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 Article · Sun Jan 01 04:00:00 EST 2012 · Catalysis Today

DOI:https://doi.org/10.1016/j.cattod.2011.11.007· OSTI ID:1038795

Choi, Jae-Soon ^[1]; Partridge, Jr, William P ^[1]; Pihl, Josh A ^[1]; Kim, Miyoung ^[1]; Koci, Petr ^[2]; Daw, C Stuart ^[1]

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1. ORNL
2. Institute of Chemical Technology, Prague, Czech Republic

We summarize results from an investigation of the spatiotemporal distribution of NO{sub x} storage and intermediate gas species in determining the performance of a fully formulated, Ba-based, lean NO{sub x} trap catalyst under lean/rich cycling conditions. By experimentally resolving spatiotemporal profiles of gas composition, we found that stored NO{sub x} was significantly redistributed along the monolith axis during the rich phase of the cycle by release and subsequent downstream re-adsorption. Sulfur poisoning of upstream NO{sub x} storage sites caused the active NO{sub x}-storage zone to be displaced downstream. This axial displacement in turn influenced rich-phase NO{sub x} release and re-adsorption. As sulfur poisoning increased, NH3 slip at the catalyst exit also increased due to its formation closer to the catalyst outlet and decreased exposure to downstream oxidation by surface oxygen. N{sub 2}O formation was found to be associated with nitrate reduction rather than oxidation of NH3 by stored oxygen. We propose that the observed evolution of N{sub 2}O selectivity with sulfation can be explained by changes in the spatiotemporal distribution of NO{sub x} storage resulting in either increased or decreased number of precious-metal sites surrounded by nitrates.

• Research Organization: Oak Ridge National Laboratory (ORNL); Fuels, Engines and Emissions Research Center; National Transportation Research Center
• Sponsoring Organization: EE USDOE - Office of Energy Efficiency and Renewable Energy (EE)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1038795
• Journal Information: Catalysis Today, Journal Name: Catalysis Today Journal Issue: 1 Vol. 184; ISSN 0920-5861; ISSN CATTEA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CATALYSTS
DISTRIBUTION
NITRATES
OXIDATION
OXYGEN
PERFORMANCE
POISONING
SLIP
STORAGE
SULFATION
SULFUR