Browse Publications Technical Papers 2015-01-1000
2015-04-14

Thermal and Chemical Deactivation of Three-Way Catalysts: Comparison of Road-, Fuel-Cut and SAI- Aged Catalysts 2015-01-1000

The objective of this study was to investigate which of the artificial aging cycles available in the automotive industry that causes major deactivation of three-way catalysts (TWCs) and can be used to obtain an aged catalyst similar to the road aged converter (160 000km).
Standard bench cycle (SBC) aging with secondary air injection (SAI) covered aging with various mass flows - a flow from three cylinders into one catalyst system and a flow from three cylinders into two parallel connected catalysts. For rapid catalyst bench aging, secondary air injection is a very efficient tool to create exotherms. Furthermore, the effect on catalytic activity of SAI aging with poisons from oil and fuel dopants (P, Ca, Zn) was investigated.
The catalysts were thoroughly characterized in light-off and oxygen storage capacity measurements, emission conversion as a function of lambda and load variation was determined. These catalysts were then compared to three-way catalysts aged on an engine bench comparing two fuel-cut (FC) strategies, i.e. fuel-cut retardation (FCR) and fuel-cut acceleration (FCA) [1].
For 40-hour aged samples, SAI aged had the highest total deactivation of the catalytic system. The fuel-cut aging also showed significant deactivation but not to the same extent as the SAI aging cycle. This result can be explained by the different pattern of exotherms and the magnitude of the temperature excursions. The total temperature rise in fuel-cut aging cycles was lower than for SAI aged and which resulted in less sintering of the catalytic washcoat. For the fuel-cut ageing systems the exotherms were growing with the ageing time. This was verified by resulting light-off and oxygen storage capacity (OSC) results.

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