Steam and alkali resistant Cu-SSZ-13 catalyst for the selective catalytic reduction of NOx in diesel exhaust

Fan, Chi; Жен, Чен; Pang, Lei; Ming, Shujun; Dong, Caiyue; Albert, Kouadio Brou; Liu, Peng; Wang, Jingyu; Zhu, Dan; Chen, Hanping; Li, Tao

doi:10.1016/j.cej.2017.09.181

Cited by 97 publications

(47 citation statements)

References 41 publications

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“…To verify the intact CHA framework under SO3 poisoning, all samples were measured by XRD tests. As shown in Figure 1a, the fresh and sulfated catalysts show the typical Chabazite phase as the diffraction peaks at 9.6°, 13°, 16.3°, 18.0°, 20.9°, and 25.3° can be found [14,[31][32]. To better reveal the changes in the framework variation, the relative crystallinity was calculated using the total areas of six peaks on F-Cu as a reference, and the results are shown in Figure 1b.…”

Section: Bet and Xrd Resultsmentioning

confidence: 99%

“…Actually, a number of essential conclusions and contributions have been made to properly understand the nature of copper ions and their impact on NH 3 -SCR mechanisms over Cu/SSZ-13 catalysts [6][7][8]. When facing real applications; however, the Cu/SSZ-13 catalysts are invariably affected by impurities, like sulfur, phosphorus, or alkali metal ions, and hence, a deep comprehension of their impacts on catalysts is very useful for their application [9][10][11][12][13][14][15]. 2 of 13 Among these impurities, sulfur poisoning is a common issue in SCR catalysts [16][17][18], and even when the amount of sulfur is quite low, sulfur exposure could result in serious deactivation of SCR activity [19].…”

Section: Introductionmentioning

confidence: 99%

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The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

et al. 2019

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To reveal the role of SO 3 poisoning in Cu/SSZ-13 NH 3 -SCR catalysts, fresh and sulfated Cu/SSZ-13 catalysts were prepared in the presence or absence of SO 3 flux. The deactivation mechanism is probed by the changes of structural, copper species, and selective catalytic reduction (SCR) activity. The variations concentrate on the changes of copper species as the Chabazite (CHA) framework of Cu/SSZ-13 catalysts could keep intact at high ratios of SO 3 /SO x . The thermal gravimetric analyzer (TGA) results reveal that the copper sulfate formed during sulfation and the amounts of sulfate species increased with an increase in the SO 3 /SO x ratio. In contrast to the changing trend of copper sulfate, temperature program reduction (H 2 -TPR), and electron paramagnetic resonance (EPR) results manifest that, since the number of active copper ions declines with an increase of the SO 3/ SO x ratio, the active sites transform to these inactive species during sulfation. Due to the combination of NH 3 -SCR activity and the kinetic tests, it is shown that the decreased number of active sites is responsible for the declined SCR activity at low temperature. As Cu/SSZ-13 catalysts show excellent acid-resistance ability, our study reveals that the Cu/SSZ-13 catalyst is a good candidate for NO x elimination, especially when SO 3 exists.

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Section: Bet and Xrd Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

et al. 2019

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“…To further prove the variation of different Cu species amounts on catalysts, UV-Vis DRS spectra, a qualitative generic analysis method, was used and the results are shown in Figure 7. The band Catalysts 2018, 8, 593 7 of 15 centered at 205 nm was assigned to the oxygen-to-metal charge transfer related to Cu 2+ ions [9,15]. The 300-600 nm region was attributed to transitions in Cu x O, such as charge transfer transitions in O-Cu-O and Cu-O-Cu [4,31].…”

Section: Uv-vis Drs Resultsmentioning

confidence: 99%

“…The 300-600 nm region was attributed to transitions in Cu x O, such as charge transfer transitions in O-Cu-O and Cu-O-Cu [4,31]. In addition, the region between 600 and 800 nm was assigned to the electron d-d transitions of Cu 2+ in distorted octahedral surrounding by oxygen in CuO particles [9,15].…”

