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DPF SCR ASC Urea injection DRIFTs and bench-scaled reactor Experiments CO Effects on Pd-BEA and Pd-ZSM-5 as Model Catalysts for Passive NOx Adsorption Yuntao Gu 1 , Sreshtha Sinha Majumdar 2 , Josh A. Pihl 2 , Todd J. Toops 2 and William S. Epling 1 1 University of Virginia, 2 Oak Ridge National Laboratory In - situ DRIFTs Study & Proposed PNA Mechanism − − − 1838 cm -1 − − 2 − +2NO 1818 cm -1 @T<100°C NO 2 +CO,NO − 1818 cm -1 CO 2 , CO and NO 2130 1873 1838 1640 1583 1873 1838 1873 1838 1818 1818 1873 1838 1818 1818 1873 1838 1873 cm -1 • 2130: [ − ] − • 1640: 2 + − − • 1583: + − − • 1873: − − • 1838: − • 1818: − & − − [()] − +2 2 → − +[ 2 − ] − 2 − → 2 − () + + 2 + 2 2 − → 2 − +2 + 2 + 2 + DRIFTs Peak Assignment Dominating Surface Reaction Temperature Programmed Desorption • Simultaneous release of NO and CO starting from 175°C confirms the existence of: − , the step change of the CO oxidation activity at 175°C indicates a different Pd n+ site distribution caused by the proposed surface reaction: • O 2 concentration affects Pd n+ site distribution leading to different CO light-off behaviors and NOx desorption profiles, while NOx storage capacity is not affected. 2 − → 2 − +2 + 2 + 2 + Motivation: Cold Start Emission Control PNA+DOC NOx CO PM HC CO 2 H 2 O N 2 PNA Adsorption Chemistry Acknowledgement The authors gratefully acknowledge support from the Department of Energy, Vehicle Technologies Office (DE-EE0008233) This research was supported in part by an appointment to the Oak Ridge National Laboratory ASTRO Program, sponsored by the U.S. Department of Energy and administered by the Oak Ridge Institute for Science and Education Comparison between Pd - ZSM - 5 and Pd - BEA Fresh CO Exposed H 2 Reduced Re-Oxidized • NOx TPD profiles of both Pd-BEA and Pd-ZSM-5 consists of two desorption features. • Similar short-term CO effects on desorption characteristics are observed • Pd-BEA seems to suffer an irreversible loss of NOx storage capacity caused by CO exposure, while the NOx storage capacity of Pd-ZSM-5 is relatively consistent. • Transient CO release happens only on Pd-ZSM-5 Similarity and difference NO (ppm) CO (ppm) 1 4 7 10 × 13 O 2 (%): 175 °C 0 5 7 9 × 11 CO 2 (%): + 13 NO (ppm) CO (ppm) 75 100 125 150 × 175 T (°C): + 200 − 225 NO (ppm) CO (ppm) Experimental Methodology • Pd loading: 50 g/ft 3 (1.8 g/l) • Washcoated on a 400 cells/in 2 cordierite monolith • Loaded in automated synthetic exhaust flow reactor • Degreened at 600 °C for 4 h under 10% O 2 , 7% H 2 O and N 2 Pd-exchanged ZSM-5 MultiGas TM 2030 PrismaPlus TM TPD @ 20 °C/min CO on NO on NO off Picture from Thermo Scientific Hydrothermal aging conditions O 2 10% H 2 O 7% T 600°C SV 30000 h -1 Pretreat, cool conditions O 2 10% H 2 O 0% T 550°C NO exposure conditions NO 200 ppm CO 200 ppm (0 or 200) O 2 10% H 2 O 4.5% (0-4.5%) CO 2 0% T 100°C US DoE DEER Conference 2011 - Cary Henry, Hai-Ying Chen et. Al CO NH 22 +H 2 O → CO 2 +2NH 3 C n H m + （n+ 2 ）O 2 → nCO 2 + 2 H 2 O CO + 1 2 O 2 → CO 2 O 2 + 4NO + 4NH 3 → 6H 2 O +4N 2 Selective Catalytic Reduction Ammonia Oxidation 3 2 O 2 + 2NH 3 → 3H 2 O +N 2 NOx Release NO ∗ → NO x +∗ NO + ∗→ NO ∗
