation in the presence of CO during SCR of NO at low levels of HCl. In the presence of 2 ppmv HCl, expected in combustion products from some Powder River Basin coals, an increase in CO from 0 to 50 ppmv reduced the extent of mercury oxidation from 24 ± 3 to 1 ± 4%. Further increase in CO to 100 ppmv completely suppressed mercury oxidation. In the presence of 11-12 ppmv HCl, increasing CO from 0 to ~120 ppmv reduced mercury oxidation from ~70% to 50%. Conversion of SO 2 to sulfate also decreased with increasing NH 3 /NO ratio, but the effects of HCl and CO in flue gas on SO 2 oxidation were unclear.Oxidation and adsorption of mercury by unburned carbon and fly ash enables mercury removal in a particulate control device. A chemical kinetic mechanism consisting of nine homogeneous and heterogeneous reactions for mercury oxidation and removal was developed to interpret pilot-scale measurements of mercury oxidation and adsorption by unburned carbon and fly ash in experiments at pilot scale, burning bituminous coals (Gale, 2006) and blends of bituminous coals with Powder River Basin coal (Gale, 2005). The removal of mercury by fly ash and unburned carbon in the flue gas from combustion of the bituminous coals and blends was reproduced with satisfactory accuracy by the model. The enhancement of mercury capture in the presence of calcium (Gale, 2005) explained a synergistic effect of blending on mercury removal across the baghouse. The extent of mercury oxidation, on the other hand, was not so well described by the simulation, because of oversensitivity of the oxidation process in the model to the concentration of unburned carbon.Combined catalysts and sorbents for oxidation and removal of mercury from flue gas at low temperature were based on surfactant-templated silicas containing a transition metal and an organic functional group. The presence of both metal ions and organic groups within the pore structure of the materials is expected to impart to them the ability to simultaneously oxidize elemental mercury and adso...

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Section: Mercury and Sulfur Dioxide Oxidation During Selective Catalysupporting

confidence: 91%

Section: Sulfate Formationsupporting

confidence: 91%

Section: Sulfur Dioxide Oxidation To Sulfatementioning

confidence: 92%

Section: Mercury and Sulfur Dioxide Oxidation During Selective Catalymentioning

confidence: 96%

See 2 more Smart Citations

Oxidation of Mercury in Products of Coal Combustion

Walsh¹,

Tong²,

Bhopatkar³

et al. 2009

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“…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 2 O 5 loadings in the SCR catalyst; 3,8 however, the content of V 2 O 5 is limited to less than 2 wt% to avoid the production of SO 3 and because higher loadings of V 2 O 5 decreases the temperature at which the TiO 2 anatase-to-rutile phase transformation occurs. 9 This phase transformation leads to a decrease in the surface area and the catalyst activity.…”

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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Nitrogen Oxides Removal – Industrial

Forzatti¹,

Lietti²,

Tronconi³

2002

Encyclopedia of Catalysis

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The heterogeneous selective catalytic reduction (SCR) of NO x by NH 3 from stationary sources is addressed in this review. The typical commercial De‐NO x SCR catalysts are presented, along with their performances in both the NO x reduction and the SO 2 oxidation reactions. Mechanistic and kinetic aspects of the reactions involved in the SCR process, the reactor and process configurations, and the design and modeling of the SCR systems are also illustrated.

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Oxidation of sulfur dioxide to sulfur trioxide over honeycomb DeNoxing catalysts

Cited by 128 publications

References 14 publications

Oxidation of Mercury in Products of Coal Combustion

Oxidation of Mercury in Products of Coal Combustion

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

Nitrogen Oxides Removal – Industrial

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Oxidation of sulfur dioxide to sulfur trioxide over honeycomb DeNoxing catalysts

Cited by 128 publications

References 14 publications

Oxidation of Mercury in Products of Coal Combustion

Oxidation of Mercury in Products of Coal Combustion

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

Nitrogen Oxides Removal – Industrial

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Product

Resources

About

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