Development of Three-way Catalysts with Advanced Coating Layer 2020-01-0653
In order to protect the atmospheric environment, further improvement of catalyst performance is required. On the other hand, from the viewpoint of resource risk, it is necessary to reduce the amount of precious metal used as active sites of the catalyst. Therefore, we have developed a high performance three-way catalyst with advanced coating layer to achieve the reduction of precious metal usage.
In recent years, fuel efficiency improvement technologies such as a high compression ratio and a large amount of Exhaust Gas Recirculation (EGR) have attracted attention. These technologies generally tend to increase the ratio of HC to NOx in exhaust gas. In order to improve the HC purifying activity of the catalyst, we focused on the Pd loading depth in the coating layer. By controlling the loading depth on the surface of the coating layer, Pd with high HC purification activity is easily in contact with exhaust gas. And it became possible to purify efficiently even under high Space Velocity (SV) conditions.
Subsequently, we focused on the coating structure to maximize purifying activity and improve gas diffusivity in the coating layer. The particle size of each coating materials was controlled to maximize heat resistance and oxygen storage capacity (OSC) performance. The coating thickness was controlled by applying finer alumina and making connected pore. This coating structure had excellent gas diffusivity without affecting pressure drop.
As a result, the developed catalyst shows high purifying activity with nearly 20% reduction of precious metal usage. This catalyst started to introduce into vehicle from 2020.