Synergistic Effect of Cu/CeO2 and Pt-BaO/CeO2 Catalysts for a Low-Temperature Lean NOx Trap

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A lean NOx trap (LNT) catalyst has been widely used for removing NOx exhaust from lean-burn engines. However, the operation range of LNT has been limited because of the poor activity of LNT catalysts at low temperatures (<= 300 degrees C), especially in urban driving conditions. To increase NOx removal efficiency during lean rich cycle operation, a Cu/CeO2 (CC) catalyst was added to a Pt-BaO/CeO2 (PBC) catalyst. In comparison to PBC- or CC-only catalysts, the physical mixture of PBC and CC catalysts (PBC + CC) exhibited a significant synergy for both NO, storage and reduction efficiencies. In particular, low-temperature activity below 200 degrees C was greatly enhanced. A Pt-BaO-Cu/CeO2 (PBCC) catalyst, which was synthesized by depositing Pt and Cu together on a ceria support, showed poorer NOx removal efficiency. The origin of the synergistic effect over PBC + CC was investigated. Under lean conditions, the CC showed much better activity for NO oxidation, allowing for faster NOx storage on PBC. Under rich conditions, H-2 was generated in situ on the CC by a water-gas shift reaction then accelerated the reduction of NOR, which had been stored on PBC, with a higher selectivity to N-2. This simple modification in the catalyst can provide an important clue to enhance low-temperature activity of the commercial LNT system.
Publisher
AMER CHEMICAL SOC
Issue Date
2019-03
Language
English
Article Type
Article
Citation

ENVIRONMENTAL SCIENCE &amp; TECHNOLOGY, v.53, no.5, pp.2900 - 2907

ISSN
0013-936X
DOI
10.1021/acs.est.8b05329
URI
http://hdl.handle.net/10203/254112
Appears in Collection
CBE-Journal Papers(저널논문)
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