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

Journal Article · · Applied Catalysis. B, Environmental
 [1];  [1];  [1];  [2];  [2];  [2]
  1. Institute of Chemical Technology, Prague (Czech Republic)
  2. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
+ Show Author Affiliations
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.
Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Vehicle Technologies Office; Czech Ministry of Education
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1286844
Alternate ID(s):
OSTI ID: 1249890
Journal Information:
Applied Catalysis. B, Environmental, Journal Name: Applied Catalysis. B, Environmental Vol. 166-167; ISSN 0926-3373
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
54 ENVIRONMENTAL SCIENCES
N2 formation
N2O formation
NOx reduction
NOx storage catalyst
exhaust gas aftertreatment