Study on New Characteristic CeO
Based Material for Advanced TWC
Performance improvements resulting from the adoption of a new type CeO2-ZrO2-based material were found using a two-brick three way catalyst (TWC) system. Compared to a conventional CeO2-ZrO2-based material, this new type CeO2-ZrO2 has both a larger oxygen storage capacity and a slower oxygen release rate. Such characteristics were confirmed by fundamental studies. Vehicle evaluations showed this material was most effective for hot NOx control when used in the rear catalyst, especially after fuel cuts. The improvement in NOx was thought to be caused by the increased oxygen storage capacity (OSC), which effectively stored excess oxygen during fuel cuts. As a result, the air-to-fuel ratio (A/F) surrounding the active sites could be kept at stoichiometry even if the engine control shifted to a lean setting.