Pd/BEA hydrocarbon traps: Effect of hydrothermal aging on trapping properties and Pd speciation

Zelinsky, Ryan; Dean, David P.; Breckner, Christian J.; Mariño, Silvia; Miller, Jeffrey T.; Epling, William S.

doi:10.1016/j.apcatb.2022.121938

Cited by 8 publications

(6 citation statements)

References 62 publications

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“…This is slightly shorter than the 2.60 Å observed for SrO. This bond contraction is often observed in single ion species bound to the support surface [39–41] . The higher shell peak in the catalysts is likely Sr−O−Al, but was too weak to reliable fit; however, the magnitude and imaginary parts of the Fourier transform do not match that of SrO.…”

Section: Resultsmentioning

confidence: 75%

The Role of Lewis Acid Sites in γ‐Al₂O₃ Oligomerization

Breckner,

Pham,

Dempsey

et al. 2023

ChemPhysChem

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Olefin oligomerization by γ-Al 2 O 3 has recently been reported, and it was suggested that Lewis acid sites are catalytic. The goal of this study is to determine the number of active sites per gram of alumina to confirm that Lewis acid sites are indeed catalytic. Addition of an inorganic Sr oxide base resulted in a linear decrease in the propylene oligomerization conversion at loadings up to 0.3 wt %; while, there is a > 95 % loss in conversion above 1 wt % Sr. Additionally, there was a linear decrease in the intensity of the Lewis acid peaks of absorbed pyridine in the IR spectra with an increase in Sr loading, which correlates with the loss in propylene conversion, suggesting that Lewis acid sites are catalytic. Characterization of the Sr structure by XAS and STEM indicates that single Sr 2 + ions are bound to the γ-Al 2 O 3 surface and poison one catalytic site per Sr ion. The maximum loading needed to poison all catalytic sites, assuming uniform surface coverage, was ~0.4 wt % Sr, giving an acid site density of ~0.2 sites per nm 2 of γ-Al 2 O 3 , or approximately 3 % of the alumina surface.

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Section: Resultsmentioning

confidence: 75%

The Role of Lewis Acid Sites in γ‐Al₂O₃ Oligomerization

Breckner,

Pham,

Dempsey

et al. 2023

ChemPhysChem

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“…This phenomenon was also observed in Pd-supported beta zeolites in other studies. 41 The experimental and simulation results demonstrated that Z 2 Pd 2+ showed higher thermal stability than Z[Pd(OH)] +. 55,56 Therefore, the direct transformation of Z 2 Pd 2+ to Z[Pd(OH)] + seems against thermodynamics and is not a rational pathway.…”

Section: Discussionmentioning

confidence: 92%

“…The same observations were made by other studies in the field. 38,40,41 However, Theis et al 42 and Shan et al 37 found that the NO storage capacity of Pd/CHA catalysts decreased as the HTA temperature increased above 800 °C. Wang et al 43 reported that Pd/SSZ-13 experienced advanced deterioration in performance upon HTA at 850 °C and 900 °C (compared to the deactivation at 800 °C).…”

Section: Introductionmentioning

confidence: 99%

Improving the hydrothermal stability of Pd/SSZ-13 for low-temperature NO adsorption: promotional effect of the Mg²⁺ co-cation

Cai

Zhao

et al. 2023

React. Chem. Eng.

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“…Further, in situ DRIFTS study was performed to investigate the Pd sites of Pd/Na-13 after phosphorus poisoning and regeneration. ,, In Figure a, the peak at 2173 cm –1 is attributed to the NO + adsorbed on the Brønsted acid sites. , The peak at 1863 cm –1 is assigned to the adsorption of NO on the Pd 2+ active sites, which are stabilized by paired Al sites, i.e., Z – Pd 2+ Z – (Z – represents the [Si–O–Al] − ). , The two adsorption peaks gradually decrease in the poisoned Pd/Na-13 with increasing phosphorus loadings (Figure a), indicating the negative effect of phosphorus on Brønsted acid sites and Pd sites. To our satisfaction, as shown in Figure b, the peaks assigned to Pd active sites are more obvious than those of Pd/Na-13 before regeneration, indicating the presence of more Pd active sites after regeneration by HTA treatment.…”

