Improved three-way catalyst with the ignition layer for reducing cold emissions

Exhaust gas regulations, such as Tier4, Euro7, and China7, are being strengthened. In addition to the regulated values during specified driving patterns, emission is required to be reduced at various usage patterns. Among these, the cold emission account for a significant portion of the total emission and improving catalytic purification performance during cold start is strongly demanded. To address this, we are being needed to use large amounts of precious metals. In this study, we focus on the cold emission and explain the new catalyst which introduces the ignition layer aimed at the effective utilization of Pd. The ignition layer is the new technology that aims to improve cold start performance by arranging Pd, which has high activity at low temperatures, on the front side, upper layer, and in high density. However, there are some concerns such as reduced activity of the Rh layer and increased sulfur impact. As these counter measure, a porous structure is introduced to maintain gas contact with Rh located in the lower layer and maintain NOx purification activity. Additionally, the introduction of Al2O3-CeO2-ZrO2 material which has low-basicity into the Pd support reduces the impact of sulfur. Furthermore, by adapting the Al2O3-CeO2-ZrO2 material with high Pd loading and durability, the function as the ignition layer is maximized. By combining these technologies, the introduction of the ignition layer is made possible, and the developed catalyst shows high performance while reducing the amount of precious metal used by 12% compared to the conventional catalyst. It successfully achieves a high level of both emission suppression and reduction in precious metal usage. This catalyst is scheduled to be gradually installed in vehicles starting from the fall of 2025.