Development of Three-Way Catalyst with Advanced Coating Layer

Further improvements in catalyst performance are required to help protect the atmospheric environment. However, from the viewpoint of resource availability, it is also necessary to decrease the amount of precious metals used at the active sites of the catalyst. Therefore, a high-performance three-way catalyst with an advanced coating layer has been developed to lower the amount of precious metal usage. Fuel efficiency improvement technologies such as high compression ratios and a large-volume exhaust gas recirculation (EGR) generally tend to increase the ratio of hydrocarbons (HC) to nitrogen oxides (NOx) in exhaust gas. This research focused on the palladium (Pd) loading depth in the coating layer with the aim of improving the hydrocarbon (HC) conversion activity of the catalyst. Contact between Pd, which has a high degree of HC conversion activity, and the exhaust gas can be facilitated by controlling the loading depth on the surface of the coating layer, enabling efficient conversion even under high space velocity (SV) conditions. Subsequently, this research focused on the coating structure to maximize the conversion activity and oxygen storage capacity (OSC) performance and improve gas diffusivity in the coating layer. The particle size of each coating material was controlled to maximize the heat resistance and OSC performance. The coating thickness was controlled by applying finer alumina and fabricating connected pores. This coating structure ensures excellent gas diffusivity without affecting the pressure drop. As a result, the developed catalyst achieves high conversion activity with nearly 20% less precious metal usage. This catalyst will start to be introduced in vehicles from 2020.