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With the ever-increasing stringency of emissions regulations, automotive three-way catalysts (TWCs) require much faster light-off performance and higher warmed-up activity than before. Most automotive manufacturers are considering the adoption of close-coupled catalyst systems as a means of dealing with cold start emissions and need the catalyst to have improved thermal durability. It is still generally true that Pd-based catalyst is suitable for close-coupled application. In this paper, an advanced Pd/Rh is reported to be improved for both cold start and hot emissions. Pd based catalyst has been an excellent catalyst for removing THC and CO at light-off but is weak in NOx. In order to elevate the NOx activity of Pd-based catalyst, Rh has been combined into the catalyst system. The Pd-Rh, Pd-OSC and Rh-OSC interactions were found to be important for the improvement of light-off and warmed-up activities on Pd/Rh catalyst.

With the ever-increasing stringency of emissions regulations, automotive three-way catalysts (TWCs) require much faster light-off performance and higher warmed-up activity than before. Most automotive manufacturers are considering the adoption of close-coupled catalyst systems as a means of dealing with cold start emissions and need the catalyst to have improved thermal durability. In this paper, a new Pd/Rh is reported to be suitable for high temperature application. Due to the recent increasing Pd metal cost, a Pt/Rh with equivalent or better TWC performance needs be developed to balance the PGM usage. A current Pt/Rh catalyst seems to possess comparable TWC performance to the new Pd/Rh catalyst when the catalysts are aged at 900°C. However, aging at a temperature higher than 900°C significantly deactivated the activity of the Pt/Rh catalyst to a point that is much worse than the Pd/Rh catalyst.

The increasing severity in emission standards around the world has been accompanied by the development of more active, durable catalysts. With a view to investigating the effects of high thermal aging on the catalyst performance and structure, the relationships of washcoat composition, washcoat structure, and PGM location with respect to catalyst activity were clarified using a model gas test, as well as physical and chemical characterization methods. The influence of newly developed washcoat components and PGM location on catalyst performance are also demonstrated by engine bench tests. The results obtained in this study indicate the newly developed Pt/Rh catalyst techologies are appropriate for future applications in which the catalyst will be exposed to extremely high temperature and flowrates.

This work investigated the characteristics of both total and methane hydrocarbon emissions from a spark-ignition research engine fuelled with natural gas and gasoline. The engine was operated at a range of equivalence ratios, spark timings and speeds. Measurements were also made during warm-up. The effects of exhaust gas recirculation at stoichiometric operation with special regard to oxides of nitrogen emissions were also investigated in a direct comparison between natural gas and gasoline fuelling at constant engine torque.