NOx Storage and Release Activity on Pd/BEA Passive NOx Adsorber
Vu, Anh Viet
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Increasingly stringent vehicular emission regulation on NOx demands a better strategy to further mitigate tailpipe NOx exhaust. In terms of NOx reduction strategy, both current state-of-the-art technologies, selective catalytic reduction (SCR) and NOx storage and reduction (NSR), have shown optimal performance in warm conditions but are not fully functional at temperature below 200°C, commonly regarded cold-start condition. Thus, in order to mitigate NOx cold-start emission, the passive NOx adsorber (PNA) has been introduced. Among the potential PNAs, Pd/BEA stands out due to its promising NOx storage capacity and well-controlled thermal desorption performance. In this Masters thesis, NOx adsorption and desorption on Pd/BEA was studied using temperature-programmed desorption method. It was shown that CO improved NOx storage and induced NOx release to higher temperature on Pd/BEA where the chemical state of Pd is key. The desorption kinetics of NOx on Pd/BEA was also studied in an attempt to resolve the effect of heating rate on the controlled release of NOx.