Mechanisms and kinetics of SO2 adsorption and NOx reduction on active coke

Richter, Ekkehard; Knoblauch, K.; Jüntgen, H.

doi:10.1016/0950-4214(87)80007-5

Cited by 41 publications

(17 citation statements)

References 3 publications

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“…The diesel soot samples with a lower SCR activity evolved greater amounts of HNO 3 because it was not consumed in the further SCR process. Therefore, a mechanism that excludes NH 4 NO 3 , such as that proposed by Richter et al and Juntgen et al, 14,15 can probably be excluded for the soot samples used in the present study. Furthermore, the observed HNO 3 emissions led to the conclusion that the disproportionation step 12 does not limit the SCR reaction and that the presence of adsorption sites for NH 3 is likely the limiting factor.…”

Section: Mechanismmentioning

confidence: 92%

Selective Catalytic Reduction of NO_x with Ammonia over Soot

2012

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The selective catalytic reduction (SCR) of nitrogen oxides (NO x ) in the presence of NH 3 was investigated on Printex U and three diesel soot samples in the temperature range between 200 and 350°C. In the presence of NO + NO 2 , a stoichiometry similar to that of the fast SCR reaction was observed, whereas in the absence of NO, the stoichiometry shifted to values typical of the NO 2 SCR reaction. In the presence of only NO, no NO x reduction was observed. Carbon oxidation and SCR reaction minimally influenced each other. On the basis of these experimental results, a mechanism for NO x reduction over diesel soot was developed. The first step in the reaction is the disproportionation of NO 2 , which is followed by the formation of ammonium nitrates and nitrites. The nitrites decompose directly into N 2 and H 2 O, whereas the nitrates have to be reduced to nitrites either by NO or in its absence by NH 3 , which also leads to the formation of N 2 and H 2 O. The observed byproducts indicated that the acidity and the amount of surface functional groups for NH 3 are important preconditions for the occurrence of the SCR reaction over soot.

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Section: Mechanismmentioning

confidence: 92%

Selective Catalytic Reduction of NO_x with Ammonia over Soot

2012

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“…In a preliminary experiment we tested Printex U for its SCR activity under conditions similar to previous studies in the 1980s on activated carbon [5][6][7][8][9][10][11][12][13][14]24]. However, at a GHSV of 3,000 h -1 no NO x reduction activity was observed for Printex U with NH 3 when NO x was only NO.…”

Section: Scr Reaction Over Printex U In the Presence Of No And Nhmentioning

confidence: 92%

“…For special low temperature applications at 100-150°C, activated carbon catalysts were developed for the reduction of NO at space velocities of approx. 2,000 h -1 in the 1970s and 1980s [5][6][7][8][9][10][11][12][13][14]. The up to 80 % conversion reached with these catalysts strongly depends on the carbon type and pre-treatment [8].…”

Section: Introductionmentioning

confidence: 98%

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Diesel Soot Catalyzes the Selective Catalytic Reduction of NOx with NH3

2013

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The catalytic activity of soot samples for the selective catalytic reduction (SCR) of NO x with NH 3 was investigated in dependence of the NO 2 , NO and NH 3 concentration in the temperature range between 200 and 350°C. The highest NO x reduction of up to 25 % was measured in the presence of both NO 2 and NO at a GHSV of 35,000 h-1. Decreasing space velocities resulted in an increase of the SCR activity. In the absence of NO 2 , NO x reduction was not observed. Carbon oxidation and SCR reaction occurred in parallel due to the presence of NO 2 and O 2 , but hardly influenced each other, which suggested that in the NO x reduction on soot most probably physisorbed species were involved. The observed stoichiometries indicated the action of the fast SCR reaction in the presence of NO and the NO 2 SCR reaction in the absence of NO, while the observed gas phase and surface species pointed at reaction steps similar to those on classical SCR catalysts.

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“…The origin of the carbon has been demonstrated to be important for SCR activity and stability of the carbon catalyst [l9]. The presence of heteroatoms like oxygen and nitrogen also influences SCR activity [14,18,20]. Even a crude linear correlation has been reported [21] between the active surface area (ASA) and SCR activity of some high-temperature carbon samples prepared from oxidized bituminous carbon, although no conclusive relationship was found.…”

Section: Introductionmentioning

confidence: 99%

Selective catalytic reduction of no with NH3 over activated carbons. I: Effect of origin and activation procedure on activity

Martín-Martínez

Singoredjo

Mittelmeijer‐Hazeleger

et al. 1994

Carbon

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General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Vol. 32, NO. 5, pp. 897-904, 1994 Abstract-The activity for the selective catalytic reduction of NO with NH? (SCR) of a suite of different activated carbons has been studied in the temperature range 373-550 K. The effect of origin (bituminous coal, peat, plum stones, and olive pits), activation agent (steam, CO*), and degree of activation was investigated by activity measurements. In general, the SCR activity, which is relatively high at 373 K, decreases with increasing temperature, and for some carbons increases again above 450 K. Two types of SCR processes are operative. In the lower temperature range, the narrow microporosity affects the rate by increased adsorption of NO, resulting in higher local concentrations. In the higher temperature range, oxygen functional groups determine the SCR activity level. Precursors yielding narrow microporous carbons result in better activities below 450 K. Steam-activated carbons gave higher SCR activity above 450 K than CO?-activated carbons.

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Mechanisms and kinetics of SO2 adsorption and NOx reduction on active coke

Cited by 41 publications

References 3 publications

Selective Catalytic Reduction of NO_x with Ammonia over Soot

Selective Catalytic Reduction of NO_x with Ammonia over Soot

Diesel Soot Catalyzes the Selective Catalytic Reduction of NOx with NH3

Selective catalytic reduction of no with NH3 over activated carbons. I: Effect of origin and activation procedure on activity

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Mechanisms and kinetics of SO2 adsorption and NOx reduction on active coke

Cited by 41 publications

References 3 publications

Selective Catalytic Reduction of NOx with Ammonia over Soot

Selective Catalytic Reduction of NOx with Ammonia over Soot

Diesel Soot Catalyzes the Selective Catalytic Reduction of NOx with NH3

Selective catalytic reduction of no with NH3 over activated carbons. I: Effect of origin and activation procedure on activity

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Selective Catalytic Reduction of NO_x with Ammonia over Soot

Selective Catalytic Reduction of NO_x with Ammonia over Soot