Platinum versus Palladium Three-way Catalysts - Effect of Closed-Loop Feedback Parameters on Catalyst Efficiency

Precious metal catalysts have been proven to be the most durable for reduction of automotive exhaust emissions. Currently, three-way catalysts are composed of mainly platinum and rhodium for reduction of CO, NOx and HC. Future catalysts are projected to contain increasing amounts of Pd to reduce current pricing of automotive catalysts. Mnolithic three-way catalysts containing Pt/Rh and Pd/Rh were aged on an engine dynamometer and were subsequently evaluated using engine sweep tests at various perturbation conditions of A/F ratio, amplitude and frequency. Stoichiometric light-off tests were also performed at various perturbation conditions. In addition, these catalysts were evaluated on FTP slave vehicles having widely different control strategies resulting in a substantial range of perturbation conditions.