Investigation of the modes of NO adsorption in Pd/H-CHA

Kim, Paul M.; Mynsbrugge, Jeroen Van der; Aljama, Hassan; Lardinois, Trevor M.; Gounder, Rajamani; Head‐Gordon, Martin; Bell, Alexis T.

doi:10.1016/j.apcatb.2021.120992

Cited by 22 publications

(42 citation statements)

References 50 publications

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“…At the same time, HSE06 energies of Z 2 Pd-NO-6MR with 3NN 2Al configuration are consistent with those listed in a recent study on Pd/CHA. 62 Furthermore, coadsorption of NO with H 2 O is not predicted at the Pd ions of 2Al sites because Z 2 Pd-(H 2 O) 4 is more negative compared to Z 2 Pd-(H 2 O) 3 -NO at 400 K. Again, this result is in agreement with HSE06 calculations from the previous computational study of Pd-SSZ-13. 64 It can be concluded that no adsorption of NO at 3NN-Z 2 Pd sites is expected in the presence of H 2 O. Evidently, the PBE functional significantly exaggerates NO adsorption compared to the HSE06 functional.…”

Section: Computational Detailssupporting

confidence: 79%

“…Specifically, it has been observed previously that each isolated Pd cation stores only one NO molecule. 62 Thus, the ultimate NO/Pd molar ratio is 1. 44 In fact, many studies show NO/Pd molar ratio far below 1 9 because the synthesis of samples containing only isolated Pd cations is not a trivial task.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Thus, desorption of NO from Pd + ions is observed at higher temperatures than from Pd 2+ ions. 62 Based on PBE calculations, ZPd-OH-(H 2 O) 3 is the most stable among ZPdO x H y species under wet oxidizing conditions (O 2 and H 2 O) at temperatures between 0 and 300 K (Figures 2a and S2). ZPd-OH-H 2 O-8MR becomes the most stable at 400 K, indicating partial dehydration at these temperatures.…”

Section: Computational Detailsmentioning

confidence: 99%

“…Despite recent advances, the interpretation of PNA profiles using theoretical approaches is still contradictory. 62,64 More computational studies are needed for further development of this area. Besides Pd zeolites, zeolites ion-exchanged with other noble metals can be considered as possible PNA materials.…”

Section: Introductionmentioning

confidence: 99%

“…Previous theoretical studies on Pd zeolites used both semilocal and hybrid functionals. [62][63][64][65][66][67][68][69][70][71]84 Mei et al 67 obtained similar energies of NO adsorption in Pd-HBEA using Perdew− Burke−Ernzerhof (PBE) 85 and Heyd−Scuseria−Ernzerhof (HSE06) 86 functionals. However, Mandal et al 64 found significant dependence of NO adsorption energies on the type of exchange−correlation (XC) functional, with more exothermic NO adsorption energies for the PBE functional compared to the HSE06 functional.…”

Section: Introductionmentioning

confidence: 99%

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Computational Study of Noble Metal CHA Zeolites: NO Adsorption and Sulfur Resistance

et al. 2022

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Noble metal-exchanged small-pore molecular sieves with chabazite topology are promising materials for automotive cold-start NO x emission control applications. A combination of first-principles thermodynamics and density functional theory was applied for the prediction of monomeric palladium, platinum, and ruthenium species formed in 1Al or 2Al sites of six-/eight-membered rings of the SSZ-13 framework in the presence of SO 2 , NO, O 2 , and H 2 O at temperatures between 0 and 1100 K. Calculations using gradient-corrected Perdew−Burke−Ernzerhof (PBE) functional and hybrid Heyd−Scuseria−Ernzerhof (HSE06) functional showed that the binding energy of NO adsorbed on Pd, Pt, or Ru ions is a strong function of exchange−correlation functional. Use of the PBE functional overestimated the binding strengths of NO to Pd, Pt, or Ru ions compared to the HSE06 functional. While PBE led to the adsorption of two NO per Pd, Pt, or Ru ion, HSE06 predicted the adsorption of a single NO. Isolated Pd, Pt, or Ru ions in 1Al sites tended to bind NO stronger than their counterparts in 2Al sites. Both functionals revealed that Pd and Pt ions have more similarities in terms of both NO adsorption and sulfur resistance compared to Ru ions. The results of this study are beneficial for further modeling of passive NO x adsorbers with improved properties to deliver cleaner tailpipe emissions during engine cold start.

