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Title: Dynamics of N2 and N2O peaks during and after the regeneration of lean NOx trap

Abstract

We study the dynamics and selectivity of N2 and N2O formation during and after the regeneration of a commercial NOx storage catalyst containing Pt, Pd, Rh, Ba on Ce/Zr, Mg/Al and Al oxides was studied with high-speed FTIR and SpaciMS analyzers. The lean/rich cycling experiments (60 s/5 s and 60 s/3 s) were performed in the temperature range 200–400°C, using H2, CO, and C3H6 individually for the reduction of adsorbed NOx. Isotopically labeled 15NO was employed in combination with Ar carrier gas in order to quantify the N2 product by mass spectrometry. N2 and N2O products were formed concurrently. The primary peaks appeared immediately after the rich-phase inception, and tailed off with breakthrough of the reductant front (accompanied by NH3 product). Secondary N2 and N2O peaks appeared at the rich-to-lean transition as a result of reactions between surface-deposited reductants/intermediates (CO, HC, NH3, -NCO) and residual stored NOx. At 200–300 °C, up to 30% of N2 and 50% of N2O products originated from the secondary peaks. The N2O/N2 selectivity ratio as well as the magnitude of secondary peaks decreased with temperature and duration of the rich phase. Among the three reductants, propene generated secondary N2 peak up to the highest temperature.more » Lastly the primary N2 peak exhibited a broadened shoulder aligned with movement of reduction front from the zone where both NOx and oxygen were stored to the NOx-free zone where only oxygen storage capacity was saturated. N2 formed in the NOx-free zone originated from reaction of NH3 with stored oxygen, while N2O formation in this zone was very low.« less

Authors:
 [1];  [1];  [1];  [2];  [2];  [2]
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  1. Institute of Chemical Technology, Prague (Czech Republic)
  2. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Vehicle Technologies Office; Czech Ministry of Education; USDOE
OSTI Identifier:
1286844
Alternate Identifier(s):
OSTI ID: 1249890
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Applied Catalysis. B, Environmental
Additional Journal Information:
Journal Volume: 166-167; Journal ID: ISSN 0926-3373
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 54 ENVIRONMENTAL SCIENCES; 36 MATERIALS SCIENCE; NOx storage catalyst; NOx reduction; N2O formation; N2 formation; exhaust gas aftertreatment

Citation Formats

Mráček, David, Koci, Petr, Marek, Milos, Choi, Jae-Soon, Pihl, Josh A., and Partridge, Jr., William P. Dynamics of N2 and N2O peaks during and after the regeneration of lean NOx trap. United States: N. p., 2014. Web. doi:10.1016/j.apcatb.2014.12.002.
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Mráček, David, Koci, Petr, Marek, Milos, Choi, Jae-Soon, Pihl, Josh A., & Partridge, Jr., William P. Dynamics of N2 and N2O peaks during and after the regeneration of lean NOx trap. United States. https://doi.org/10.1016/j.apcatb.2014.12.002
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Mráček, David, Koci, Petr, Marek, Milos, Choi, Jae-Soon, Pihl, Josh A., and Partridge, Jr., William P. Thu . "Dynamics of N2 and N2O peaks during and after the regeneration of lean NOx trap". United States. https://doi.org/10.1016/j.apcatb.2014.12.002. https://www.osti.gov/servlets/purl/1286844.
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@article{osti_1286844,
title = {Dynamics of N2 and N2O peaks during and after the regeneration of lean NOx trap},
author = {Mráček, David and Koci, Petr and Marek, Milos and Choi, Jae-Soon and Pihl, Josh A. and Partridge, Jr., William P.},
abstractNote = {We study the dynamics and selectivity of N2 and N2O formation during and after the regeneration of a commercial NOx storage catalyst containing Pt, Pd, Rh, Ba on Ce/Zr, Mg/Al and Al oxides was studied with high-speed FTIR and SpaciMS analyzers. The lean/rich cycling experiments (60 s/5 s and 60 s/3 s) were performed in the temperature range 200–400°C, using H2, CO, and C3H6 individually for the reduction of adsorbed NOx. Isotopically labeled 15NO was employed in combination with Ar carrier gas in order to quantify the N2 product by mass spectrometry. N2 and N2O products were formed concurrently. The primary peaks appeared immediately after the rich-phase inception, and tailed off with breakthrough of the reductant front (accompanied by NH3 product). Secondary N2 and N2O peaks appeared at the rich-to-lean transition as a result of reactions between surface-deposited reductants/intermediates (CO, HC, NH3, -NCO) and residual stored NOx. At 200–300 °C, up to 30% of N2 and 50% of N2O products originated from the secondary peaks. The N2O/N2 selectivity ratio as well as the magnitude of secondary peaks decreased with temperature and duration of the rich phase. Among the three reductants, propene generated secondary N2 peak up to the highest temperature. Lastly the primary N2 peak exhibited a broadened shoulder aligned with movement of reduction front from the zone where both NOx and oxygen were stored to the NOx-free zone where only oxygen storage capacity was saturated. N2 formed in the NOx-free zone originated from reaction of NH3 with stored oxygen, while N2O formation in this zone was very low.},
doi = {10.1016/j.apcatb.2014.12.002},
journal = {Applied Catalysis. B, Environmental},
number = ,
volume = 166-167,
place = {United States},
year = {Thu Dec 04 00:00:00 EST 2014},
month = {Thu Dec 04 00:00:00 EST 2014}
}
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Journal Article:
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Publisher's Version of Record
https://doi.org/10.1016/j.apcatb.2014.12.002
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Cited by: 24 works
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Figures / Tables:

