Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: <i>in situ</i> Cu and S K-edge XAS studies

Mesilov, V. V.; Dahlin, Sandra; Bergman, Susanna L.; Hammershøi, Peter S.; Xi, Shibo; Pettersson, Lars J.; Bernasek, S. L.

doi:10.1039/d1cy00975c

Cited by 4 publications

(18 citation statements)

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“…This sequence of experiments likely changed the reduction behavior of the Cu species. This is in line with our previous studies on the regeneration of Cu-SSZ-13 where sulfur-free Cu species of desulfated catalysts showed condition-dependent behavior, which is different from what is observed for the fresh catalysts. , …”

Section: Discussionsupporting

confidence: 90%

“…The XANES of PC5 shows a higher intensity of the white line and a shift of the white line maximum to lower energies as compared to that seen for PC4 (Figure ). The differences in white line shape of PC4 and PC5 can indicate variations in charge transfer processes between Cu ions and their surrounding ligands. , An increased intensity of the postedge feature at around 9015 eV is also observed (inset of Figure ). Nevertheless, PC5 does not exhibit the rising-edge shoulder, which is observed for PC4.…”

Section: Resultsmentioning

confidence: 95%

“…Overall, PC6 can be attributed to the precursor of PC2 because a transformation of PC6 to PC2 is observed for A-Cu. Two different Cu I ions during reduction of Cu-SSZ-13 have also been considered previously . Because PC6 shows a pronounced region at 8983 eV, it can be associated with quasi-linear Cu I .…”

Section: Resultsmentioning

confidence: 99%

“…Abundant studies on sulfur poisoning of Cu-SSZ-13 have been performed. − The sulfur poisoning led to decreased deNO x activity at temperatures below 350 °C . This deactivation was mainly associated with the poisoning of active Cu sites .…”

Section: Introductionmentioning

confidence: 99%

“…Although Cu-SSZ-13 catalysts have been widely investigated using Cu K-edge X-ray absorption spectroscopy (XAS), − there are only a few XAS studies concerning sulfur-poisoned catalysts. − Shih et al found a higher fraction of nonreduced Cu II for poisoned catalysts in NO/NH 3 as compared to fresh catalysts. In addition to a suppressed reduction of Cu ions, we also found decreased mobility of Cu ions in the S-poisoned catalyst .…”

Section: Introductionmentioning

confidence: 99%

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Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

et al. 2022

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Biodiesel is a promising renewable fuel, which may help to limit our dependence on fossil fuels. However, the presence of contaminants in biodiesel can affect the Cu speciation of the Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, resulting in its deactivation and decreased durability. In situ Cu K-edge X-ray absorption fine structure (XAFS) scanning during a temperature-programmed reduction in hydrogen (H2-TPR) has been applied here for the analysis of Cu speciation in Cu-SSZ-13 catalysts aged using pure and contaminated biodiesel fuels. XAFS data were analyzed using the multivariate curve resolution alternating least-squares (MCR-ALS) method. While only reduction from CuII to CuI was observed at temperatures below 500 °C for the catalyst aged using pure biodiesel, a one-step reduction of CuII to Cu0 at temperatures between 400 and 500 °C was found for the catalyst aged using P-doped biodiesel. The transformation of isolated CuII species to CuII clusters was suggested for the catalyst as a result of aging using P-doped biodiesel. The catalyst aged using S-doped biodiesel showed mainly the reduction of isolated CuII to CuI, which was inhibited as compared to that observed for the catalyst aged using pure biodiesel. The reduction of the catalyst aged using P+S-doped biodiesel led to the reduction of CuII to both CuI and Cu0. The phosphorus was responsible for the formation of CuII clusters during aging of the catalyst using P+S-doped biodiesel. This study reveals that the presence of phosphorus in biofuels should be strictly regulated to avoid major changes in the Cu speciation of Cu-SSZ-13 catalysts.

