Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Knowledge of the physical and chemical causes of deactivation of TWC

The following have been identified as the main causes of the deactivation:
- Sintering of the cerium oxide containing phases
- Loss of noble metals
- Sintering of the noble metals
- Loss of oxygen storage capacity
- Accumulation of poison (phosphate, lead, calcium, zinc, iron, etc..)

The microactivity test of different used catalysts showed that elimination of NO and hydrocarbons are seriously impaired in used catalyst and the extent to which this occurs is greater in the front section of the monoliths although the rear section of the monoliths are also deactivated but to a lesser extent. Although CO oxidation performance is diminished as a function of catalysts age, it is not affected to the same extent as the NO reduction and hydrocarbon oxidation reactions.

The consequence of these finding will impact on the future design of 3 way catalysts: the result show which of the active sites are most affected by the different causes of deactivation (contaminants or poison accumulation, loss and deterioration of the different active sites of the washcoat, etc). This knowledge should contribute to a better design of the TWC by catalysts manufacturers to increase and to guarantee longer periods of operation.

The barriers for future use of this result will came from the development of new clean fuels for cars. For instance the use of the H2 fuel cell will not require such a catalyst for the elimination of toxic exhaust pipe emissions.

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Reported by

Campus de Cantoblanco
28049 Madrid
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