Effect of Ceria on the Storage and Regeneration Behavior of a Model Lean NO x Trap Catalyst

Ji, Yaying; Toops, Todd J.; Crocker, Mark

doi:10.1007/s10562-007-9226-2

Cited by 67 publications

(33 citation statements)

References 16 publications

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“…This makes ceria-containing catalysts particularly attractive for relatively low temperature applications, given that BaObased formulations typically perform poorly at temperatures below 250ºC [9]. The presence of ceria has also been shown by some workers to be beneficial for the NOx reduction function of NSR catalysts [5,6,8,11,12], and for increasing the selectivity of NO x reduction to N2 (rather than NH3) [11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%

“…Ceria can act as a support material and is particularly effective at stabilizing high Pt dispersions [3], in addition to BaO [4]. Moreover, ceria is able to store NOx at low to moderate temperatures [5][6][7][8][9][10], thereby improving NSR NOx storage capacity. This makes ceria-containing catalysts particularly attractive for relatively low temperature applications, given that BaObased formulations typically perform poorly at temperatures below 250ºC [9].…”

Section: Introductionmentioning

confidence: 99%

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Pt/Ce Pr1−O2 (x= 1 or 0.9) NO storage–reduction (NSR) catalysts

Rico-Pérez

Bueno‐López

Kim

et al. 2015

Applied Catalysis B: Environmental

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Model Pt/Ce0.9Pr0.1O2 and Pt/CeO2 NOx storage-reduction catalysts were prepared via nitrate calcination, co-precipitation and carbon-templating routes.Raman spectroscopic data obtained on the catalysts indicated that the introduction of praseodymium into the ceria lattice increased the concentration of defect sites (vacancies), arising from the higher reducibility of the Pr 4+ cation compared to Ce 4+ . For the Pr-promoted samples, H2-TPR profiles contained high temperature bulk reduction peaks which were less pronounced compared with their ceria analogs, indicating that the presence of praseodymium enhances oxygen mobility due to the creation of lattice defects. Under lean-rich cycling conditions, the cycle-averaged NOx conversion of the Pt/Ce0.9Pr0.1O2samples was in each case substantially higher than that of the Pt/CeO2 analog, amounting to a difference of 10-15% in the absolute NOx conversion in some cases. According to DRIFTS data, a double role can be assigned to Pr doping; on the one hand, Pr accelerates the oxidation of adsorbed NOx species during the lean periods. On the other hand, Pr doping destabilizes the adsorbed NOx species during the rich periods, and the kinetics of nitrate decomposition are faster on Pt/Ce0.9Pr0.1O2, leading to improved catalyst regeneration. These results suggest that ceria-based mixed oxides incorporating Pr are promising materials for NOx storage-reduction catalysts intended for low temperature operation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Pt/Ce Pr1−O2 (x= 1 or 0.9) NO storage–reduction (NSR) catalysts

Rico-Pérez

Bueno‐López

Kim

et al. 2015

Applied Catalysis B: Environmental

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“…However, most of the previous studies focused on the structure characterization or NO x storage capacity testing of the catalyst [12][13][14][15][16][17][18][19], without considering both lean and rich stages of NSR process. As more emphasis has been paid on the reduction process of typical NSR catalyst, we tried to give a realistic evaluation of catalytic behavior for ceria supported catalysts by using different reductants.…”

Section: Introductionmentioning

confidence: 99%

Effects of temperature and reductant type on the process of NOx storage reduction over Pt/Ba/CeO2 catalysts

Wang

2011

Applied Catalysis B: Environmental

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a b s t r a c tThe influences of temperature and reductant type on NO x storage and reduction behavior were studied by transient lean/rich cycles and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments over Pt/Ba/CeO 2 catalysts. It is found that the reducing ability of H 2 is more predominant than that of CO and C 3 H 6 especially at low temperatures. DRIFTS results showed that NO x can be stored as nitrates on both Ba and Ce sites by replacing carbonates species during the lean phase. During the rich phase, however, H 2 regenerated Ba storage sites more effectively than did CO and C 3 H 6 , and Ba(NO 3 ) 2 could be easier reduced than Ce(NO 3 ) 4 . The relatively low reduction performance of CO was attributed to Pt sites being poisoned by CO, which affected low temperature performance, and by carbonates formation, which affected high temperature conversions. The least reactivity of C 3 H 6 was due to its lowest activation ability by the catalysts. Furthermore, water addition had a positive effect on CO reduction ability at 200• C but little influence at elevated temperatures. It was assumed that H 2 O improved the low temperature NO x reduction process by alleviating CO poisoning of Pt.

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“…The alkali or alkaline earth acts as the NO X storage component, forming the nitrite or nitrate species. Other components may be added, including oxygen-storage capacity components (OSC) and other precious metals for the redox steps [9][10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Spatially-Resolved Calorimetry: Using IR Thermography to Measure Temperature and Trapped NOX Distributions on a NOX Adsorber Catalyst

et al. 2008

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Spatial-and time-resolved temperature distributions over a Pt/Ba/Al 2 O 3 model NO X storage/reduction (NSR) catalyst were measured using infra-red thermography. The heat generated during regeneration was correlated to surface nitrate reduction, thereby revealing the concentration of surface nitrates at specific locations along the catalyst. The results demonstrate that there is more nitrate formation at upstream positions relative to downstream, or from front to back of the catalyst, with short trapping times. However, as more NO X was trapped on the catalyst during longer trapping times, it was found that the largest amount of NO X was trapped slightly downstream of the inlet, evolving to a local maximum in amount trapped. Applying infrared (IR) thermography to this system resulted in a spatially resolved calorimetry method via the correlation of temperature to the distribution of sorbed nitrate species along the catalyst.

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Effect of Ceria on the Storage and Regeneration Behavior of a Model Lean NO x Trap Catalyst

Cited by 67 publications

References 16 publications

Pt/Ce Pr1−O2 (x= 1 or 0.9) NO storage–reduction (NSR) catalysts

Pt/Ce Pr1−O2 (x= 1 or 0.9) NO storage–reduction (NSR) catalysts

Effects of temperature and reductant type on the process of NOx storage reduction over Pt/Ba/CeO2 catalysts

Spatially-Resolved Calorimetry: Using IR Thermography to Measure Temperature and Trapped NOX Distributions on a NOX Adsorber Catalyst

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