Low Temperature NOx Adsorption Study on Pd-Promoted Zeolites

Porta, Alessandro; Pellegrinelli, Tommaso; Castoldi, L.; Matarrese, Roberto; Morandi, Sara; Dźwigaj, Stanisław; Lietti, Luca

doi:10.1007/s11244-018-1045-8

Cited by 48 publications

(38 citation statements)

References 31 publications

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“…Furthermore, ammonia cannot be delivered successfully to the catalyst at temperatures <180ºC when urea is used as the source of ammonia. In order to address the low-temperature cold start problem, Pd/zeolite materials were introduced as passive NOx adsorbers (PNA) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]. Conceptually, NOx is adsorbed at low temperature and released at temperatures when Cu/SSZ-13 is active for SCR (200ºC and higher).…”

Section: Introductionmentioning

confidence: 99%

Pd/FER vs Pd/SSZ-13 Passive NOx Adsorbers: Adsorbate-controlled Location of Atomically Dispersed Pd(II) in FER Determines High Activity and Stability

Khivantsev¹,

Wei²,

Kovařík³

et al. 2020

Preprint

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Pd-loaded FER and SSZ-13 zeolites as low-temperature passive NOx adsorbers (PNA) are compared under practically relevant conditions. Vehicle cold-start exposes the material to CO under a range of concentrations, necessitating a systematic exploration of the effect of CO on the performance of isolated Pd ions for PNA. NO release temperature of both adsorbers decreases gradually with the increase of CO concentration from a few hundred to a few thousand ppm. This beneficial effect results from local nano-“hot spots” formation during CO oxidation. Dissimilar to Pd/SSZ-13, increasing the CO concentration above ~1,000 ppm improves the NOx storage significantly for Pd/FER, attributed to the presence of a Pd ions in FER γ-site that is shielded from NOx. CO mobilizes this Pd atom to the NOx accessible position where it becomes active for PNA. This behavior explains the very high resistance of Pd/FER to hydrothermal aging: Pd/FER materials survive hydrothermal aging at 800⁰C in 10% H2O vapor for 16 hours with no deterioration in NOx uptake/release behavior. Thus, by allocating Pd ions to the specific microporous pockets in FER, we have produced very hydrothermally stable and active PNA materials with immediate practical applications.

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Section: Introductionmentioning

confidence: 99%

Pd/FER vs Pd/SSZ-13 Passive NOx Adsorbers: Adsorbate-controlled Location of Atomically Dispersed Pd(II) in FER Determines High Activity and Stability

Khivantsev¹,

Wei²,

Kovařík³

et al. 2020

Preprint

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“…[ 64–68 ] Recently, the Pd/zeolite materials (Pd/SSZ‐13, Pd/ZSM‐5, and Pd/Beta) were found possessing a high NO adsorption capacity at low temperatures. [ 10,69 ] Murata et al [ 70 ] found that Pd/ZSM‐5 possessed a high adsorption capacity of NO and HCs during a cold start on stoichiometric gasoline applications. It was suggested that NO was stored on the Pd ion sites as a nitrosyl (i.e., Pd‐NO).…”

Section: Zeolite Support Catalystsmentioning

confidence: 99%

Recent advances in catalytic automotive emission control: Passive NO storage at low temperatures

Wang

Yong

Rong

et al. 2020

J Chinese Chemical Soc

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In the practical applications, a high portion of the NO x is emitted without purification in the cold start period of engine because the selective catalytic reduction (SCR) or NO x storage and reduction (NSR) catalysts are not warmed up. Passive NO x absorbers (PNA) were proposed earlier to store the NO x at low temperatures and release the stored NO x during warm-up period when the SCR and NSR catalysts downstream are functional, while this concept just attracted great interests recently to meet the extra stringent requirement of governmental emissions regulations. A plant of PNA catalysts, showing different NO adsorption/release characteristics, was disclosed. This review summarizes the recent progress in the development of PNA catalysts. The characteristics of NO adsorption/release on precious metal (i.e., Pt, Pd) loading Al 2 O 3 support catalysts, CeO 2 support catalysts, and zeolite support catalysts are summarized and compared.

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“…This catalyst is emerging as effective passive NO x adsorbent technology because of its NO x storage/release capabilities, resistance to sulfur poisoning and hydrothermal deactivation [4][5][6][7][8]. Due to these excellent characteristics, Pd/zeolite has attracted great interest recently and has been further optimized [6][7][8][9][10][11][12][13][14][15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Various Pd Species in Pd/BEA for Cold Start Application

et al. 2019

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A series of Pd/BEA catalysts with various Pd loadings were synthesized. Two active Pd2+ species, Z−-Pd2+-Z− and Z−-Pd(OH)+, on exchanged sites of zeolites, were identified by in situ FTIR using CO and NH3 respectively. Higher NOx storage capacity of Z−-Pd2+-Z− was demonstrated compared with that of Z−-Pd(OH)+, which was caused by the different resistance to H2O. Besides, lower Pd loading led to a sharp decline of Z−-Pd(OH)+, which was attributed to the ‘exchange preference’ for Z−-Pd2+-Z− in BEA. Based on this research, the atom utilization of Pd can be improved by decreasing Pd loading.

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Low Temperature NOx Adsorption Study on Pd-Promoted Zeolites

Cited by 48 publications

References 31 publications

Pd/FER vs Pd/SSZ-13 Passive NOx Adsorbers: Adsorbate-controlled Location of Atomically Dispersed Pd(II) in FER Determines High Activity and Stability

Pd/FER vs Pd/SSZ-13 Passive NOx Adsorbers: Adsorbate-controlled Location of Atomically Dispersed Pd(II) in FER Determines High Activity and Stability

Recent advances in catalytic automotive emission control: Passive NO storage at low temperatures

Investigation of Various Pd Species in Pd/BEA for Cold Start Application

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