Effect of Catalyst Placement on the Plasma-Catalytic Oxidation of NO

Jõgi, Indrek; Levoll, Erik; Raud, Jüri

doi:10.1007/s10562-016-1953-9

Cited by 7 publications

(5 citation statements)

References 27 publications

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“…This can be explained by the NO 2 adsorption on the metaloxide surface and the production of surface bound NO 3 and gas phase NO. At the beginning of direct plasma treatment in the presence of catalyst [87], both NO and NO 2 concentrations remain below the equilibrium value reached after several minutes of reactors work. This suggests that there has to be additional channel for NO removal from the gas phase which is most likely the reaction with surface bound oxygen species.…”

Section: = -D [ ] ([ ] [ ]) Resulting In the Relationmentioning

confidence: 90%

“…The back-reaction in the gas phase still limits the oxidation efficiency. Furthermore, only the part of catalyst which is placed at the outlet of reactor has an influence on the NO oxidation [87]. As a downside, the slow reaction between ozone and hydrocarbons prevents the production of partially oxidized hydrocarbons which have been found to be beneficial for SCR [88].…”

Section: = -D [ ] ([ ] [ ]) Resulting In the Relationmentioning

confidence: 99%

“…The investigation involved stationary and timedependent studies of NOx oxidation with different configurations of plasma and catalyst placement at varying experimental conditions. Furthermore, analytical lumped kinetic models incorporating effective reaction coefficients for NOx oxidation were derived to quantify the effect of catalyst at different experimental conditions [3,4]. The results were mostly obtained in dry O2:N2 mixtures.…”

Section: Introductionmentioning

confidence: 99%

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Plasma and catalyst for the oxidation of NOx

Jõgi

Erme

Levoll

et al. 2018

Plasma Sources Sci. Technol.

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Efficient exhaust gas cleaning from NO x (NO and NO 2 ) by absorption and adsorption based methods requires the oxidation of NO. The application of non-thermal plasma is considered as a promising oxidation method but the oxidation of NO by direct plasma remains limited due to the back-reaction of NO 2 to NO mediated by O radicals in plasma. Indirect NO oxidation by plasma produced ozone allows to circumvent the back-reaction and further oxidize NO 2 to N 2 O 5 but the slow reaction rate for the latter process limits the efficiency of this process. Present paper gives an overview of the role of metal-oxide catalysts in the improvement of oxidation efficiency for both direct and indirect plasma oxidation of NO x . The plasma produced active oxygen species (O, O 3 ) were shown to play an important role in the reactions taking place on the catalyst surfaces while the exact mechanism and extent of the effect were different for direct and indirect oxidation. In the case of direct plasma oxidation, both short and long lifetime oxygen species could reach the catalyst and participate in the oxidation of NO to NO 2 . The back-reaction in the plasma phase remained still important factor and limited the effect of catalyst. In the case of indirect oxidation, only ozone could reach the catalyst surface and improve the oxidation of NO 2 to N 2 O 5 . The effect of catalyst at different experimental conditions was quantitatively described with the aid of simple global chemical kinetic models derived for the NO x oxidation either by plasma or ozone. The models allowed to compare the effect of different catalysts and to analyze the limitations for the efficiency improvement by catalyst.

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Section: = -D [ ] ([ ] [ ]) Resulting In the Relationmentioning

confidence: 90%

Section: = -D [ ] ([ ] [ ]) Resulting In the Relationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plasma and catalyst for the oxidation of NOx

Jõgi

Erme

Levoll

et al. 2018

Plasma Sources Sci. Technol.

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“…Without the catalyst, NO was oxidized to NO 2 in the discharge zone and, on increasing the NO 2 concentration in the bed, the reverse reaction occurred until the reaction reached equilibrium. If the catalyst was placed in the inlet of the discharge zone, the NO 2 formed via the catalyst was converted back to NO by the end of the reactor where no catalyst was present [44].…”

Section: No Oxidation Using Non-thermal Plasma-catalyst Systemmentioning

confidence: 99%

Non-thermal-plasma-activated de-NO _x catalysis

Gholami

Stere

Goguet

et al. 2017

Phil. Trans. R. Soc. A.