Section: Results and Discussionmentioning

confidence: 99%

“…Further, in situ DRIFTS study was performed to investigate the Pd sites of Pd/Na-13 after phosphorus poisoning and regeneration. 43,45,53 In Figure 8a, the peak at 2173 cm −1 is attributed to the NO + adsorbed on the Brønsted acid sites. 27,54 The peak at 1863 cm −1 is assigned to the adsorption of NO on the Pd 2+ active sites, which are stabilized by paired Al sites, i.e., Z − Pd 2+ Z − (Z − represents the [Si−O−Al] − ).…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Na Cocations and Hydrothermal Aging Cooperatively Boost the Regeneration of Phosphorus-Poisoned Pd/SSZ-13 for Passive NO_x Adsorption

Li,

Ding,

Hao

et al. 2023

Environ. Sci. Technol.

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Pd/SSZ-13 has been proposed as a passive NO x adsorber (PNA) for low-temperature NO x adsorption. However, it remains challenging for Pd/SSZ-13 to work efficiently when suffering from phosphorus poisoning. Herein, we report a simple and efficient strategy to regenerate the phosphorus-poisoned Pd/SSZ-13 based on the cooperation between hydrothermal aging treatment and Na cocations. It was found that hydrothermal aging treatment enabled the redispersion of Pd and P-containing species in phosphorus-poisoned Pd/SSZ-13. Meanwhile, the presence of Na cocations significantly reduced the formation of AlPO4 and retained more paired Al sites for highly dispersed Pd2+ ions, which was of great importance for the recovery of adsorption performance. To our satisfaction, the restoration ratio of the adsorption capacity of poisoned Pd/SSZ-13 was >90% after regeneration. Strikingly, the NO x adsorption activities of phosphorus-poisoned Pd/SSZ-13 with phosphorus loadings of 0.2 and 0.4 mmol g–1 almost completely recovered upon regeneration. This study demonstrates the promoting effect of Na cocations on the regeneration of phosphorus-poisoned Pd/SSZ-13 by hydrothermal aging treatment, which provides useful guidance for the design of PNA materials with excellent durability for cold-start application.

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Pd/BEA hydrocarbon traps: Effect of hydrothermal aging on trapping properties and Pd speciation

Cited by 8 publications

References 62 publications

The Role of Lewis Acid Sites in γ‐Al₂O₃ Oligomerization

The Role of Lewis Acid Sites in γ‐Al₂O₃ Oligomerization

Improving the hydrothermal stability of Pd/SSZ-13 for low-temperature NO adsorption: promotional effect of the Mg²⁺ co-cation

Na Cocations and Hydrothermal Aging Cooperatively Boost the Regeneration of Phosphorus-Poisoned Pd/SSZ-13 for Passive NO_x Adsorption

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Pd/BEA hydrocarbon traps: Effect of hydrothermal aging on trapping properties and Pd speciation

Cited by 8 publications

References 62 publications

The Role of Lewis Acid Sites in γ‐Al2O3 Oligomerization

The Role of Lewis Acid Sites in γ‐Al2O3 Oligomerization

Improving the hydrothermal stability of Pd/SSZ-13 for low-temperature NO adsorption: promotional effect of the Mg2+ co-cation

Na Cocations and Hydrothermal Aging Cooperatively Boost the Regeneration of Phosphorus-Poisoned Pd/SSZ-13 for Passive NOx Adsorption

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The Role of Lewis Acid Sites in γ‐Al₂O₃ Oligomerization

The Role of Lewis Acid Sites in γ‐Al₂O₃ Oligomerization

Improving the hydrothermal stability of Pd/SSZ-13 for low-temperature NO adsorption: promotional effect of the Mg²⁺ co-cation

Na Cocations and Hydrothermal Aging Cooperatively Boost the Regeneration of Phosphorus-Poisoned Pd/SSZ-13 for Passive NO_x Adsorption