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Section: Discussionsupporting

confidence: 90%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

et al. 2022

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Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Mesilov

Zhuang

et al. 2023

J. Phys. Chem. C

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Biodiesel is an environmentally friendly fuel that may partially replace petroleum diesel in transportation. One possible disadvantage of biodiesel is that alkali and alkaline earth metals can significantly affect Cu speciation and the elemental composition of copper chabazite (Cu-CHA) catalysts used in vehicle emission control units. To investigate this, we perform atomic-scale characterization of Cu-SSZ-13 zeolites contaminated by Mg, K, and Na using inductively coupled plasma-optical emission spectroscopy and Cu K-edge X-ray absorption spectroscopy (XAS) coupled with hydrogen temperature-programmed reduction. The experimental data decomposed by a multivariate curve resolution algorithm are interpreted using theoretical XAS spectra and reactive molecular dynamics. We find that Mg poisoning leads to a more severe dealumination compared to K or Na poisoning. Poisoning of catalysts also leads to the aggregation of isolated Cu ions into CuO x clusters, while alkali and alkaline earth metal ions replace Cu ions in ion-exchange sites. The site preferences of Mg, K, and Na ions in Cu-CHA are thoroughly explored using density functional theory (DFT) calculations, suggesting an explanation of results from elemental analysis. Our study provides important theoretical and experimental insights into the poisoning of Cu-CHA catalysts by biodiesel metal contaminants.

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Effect of SO₂ and SO₃ Exposure to Cu-CHA on Surface Nitrate and N₂O Formation for NH₃–SCR

Han,

Bjerregaard,

Grönbeck

et al. 2024

ACS Eng. Au

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We report effects of SO2 and SO3 exposure on ammonium nitrate (AN) and N2O formation in Cu-CHA used for NH3–SCR. First-principles calculations and several characterizations (ICP, BET, XRD, UV–vis–DRS) were applied to characterize the Cu-CHA material and speciation of sulfur species. The first-principles calculations demonstrate that the SO2 exposure results in both (bi)sulfite and (bi)sulfate whereas the SO3 exposure yields only (bi)sulfate. Furthermore, SOx adsorption on framework-bound dicopper species is shown to be favored with respect to adsorption onto framework-bound monocopper species. Temperature-programmed reduction with H2 shows two clear reduction states and larger sulfur uptake for the SO3-exposed Cu-CHA compared to the SO2-exposed counterpart. Temperature-programmed desorption of formed ammonium nitrate (AN) highlights a significant decrease in nitrate storage due to sulfur species interacting with copper sites in the form of ammonium/copper (bi)bisulfite/sulfate. Especially, highly stable sulfur species from SO3 exposure influence the NO2–SCR chemistry by decreasing the N2O selectivity during NH3–SCR whereas an increased N2O selectivity was observed for the SO2-exposed Cu-CHA sample. This study provides fundamental insights into how SO2 and SO3 affect the N2O formation during ammonium nitrate decomposition in NH3–SCR applications, which is a very important topic for practical applications.

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Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: in situ Cu and S K-edge XAS studies

Abstract: In situ Cu and S K-edge X-ray absorption spectroscopy (XAS) was used for the investigation of sulfur-poisoned and regenerated Cu-SSZ-13 selective catalytic reduction (SCR) catalysts. Sulfur in the oxidation state...

Cited by 4 publications

References 111 publications

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Effect of SO₂ and SO₃ Exposure to Cu-CHA on Surface Nitrate and N₂O Formation for NH₃–SCR

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Insights into sulfur poisoning and regeneration of Cu-SSZ-13 catalysts: in situ Cu and S K-edge XAS studies

Abstract: In situ Cu and S K-edge X-ray absorption spectroscopy (XAS) was used for the investigation of sulfur-poisoned and regenerated Cu-SSZ-13 selective catalytic reduction (SCR) catalysts. Sulfur in the oxidation state...

Cited by 4 publications

References 111 publications

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H2-TPR

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H2-TPR

Poisoning of Copper Chabazite Catalyst by Biodiesel Metal Contaminants: Effect of Alkali and Alkaline Earth Metals

Effect of SO2 and SO3 Exposure to Cu-CHA on Surface Nitrate and N2O Formation for NH3–SCR

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Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Effect of SO₂ and SO₃ Exposure to Cu-CHA on Surface Nitrate and N₂O Formation for NH₃–SCR