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The combination of non-thermal plasma (NTP) with catalyst systems as an alternative technology to remove NO x emissions in the exhaust of lean-burn stationary and mobile sources is reviewed. Several factors, such as low exhaust gas temperatures (below 300°C), low selectivity to N 2 and the presence of impurities, make current thermally activated technologies inefficient. Various hybrid plasma–catalyst systems have been examined and shown to have a synergistic effect on de-NO x efficiency when compared with NTP or catalyst-alone systems. The NTP is believed to form oxygenated species, such as aldehydes and nitrogen-containing organic species, and to convert NO to NO 2 , which improves the reduction efficiency of N 2 during hydrocarbon-selective catalytic reduction reactions. The NTP has been used as a pretreatment to convert NO to its higher oxidation states such as NO 2 to improve NO x reduction efficiency in the subsequent processes, e.g. NH 3 -selective catalytic reduction. It has been applied to the lean phase of the NO x storage to improve the adsorption capacity of the catalyst by conversion of NO to NO 2 . Alternatively, a catalyst with high adsorption capacity is chosen and the NTP is applied to the rich phase to improve the reduction activity of the catalyst at low temperature. This article is part of a discussion meeting issue ‘Providing sustainable catalytic solutions for a rapidly changing world’.

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“…This result differs from the NO oxidation on the TiO 2 surface in the presence of direct plasma, in which catalytic oxidation occurred because of the O radicals produced in the plasma. 40 Surface Processes in the N 2 O 5 Production Regime. To account for the influence of TiO 2 in the N 2 O 5 production regime ([O 3 ] in > [NO] in ), we have proposed that the process is enhanced by the catalytic decomposition of ozone, which is enabled by the existence of surplus ozone from the fast gasphase oxidation of NO to NO 2 .…”

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Adsorption of Nitrogen Oxides on TiO₂ Surface as a Function of NO₂ and N₂O₅ Fraction in the Gas Phase

2018

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The present study was devoted to the investigation of adsorption of nitrogen oxides on TiO, with the focus on the effect of NO concentration, composition, and flow rate. The inlet NO with a concentration of 200-800 ppm in pure N was mixed with ozone, produced from pure oxygen, and directed to a reactor with catalytic TiO powder. The oxidation of NO by ozone allowed to prepare mixtures with variable concentrations of NO and NO or NO and NO which were adsorbed on the catalyst surface during the oxidation phase and were desorbed when only NO was flowing through the reactor. Diffuse reflectance infrared Fourier transform spectroscopy studies showed NO as the main adsorbed nitrogen oxide specimen on the surface. The amount of adsorbed nitrogen oxide species increased with the increasing fraction of NO in the gas phase and was inversely proportional with the gas-phase NO concentration. An important finding was the abrupt increase in the nitrogen oxide adsorption capacity of TiO when the inlet concentration of ozone became sufficiently large to oxidize NO to NO. On the basis of the results, a model of the surface processes is proposed, involving the production of NO and NO on the surface of TiO.

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Effect of Catalyst Placement on the Plasma-Catalytic Oxidation of NO

Cited by 7 publications

References 27 publications

Plasma and catalyst for the oxidation of NOx

Plasma and catalyst for the oxidation of NOx

Non-thermal-plasma-activated de-NO _x catalysis

Adsorption of Nitrogen Oxides on TiO₂ Surface as a Function of NO₂ and N₂O₅ Fraction in the Gas Phase

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Effect of Catalyst Placement on the Plasma-Catalytic Oxidation of NO

Cited by 7 publications

References 27 publications

Plasma and catalyst for the oxidation of NOx

Plasma and catalyst for the oxidation of NOx

Non-thermal-plasma-activated de-NO x catalysis

Adsorption of Nitrogen Oxides on TiO2 Surface as a Function of NO2 and N2O5 Fraction in the Gas Phase

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Product

Resources

About

Non-thermal-plasma-activated de-NO _x catalysis

Adsorption of Nitrogen Oxides on TiO₂ Surface as a Function of NO₂ and N₂O₅ Fraction in the Gas Phase