This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Physico-Chemical and Catalytic Properties of CeO2-ZrO2 Solid Solutions Supported and Dispersed on γ-Al2O3
Annotation ability available
Sector:
Language:
English
Abstract
Three-way conversion (TWC) catalyst supports were prepared having CeO2-ZrO2 solid solution particles uniformly dispersed on γ-Al2O3 as discrete crystallites. The support morphology was characterized using STEM and TEM analysis. TPR and XRD analyses were also carried out on precious metal (PM) containing and PM-free samples before and after aging. These studies were combined with performance measurements which demonstrated the beneficial effects of solid solution formation on TWC catalyst activity.
STEM and TEM analysis showed that well-dispersed CeO2-ZrO2 solid solution particles could be formed and simultaneously supported on a high surface area γ-Al2O3 support. For samples calcined up to 600°C, crystallite sizes of ≤50Å were formed as compared to sizes of over 200Å in the aged samples. The TPR studies suggested that for supports calcined up to 600°C most of the CeO2 present was reduced from the Ce4+ to the Ce3+ state in the temperature range 250 - 700°C. H2 uptake in this temperature range was assigned to reduction of Ce4+ ions at the surface or sub-surface of CeO2 crystallites. The addition of Pt and Rh to the supports resulted in a synergistic reduction of the PMs and CeO2, again with most of the CeO2 undergoing reduction, especially for solid solution containing samples. After aging, it was further shown that CeO2-ZrO2 solid solution formation clearly promoted CeO2 reduction at temperatures typically associated with surface CeO2 reduction. Thus, the CeO2-ZrO2 supported and dispersed solid solutions showed the same enhancements in redox activity as observed earlier for non-supported materials. XRD analysis was used to confirm that solid solution formation occurred for the Zr-containing samples and to give a qualitative measure of the CeO2 crystallite size.
Performance measurements were carried out on Zr-free and Zr-containing air aged samples that were washcoated onto monolith substrates. For these catalysts, it was shown that performance advantages were observed for the Zr-containing samples after laboratory aging at 1000°C for 24 hours in air. Characterization of the aged samples using a combination of XRD and TEM further confirmed that the morphology consisted of evenly dispersed CeO2-ZrO2 solid solution cryslallites on the Al2O3 surface. Similar CeO2 crystallite size trends were found for the XRD and TEM analysis, and it was found that doping with Zr stabilized the CeO2 with respect to sintering.
Recommended Content
Technical Paper | The Role of Zirconium in Novel Three-Way Catalysts |
Journal Article | Applicable Diesel Oxidation Catalyst for Multi-Diesel Exhaust System |
Technical Paper | Effect of Ba and La Additives to the Pd Layer of a Pd:Rh TWC |
Authors
Citation
Nunan, J., "Physico-Chemical and Catalytic Properties of CeO2-ZrO2 Solid Solutions Supported and Dispersed on γ-Al2O3," SAE Technical Paper 970467, 1997, https://doi.org/10.4271/970467.Also In
References
- Harrison B. Diwell A. F. Hallett C. Platinum Metal. Rev. 32 73 1988
- Sergeys F. J. Masellei J. M. Ernest M. V. W. R. Grace Co. 1974 Hindin S. G. Engelhard Mineral and Chemical Co. 1973
- Gandhi H. S. Piken A. G. Shelef M. Delosh R. G. “Laboratory Evaluation of Three-Way-Catalysts” SAE Paper No. 760201 1976
