Development of NOx Storage Catalyst and Investigation of Deterioration Mechanism for Small Powertrains

<div class="section abstract"><div class="htmlview paragraph">In response to the evolving landscape of exhaust gas regulations for small powertrains, reducing NOx emission is increasingly important. This study deeply investigated the feasibility of a NOx storage catalyst (NSC) containing cerium oxide (CeO<sub>2</sub>) and barium oxide (BaO) for reducing NOx emission.</div><div class="htmlview paragraph">The key functions, NOx storage and reduction performances were evaluated, and deterioration mechanisms were explored through performance evaluations and physical property analyses. The findings revealed a strong correlation between the size of CeO<sub>2</sub> crystals and NOx storage performance at low temperature, such as those encountered during city driving conditions. Conversely, at high temperature, such as those during highway driving conditions, NOx storage performance correlated well with sulfur deposition, suggesting that the formation of barium sulfate (BaSO<sub>4</sub>) contributes to the deactivation. This experiment also showed a strong correlation between NOx reduction performance and BaSO<sub>4</sub> formation.</div><div class="htmlview paragraph">A new aging method that can simulate both thermal and sulfur deterioration was established based on these findings. This method effectively reflects field aging conditions.</div><div class="htmlview paragraph">A new NSC based on the concept of resisting this newly established aging method showed significantly improved performance in both NOx storage and reduction. Despite an increase in the amount of barium components compared to the conventional NSC, high performance was maintained after sulfur poisoning. In the case of the new NSC, it was found that weakly basic chemical introduced as a sulfur scavenger suppresses the formation of BaSO<sub>4</sub>. This new NSC concept is expected to be leveraged in a wide range of vehicles including small powertrains, to achieve robust performance.</div></div>