What Really Matters In Three Way Catalyst Light-off?
Andrew (Bean) Getsoian, Ford Motor Company
It is well-known that a large fraction of the cumulative tailpipe emissions from gasoline-powered vehicles are generated during the cold start period before emission control catalysts warm up enough to become active. In order to tackle cold start emissions, the USCar Advanced Combustion and Emission Control Tech Team issued the “150°C Challenge” to encourage development of catalysts with lower light-off temperatures. The premise of much ensuing work has been that if catalysts could become active at lower temperatures, then control of emissions would be achieved earlier in the cold start period and total emissions would be decreased. This has led to a focus in the aftertreatment community on improving reaction kinetics on model catalysts. By contrast, the critical roles of oxygen storage activation, thermal mass, and thermal conductivity have not received the same attention. In the present work, we use modeling tools to demonstrate that even dramatic improvement to reaction kinetics during light-off can have only limited real-world benefit, and that thermal management, oxygen storage activation, and phosphorus poisoning play dominant roles in determining catalyst performance during light-off. This work issues a new challenge to the community to refocus research on catalyst light-off improvement to include consideration of oxygen storage activation, thermal mass, and resistance to poisons.