- Su E. C. Montreuil C. N. Rothchild W. G. “Oxygen Storage Capacity of Three-Way Catalysts” Appl. Catal. 17 75 1985
- Yao Y. F. Yu “Oxidation of CO and Hydrocarbons over Noble Metal Catalysts” J. Catal. 87 152 1984
- Oh S. H. Eickel C. C. J. Catal. 112 543 1988
- Sass A. S. Shvets V. A. Savel'era G. A. Povova N. M. Kazanskii V. B. Kinet. Katal. 27 894 1986
- Nunan J. G. Cohn M. J. Donner J. T. “Effect of High Temperature Aging on the Performance of Pt,Rh/CeO 2 and Rare earth/Alkaline Earth Doped Pt,Rh/CeO2 Catalysts” Catalysis Today 14 277 1992
- Matsumoto S. Sato M. Shinjoh H. 1989 Toyota Central Research and Development Toyota Jidosha KK Matsumoto S. Miyoshi N. Kimura M. Ozawa M. Isogai A. 1990 Toyota Chuo Kenkyusho Toyota Jidosha KK Kimura M. Matsumoto S. Ozawa M. Sobukawa H. Tanaka H. Tsuboi H. 1993 Daihatsu Motor Co. Ltd. Toyota Chuo Kenkyusho Toyota Central Research and Development Lab Toyota Jidosha KK
- Murota T. Hagesawa T. Aozasa S. Matsui H. Motoyama M. Alloys and Compounds 193 298 1993
- Ozawa M. Kimura M. Isogai A. “The application of Ce-Zr Oxide Solid Solution to Oxygen Storage Promoters in Automotive Catalysis” J. Alloys and Compounds 193 73 1993
- Rao G.Ranga Kaspar J. Meriani S. di Monte R. Graziani M. “NO Decomposition over Partially Reduced Metallized CeO 2 -ZrO 2 Solid Solutions” Catal. Lett. 24 107 1994
- Fornasiero P. Di Monte R. Rao G. Ranga Kaspar J. Meriani S. Trovarelli A. Graziani M. “Rh-loaded CeO 2 -ZrO 2 Solid Solutions as Highly Efficient Oxygen Exchangers: Dependence of the Reduction Behavior and the Oxygen Storage Capacity on the Structural Properties” J. Catal. 151 168 1995
- Rao G. Ranga Fornasiero P. Di Monte R. Kaspar J. Vlaic G. Balducci G. Meriani S. Gubitosa G. Cremona A. Graziani M. “Reduction of NO Over Partially Reduced Metal-Loaded CeO 2 -ZrO 2 Solid Solutions” J.Catal. 62 1 1996
- de Leitenburg C. Trovarelli A. Llorca J. Cavani F. Bini G. “The effect of Doping CeO 2 with Zirconium in the Oxidation of Isobutane” Appl. Catal. A: General 139 161 1996
- Fornasiero P. Balducci G. Kaspar J. Meriani S. Di Monte R. Graziani M. “Metal-Loaded CeO 2 -ZrO 2 Solid Solutions as Innovative Catalysts for Automotive Catalytic Converters” Catal. Today 29 47 1996
- Nunan J. Williamson B. Robota H. “Advanced TWC Technologies Using CeO 2 /ZrO 2 Solid Solutions” SAE Paper 960798 February 26-29 1996
- Miki T. Ogawa T. Haneda M. Kakuta N. Ueno A. Tateishi S. Matsuura S. Sato M. “Enhanced Oxygen Storage Capacity of Cerium Oxides in Cerium Dioxide/Lanthanum Sesquioxide/Alumina Containing Precious Metals” J. Phys. Chem. 94 644 1990
- Nunan J. G. Robota H. J. Cohn M. J. Bradley S. A. “Physicochemical Properties of Ce-Containing Three-Way Catalysts and the Effect of Ce on Catalyst Activity” J. Catal. 133 309 1992
- Nunan J. G. Williamson W. B. Robota H. J. Henk M. G. “Impact of Pt-Rh and Pd-Rh Interactions on Performance Features of Bimetal Catalysts” SAE Paper 950258 1995
- Johnson M. F. L Mooi J. “Cerium Dioxide Crystallite Sizes by Temperature Programmed Reduction” J. Catal. 103 502 1987
- Yao H. C. Yao Y. F. Yu “Ceria in Automotive Exhaust Catalysts, 1. Oxygen Storage” J. Catal 86 254 1984
- Fierro J. Soria J. Sanz J. Rojo J. “Induced Changes in Ceria by Thermal Treatments under Vacuum or Hydrogen” J. Solid State Chem. 66 154 1987
- Bernal S. Calvino J. Cifredo G. Gatica J. Perez J. Omil Pintado J. “Hydrogen Chemisorption on Ceria: Influence of the Oxide Surface Area and Degree of Reduction” J. Chem. Soc., Faraday Trans. 89 3499 1993