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Dual-Catalyst Underfloor LEV/ULEV Strategies for Effective Precious Metal Management
Technical Paper
1999-01-0776
ISSN: 0148-7191, e-ISSN: 2688-3627
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English
Abstract
Dual-brick catalyst systems containing Pd-only catalysts followed by Pt/Rh three-way catalysts (TWCs) provide an effective strategy for managing Pt, Pd and Rh precious metal inventories while achieving LEV/ULEV emission standards. Engine aged dual-brick converters containing front Pd catalysts followed by rear Pd/Rh or Pt/Rh TWCs demonstrated LEV emission levels in an underfloor location on a TLEV calibrated 3.8L vehicle, and achieved ULEV emissions with air addition. Using identical advanced washcoat formulations stabilized with ceria-zirconia promoters, single-brick Pt/Rh TWCs demonstrated equivalent performance to Pd/Rh TWCs after thermally severe aging, and dual-brick [Pd + Pt/Rh] systems also had equivalent performance to [Pd + Pd/Rh] catalyst systems. While a Pd-only system also achieved 100K mi equivalent LEV emissions, both dual-brick options lowered emissions further using substantially lower loadings and more balanced precious metal usage.
The front Pd-only catalyst effectively controls HC emissions with loading dependent on converter inlet temperatures, but can be formulated to also help control NOx emissions. Cerium-free Pd formulations demonstrated 50°C lower aged light-off temperatures than Pd TWCs during modulated, non-modulated, and lean light-off conditions that were confirmed in vehicle testing. Higher Pd loadings may require catalyst washcoat optimizations, as aged catalyst light-off improved with increased Pd dispersion. Additional HC rapid temperature ramp light-off benefits and vehicle HC performance are demonstrated with higher cell density and thinner-wall substrates. When the front Pd catalyst formulation also contained stabilized ceria-zirconia promoters, NOx control of the dual-brick systems was further improved.
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Williamson, W., Dou, D., and Robota, H., "Dual-Catalyst Underfloor LEV/ULEV Strategies for Effective Precious Metal Management," SAE Technical Paper 1999-01-0776, 1999, https://doi.org/10.4271/1999-01-0776.Also In
References
- Kishi, N. Kikuchi S. Seki Y. Kato A. Fujimori K. “Development of the High Performance L4 Engine ULEV System” SAE Paper 980415 1998
- Summers, J.C. Skowron J.F. Miller M.J. “Use of Light-Off Catalysts to Meet the California LEV/ULEV Standards” SAE Paper 930386 1993
- Williamson, W.B. Denison G.W. Starin G.L. Robota H.J. “Palladium-Rhodium Catalyst Strategies for LEV Emission Applications” SAE Paper 972844 1997
- Smaling, R.M. Sung S. Bartlett R. “Washcoat Technology and Precious Metal Loading Study Targeting the California LEV MDV2 Standard” SAE Paper 961904 1996
- Otto, E. Albrecht F. Liebl J. “The Development of BMW Catalyst Concepts for LEV/ULEV and EU III/IV Legislations - 6 Cylinder Engine with Close Coupled Main Catalyst” SAE Paper 980418 1998
- Hu, Z. Heck R. M. “High Temperature Ultra Stable Close Coupled Catalysts” SAE Paper 950254 1995
- Brisley, R.J. Chandler G.R. Jones H.R. Anderson P.J. Shady P.J. “The Use of Pd in Advanced Catalysts” SAE Paper 950259 1995
- Chen, S-L.F. Amundsen A.R. Rabinowitz H.N. Yamada T. “The Development of a Close Coupled Plus Underfloor Catalyst for a ULEV Application” SAE Paper 960796 1996
- Ball, D.J. “Distribution of Warm-Up and Underfloor Catalyst Volumes” SAE Paper 922338 1992
- Ball, D.J. “A Warm-up and Underfloor Converter Parametric Study” SAE Paper 932765 1993
- Summers, J.C. White J.J. Williamson W.B. “Durability of Palladium Only Three-Way Automotive Emission Control Catalysts” SAE Paper 890794 1989
- Muraki, H. “Performance of Palladium Automotive Catalysts” SAE Paper 910842 1991
- Harkonen, M. Kivioja M. Lappi P. Mannila P. Maunula T. Slotte T. “Performance and Durability of Palladium Only Metallic Three-Way Catalyst” SAE Paper 940935 1994
- Ball, D.J. “A Warm-Up - Underfloor Converter Parametric Study: Effects of Catalyst Technology on Emission Performance” SAE Paper 961905 1996
- Yamamoto, M. Tanaka H. “Influence of Support Materials on Durability of Palladium in Three-Way Catalyst” SAE Paper 980664 1998
- Sims, G.S. Johri S. “Catalyst Performance Study Using Taguchi Methods” SAE Paper 881589 1988
- Ball, D.J. Mohammed A.G. Schmidt W.A. “Application of Accelerated Rapid Aging Test (RAT) Schedules with poisons: The Effects of Oil Derived Poisons, Thermal Degradation and Catalyst Volume on FTP Emissions” SAE Paper 972846 1997
- Tamura, N. Matsumoto S. Kawabata M. Kojima M. Machida M. “Development of an Automotive Catalyst using a Thin Wall (4 mil/400cpsi) Substrate” SAE Paper 960557 1996
- Machida, M. Yamada T. Makino M. “Study of Ceramic Catalyst Optimization for Emission Purification Efficiency” SAE Paper 940784 1994
- Day, J.P. Socha, L.S. Jr. “The Design of Automotive Catalyst Supports for Improved Pressure Drop and Conversion Efficiency” SAE Paper 910371 1991
- Socha, L.S. Jr., Day J.P. Barnett E.H. “Impact of Catalyst Support Design Parameters on FTP Emissions” SAE Paper 892041 1989
- Blanchet, S. Richmond R. Vaneman G. “Implementation of the Effectivenss-Ntu Methodology for Catalyst Converter Design” SAE Paper 980673 1998