NOx adsorption and desorption of a Mn-incorporated NSR catalyst Pt/Ba/Ce/xMn/γ-Al2O3
2019
Wang, Pan | Yu, Dan | Wu, Gang | Sheikh, Farhan | Liu, Junheng
This study evaluated the NOₓ adsorption and desorption performance as well as the casual relationship underlying a Mn-incorporated catalyst (Pt/Ba/Ce/xMn/γ-Al₂O₃). NOₓ adsorption and desorption are regarded as a prominent index for the NOₓ removal performance of NOₓ storage and reduction; we utilized NOₓ storage experiments with various inlet NO and O₂ concentrations and cycling adsorption/desorption experiments with a couple of adsorption time protocols for performance evaluation. In-suit DRIFT and NOₓ-TPD tests were implemented to reveal the instant stored species and their thermal stability. Eight percent of Mn catalyst at 350 °C was adopted in the described experiments for its desirable NOₓ adsorption characteristics. The optimal NOₓ storage performance was found under 10% O₂, deteriorating when the concentration was further increased. Furthermore, elevating NO concentration impaired the NOₓ adsorption due to the low NO₂/NOₓ ratio. It was also found that shorter adsorption time facilitated NOₓ removal via maintaining an unsaturated state for active storage components in terms of a fixed desorption time. The stored species existed as nitrites and nitrates with a good low-temperature thermal stability which however decayed at higher temperatures as exhibited in the DRIFT and NOₓ-TPD tests. These findings provided invaluable information for the application of Mn-incorporated catalyst for NOₓ removal in diesel exhaust purification to relieve the aerial pollution.
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