Table 1 Table 1 : Inlet gas composition.
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Works referenced in this record:

Overview of the Fundamental Reactions and Degradation Mechanisms of NOx Storage/Reduction Catalysts
journal, December 2004

  • Epling, William S.; Campbell, Larry E.; Yezerets, Aleksey
  • Catalysis Reviews, Vol. 46, Issue 2
  • DOI: 10.1081/CR-200031932

NOx adsorption study over Pt–Ba/alumina catalysts: FT-IR and pulse experiments
journal, March 2004

Study of the effect of Ba loading for catalytic activity of Pt–Ba/Al2O3 model catalysts
journal, October 2004

NOxStorage in Barium-Containing Catalysts
journal, April 1999

  • Fridell, Erik; Skoglundh, Magnus; Westerberg, Björn
  • Journal of Catalysis, Vol. 183, Issue 2
  • DOI: 10.1006/jcat.1999.2415

New insights on N2O formation pathways during lean/rich cycling of a commercial lean NOx trap catalyst
journal, August 2014

Effective Model for Prediction of N2O and NH3 Formation During the Regeneration of NO x Storage Catalyst
journal, March 2013

Ammonia is a hydrogen carrier in the regeneration of Pt/BaO/Al2O3 NOx traps with H2
journal, February 2007

NOx storage and reduction with H2 on Pt/BaO/Al2O3 monolith: Spatio-temporal resolution of product distribution
journal, December 2008

  • Clayton, Robert D.; Harold, Michael P.; Balakotaiah, Vemuri
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  • DOI: 10.1016/j.apcatb.2008.05.018

Dynamics and selectivity of NOx reduction in NOx storage catalytic monolith
journal, September 2008

NH3 formation and utilization in regeneration of Pt/Ba/Al2O3 NOx storage-reduction catalyst with H2
journal, September 2009

Isocyanate formation and reactivity on a Ba-based LNT catalyst studied by DRIFTS
journal, August 2013

Reaction Pathways in the Reduction of NO x Species by CO over Pt–Ba/Al2O3: Lean NO x Trap Catalytic Systems
journal, July 2009

New insights into the promoting effect of H2O on a model Pt/Ba/Al2O3 NSR catalyst
journal, June 2010

Experimental investigation of the reduction of NOx species by CO and H2 over Pt–Ba/Al2O3 lean NOx trap systems
journal, June 2010

Origin of double dinitrogen release feature during fast switching between lean and rich cycles for NO storage reduction catalysts
journal, August 2014

Studying the NO x -trap mechanism over a Pt-Rh/Ba/Al 2 O 3 catalyst by operando FT-IR spectroscopy
journal, January 2003

  • Lesage, T.; Verrier, C.; Bazin, P.
  • Phys. Chem. Chem. Phys., Vol. 5, Issue 20
  • DOI: 10.1039/B305874N

FTIR and Transient Reactivity Experiments of the Reduction by H2, CO and HCs of NO x Stored Over Pt–Ba/Al2O3 LNTs
journal, March 2013

The chemistry of DeNOx reactions over Pt/Al2O3: The oxime route to N2 or N2O
journal, October 2006

Global kinetic model for the regeneration of NOx storage catalyst with CO, H2 and C3H6 in the presence of CO2 and H2O
journal, September 2009

Elucidating NH3 formation during NOx reduction by CO on Pt–BaO/Al2O3 in excess water
journal, April 2012

Spatiotemporal distribution of NOx storage and impact on NH3 and N2O selectivities during lean/rich cycling of a Ba-based lean NOx trap catalyst
journal, April 2012

Modelling of a combined NOx storage and NH3-SCR catalytic system for Diesel exhaust gas aftertreatment
journal, June 2010

Coupled NOx storage and reduction and selective catalytic reduction using dual-layer monolithic catalysts
journal, June 2012

Development of Di-Air - A New Diesel deNOx System by Adsorbed Intermediate Reductants
journal, August 2011

  • Bisaiji, Yuki; Yoshida, Kohei; Inoue, Mikio
  • SAE International Journal of Fuels and Lubricants, Vol. 5, Issue 1
  • DOI: 10.4271/2011-01-2089

Fast lean-rich cycling for enhanced NOx conversion on storage and reduction catalysts
journal, August 2014

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    Figures / Tables found in this record:

    Table 1 (p. 4)table
    Figure 1 (p. 7)figure
    Figure 2 (p. 7)figure
    Figure 3 (p. 8)figure
    Figure 4 (p. 9)figure
    Figure 5 (p. 10)figure
    Figure 6 (p. 11)figure
    Figure 7 (p. 12)figure
    Figure 8 (p. 14)figure
    Figure 9 (p. 15)figure
    Figure 10 (p. 16)figure
    Figure 11 (p. 17)figure
    Figure 12 (p. 18)figure
    Figure 13 (p. 19)figure
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