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Durability Testing of Stabilized Ru-Containing Catalysts
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Abstract
Ruthenium-containing catalysts have good activity and selectivity for the reduction of the nitric oxides in automobile exhaust. Although designed to be operated under reducing conditions, these catalysts lose Ru by volatilization when subjected to lean transients. Attempts were made to stabilize these catalysts against volatilization by forming stable ruthenates. This paper deals with durability testing of stabilized ruthenate catalysts on a laboratory bench set-up, dynamometers, and vehicles. Post-mortem analysis of the durability-tested catalysts are presented showing the extent of stabilization. The results show that the Ru loss from ruthenate catalysts in present vehicle systems is in excess of acceptable limits. These losses can be minimized further, but at a cost of reduced selectivity in the NO reduction. Substantial further improvements are needed to achieve the required performance characteristics.
Another problem is the poisoning by S, Pb and P. The catalysts have been analyzed to determine the various poisons deposited by the engine exhaust. The retention of Pb, S, and P by catalysts from exhaust was determined in well-controlled dynamometer tests. The BET area and active metal area were measured before and after the tests to determine the extent of thermal sintering. Actual temperature traces of catalysts under customer-type driving have shown temperature excursions up to 1900°F.
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Gandhi, H., Stepien, H., and Shelef, M., "Durability Testing of Stabilized Ru-Containing Catalysts," SAE Technical Paper 750177, 1975, https://doi.org/10.4271/750177.Also In
References
- Meguerian G. H. Lang C. R. “NO x Reduction Catalysts for Vehicle Emission Control.” SAE Transactions 80 1971 paper 710291
- Shelef M. Gandhi H. S. “Ammonia Formation in Catalytic Reduction of Nitric Oxide by Molecular Hydrogen. I. Base Metal Oxide Catalysts.” Ind. & Eng. Chemistry, Prod. Res. & Dev. 11 1972
- Klimisch R. L. Barnes G. J. “Chemistry of Catalytic Nitrogen Oxide Reduction in Automobile Exhaust Gas.” Environmental Science & Technology 6 1972
- Shelef M. Gandhi H. S. “Ammonia Formation in Catalytic Reduction of Nitric Oxide. III. The Role of Water Gas Shift, Reduction by Hydrocarbons and Steam Reforming.” Ind. & Eng. Chemistry., Prod. Res. & Dev. 13 1974
- Shelef M. Gandhi H. S. “Ammonia Formation in Catalytic Reduction of Nitric Oxide by Molecular Hydrogen. II. Noble Metal Catalysts.” Ind. & Eng. Chemistry, Prod. Res. & Dev. 11 1972
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- Shelef M. Gandhi H. S. “The Reduction of NO in Automobile Emissions. Stabilization of Catalysts Containing Ru.” Platinum Metals Review 18 January 1974
- Kobylinski T. P. Taylor B. W. “Stabilized Ru Catalysts for NO x Reduction.” Paper 740250 SAE Automotive Engineering Congress Detroit February 1974
- Gandhi H. S. “Discussion of SAE Paper 740250 ” SAE transaction
- Gibbons E. F. Meitzler A. H. Foote L. R. Zacmanidis P. J. Beaudoin G. L. “Automotive Exhaust Sensors Uning Titania Ceramics.” Paper 750224 SAE Automotive Engineering Congress Detroit February 1975