Browse Publications Technical Papers 2010-01-0364

Investigation on NOx Storage Characteristics and Aging Influence of Lean NOx Trap Model Catalyst BaO-Pt/Al2O3 2010-01-0364

Barium oxide (BaO) and platinum (Pt) are the key components in lean NOx trap (LNT) catalysts. Previous work has demonstrated that highly dispersed and bulk-like BaO species have low-temperature (LT) and high-temperature (HT) release features for stored nitrogen dioxide (NO₂). To better understand the roles of both BaO and Pt, a series of BaO/Al₂O₃ and BaO-Pt/Al₂O₃ were prepared and used to investigate the release characteristics of stored NO₂. Two typical BaO-Pt/Al₂O₃ catalysts having 75% and 44% of dispersed BaO, respectively, were aged and used for both the static NO₂ storage and the dynamic NOx elimination by lean-rich cyclic reactions. Results showed that bulk-like BaO plays a lesser role in storing NO₂ than does dispersed BaO. Pt inhibits the formation of nitrates and thus decreases NO₂ storage capacity (NSC) as Pt can catalyze the release, particularly for NO₂ species stored on bulk-like BaO. Aging in the range of 750-950°C resulted in a decrease of NSC but the HT release peak was restored with release features similar to those for NO₂ stored on BaO/Al₂O₃, indicating that the Pt inhibiting role weakens on the formation of nitrate over aged BaO-Pt/Al₂O₃. Lean-rich cyclic reactions have shown that the BaO-Pt/Al₂O₃ catalyst that was aged at 950°C totally lost the ability to eliminate NOx in the range of 250-600°C in the lean cycles due to Pt sintering. These Pt crystallites were still able to catalyze the lean cycle's oxidation of NO to NO₂ and the rich cycle's reduction of NO, suggesting that the sintered Pt particles significantly decreased the spillover ability of NOx from Pt to BaO species.


Subscribers can view annotate, and download all of SAE's content. Learn More »


Members save up to 43% off list price.
Login to see discount.
Special Offer: With TechSelect, you decide what SAE Technical Papers you need, when you need them, and how much you want to pay.