Development of Advanced Zone-Coated Three-Way Catalysts

In recent years the regulations governing emissions from automobiles have been strengthened as awareness of global environmental problems has increased. Furthermore, the amount of precious metals being used has continued to decrease due to concerns over the exhaustion of natural resources and worries about the risk of fluctuations in the price of these precious metals. As a result, a high performance three-way catalyst that can satisfy the emissions regulations is now required.

By applying zone-coating and carrier degradation control technology, a high performance three-way catalyst has been developed. The zone-coating technology improves the conversion performance of the catalyst through improvement of HC and NO_x conversion reactions and oxygen storage capacity (OSC) reactions. The addition of an Nd surface-enriched layer strengthened the mutual interactions between the carrier and Rh. Moreover, the introduction of an alumina diffusion barrier suppresses ZrO₂ sintering which in turn suppresses Rh grain growth. The new three-way catalyst has adopted these technologies and substantially less Rh is needed compared to conventional catalysts. In addition, this new catalyst is scheduled to be adopted into vehicles starting 2011.