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Section: Computational Detailssupporting

confidence: 79%

Section: Computational Detailsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Computational Study of Noble Metal CHA Zeolites: NO Adsorption and Sulfur Resistance

et al. 2022

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Coaxial 3D Printing Enabling Mn/CHA@Pd/CHA Zeolite‐Based Core–Shell Monoliths for Efficient Passive NO_x Adsorbers

Li,

Wei,

Zhang

et al. 2024

Adv Funct Materials

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Pd‐based zeolites are extensively used as passive NOx adsorbers (PNA) for cold‐start NOx emissions to meet stringent emission regulations. However, optimizing adsorber design to reduce Pd usage with substitution by non‐noble metals that are prone to suffer from H2O remains a significant challenge. Herein, the core–shell Mn/CHA@Pd/CHA zeolite monoliths based on non‐noble metal/zeolite core are constructed using coaxial 3D printing technology and identified as efficient passive NOx adsorbers for the first time. In the Mn/CHA@Pd/CHA monolith, the Pd/CHA shell effectively protected the Mn active sites in the core from H2O, while the integration of the Mn/CHA core not only introduced efficient storage sites but also facilitated NOx desorption, thereby achieving comparable adsorption properties and increased the NOx desorption efficiency by 35% at 350 °C compared with that of Pd/CHA monolith. Furthermore, some non‐noble metal‐based zeolites (e.g., Co/CHA, Mn/MFI, Mn/BEA) and Pd‐based zeolites (e.g., Pd/AEI) are also employed as cores and shells respectively to fabricate a series of core–shell zeolite monoliths via coaxial 3D printing, highlighting the benefits of incorporating non‐noble metals into Pd‐based zeolites for improving adsorption and desorption behaviors. This work provides a promising strategy for designing cost‐effective PNA materials and contributes to improving the exhaust after‐treatment technology.

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Pd-Doped SSZ-13 for Low-T NOx Adsorption: an Operando FT-IR Spectroscopy Study

et al. 2022

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In this study, mechanistic aspects of NO adsorption/desorption over a home-made Pd/SSZ-13 passive NOx adsorber (PNA) catalyst are investigated. Operando FT-IR spectroscopy and microreactor experiments are performed to envisage the performance of the catalyst and the pathway involved in NO adsorption, with particular emphasis to the impact of species such as C3H6 and CO. In the absence of C3H6 and CO, NO is observed to adsorb as nitrosyls (anhydrous and hydrated) over both Pd2+ and Pd+ species, and as nitrates. 80 μmolNOx/gcat (NO/Pd molar ratio of 0.8) are adsorbed. The stability of nitrosyls is higher in comparison to the nitrates in that the former initially dehydrate and further decompose at elevated temperatures (> 300 °C) leading to the evolution of NO. The presence of CO and C3H6 negatively affects the amounts of NO adsorbed (53 and 45 μmolNOx/gcat, respectively) due to the reduction of Pd sites. CO admission to the catalyst forms a variety of carbonyl species over Pd2+, Pd+ and Pd0 sites which upon NO admission are readily displaced and NO is adsorbed as hydrated/anhydrous nitrosyls of Pdn+. The nitrosyls so formed exhibit lower thermal stability in comparison to nitrosyls observed in the absence of CO and decompose below 300 °C. The addition of C3H6 leads to the apparent formation of oxidized species like acetone, acrolein and acetates, besides propylene adsorption. The NO adsorption in the presence of C3H6 leads to the formation of Pdn+(NO)(X) complexes; upon heating the decomposition of this complexes is observed at low temperatures along with propylene and water desorption. Formation of organic nitro-compounds is also observed that decompose at higher temperatures.

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Investigation of the modes of NO adsorption in Pd/H-CHA

Cited by 22 publications

References 50 publications

Computational Study of Noble Metal CHA Zeolites: NO Adsorption and Sulfur Resistance

Computational Study of Noble Metal CHA Zeolites: NO Adsorption and Sulfur Resistance

Coaxial 3D Printing Enabling Mn/CHA@Pd/CHA Zeolite‐Based Core–Shell Monoliths for Efficient Passive NO_x Adsorbers

Pd-Doped SSZ-13 for Low-T NOx Adsorption: an Operando FT-IR Spectroscopy Study

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Investigation of the modes of NO adsorption in Pd/H-CHA

Cited by 22 publications

References 50 publications

Computational Study of Noble Metal CHA Zeolites: NO Adsorption and Sulfur Resistance

Computational Study of Noble Metal CHA Zeolites: NO Adsorption and Sulfur Resistance

Coaxial 3D Printing Enabling Mn/CHA@Pd/CHA Zeolite‐Based Core–Shell Monoliths for Efficient Passive NOx Adsorbers

Pd-Doped SSZ-13 for Low-T NOx Adsorption: an Operando FT-IR Spectroscopy Study

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Coaxial 3D Printing Enabling Mn/CHA@Pd/CHA Zeolite‐Based Core–Shell Monoliths for Efficient Passive NO_x Adsorbers