Section: Uv-vis Drs Resultsmentioning

confidence: 99%

The Role of Impregnated Sodium Ions in Cu/SSZ-13 NH3-SCR Catalysts

Wang

et al. 2018

Catalysts

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To reveal the role of impregnated sodium (Na) ions in Cu/SSZ-13 catalysts, Cu/SSZ-13 catalysts with four Na-loading contents were prepared using an incipient wetness impregnation method and hydrothermally treated at 600 • C for 16 h. The physicochemical property and selective catalytic reduction (SCR) activity of these catalysts were studied to probe the deactivation mechanism. The impregnated Na exists as Na + on catalysts and results in the loss of both Brönsted acid sites and Cu 2+ ions. Moreover, the high loading of Na ions destroy the framework structure of Cu/SSZ-13 and forms new phases (SiO 2 /NaSiO 3 and amorphous species) when Na loading was higher than 1.0 mmol/g. The decreased Cu 2+ ions finally transformed into Cu x O, CuO, and CuAlO x species. The inferior SCR activity of Na impregnated catalysts was mainly due to the reduced contents of Cu 2+ ions at kinetic temperature region. The reduction in the amount of acid sites and Cu 2+ ions, as well as copper oxide species (Cu x O and CuO) formation, led to low SCR performance at high temperature. Our study also revealed that the existing problem of the Na ions' effect should be well-considered, especially at high hydrothermal aging when diesel particulate filter (DPF) is applied in upstream of the SCR applications.Catalysts 2018, 8, 593 2 of 15 (>0.5%) mainly due to the decreased amount of isolated Cu 2+ formed CuO x clusters. Wang et al. [10] further found that alkali decreased the number of Brönsted acid sites and NH 3 coverage, and would decrease the SCR reaction rate. In our previous study [11], the different contents of Na impact on Cu/SAPO-34 were also studied. Except for the decrease of active sites and acidity, the results also showed the framework of Cu/SAPO-34 damaged and CuAlO x species formed at a high content of sodium (>0.8%), and all these factors hindered the SCR activity.In recent years, some studies have also considered the Na ions' effect on Cu/SSZ-13 catalysts, but most of them focused on co-cation Na ions. Gao et al. [12] investigated the effects of co-cation Na on Cu/SSZ-13 catalyst. They found ≈1.78% Na promoted SCR performance at low temperatures and helped to improve the hydrothermal stability of Cu/SSZ-13 because Na ions modified the redox of active sites and protected the framework of CHA structure. Zhao et al. [13] found a high amount of co-cation Na ions decreased the hydrothermal stability of Al-rich Cu/SSZ-13 at 750 • C for 5 h because the excess amount of Na ions weakened the interaction between Cu ions and the zeolitic framework and formed Cu x O species. Xie et al. [14] found one-pot-synthesized Cu/SSZ-13 with higher co-cation Na contents showed poorer hydrothermal stability at 750 • C for 16 h, which was attributed to Cu species with poor stability and CHA structure deterioration. Even though some achievements have been made on co-cation Na, the conclusion could not be applied in real-world applications because co-cation Na ions have already existed before Cu exchange and could not represent the deposition of Na in the ...

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“…The framework of the Cu-SSZ-13 catalysts in fresh, sulfated and regenerated state was characterized by XRD measurements. As shown in Figure 1, all the samples exhibited typical CHA topological structure (PDF data file 52-0784) [18][19][20]. No noticeable diffraction peaks assigned to CuO (2θ = 35.6 • and 38.8 • ) or Cu 2 O (2θ = 36.4 • ) [21] species could be observed because of the lower content of copper oxides (~3%) in our catalyst than the requirement of the laboratory-based XRD (5%).…”

Section: X-ray Powder Diffractionmentioning

confidence: 89%

Deactivation and Regeneration for the SO2-Poisoning of a Cu-SSZ-13 Catalyst in the NH3-SCR Reaction

Wang

Fan

et al. 2019

Catalysts

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Cu-SSZ-13 has been generally considered as the predominant commercial selective catalytic reduction (SCR) catalyst in the NH3-SCR reaction because of its superior activity and durability. However, in real applications, SCR catalysts readily undergo hydrothermal aging and sulfur poisoning. In this work, the deactivation and regeneration of a commercial Cu-SSZ-13 catalyst was investigated for SO2 exposures during hydrothermal aging and the effect of different regeneration temperatures was compared. By using XRD, SEM, H2-temperature programmed reduction (TPR), X–ray photoelectron spectra (XPS) and NH3-temperature programmed desorption (TPD) analysis, it was found that SO2 poisoning influenced the chabazite (CHA) structure even if regeneration cannot restore its original structure, the redox ability and ammonia storage performance also influenced by sulfation and the regeneration process. Moreover, the extent of a decrease in redox ability was more severe than acidity, suggesting that the amount of isolated Cu2+ and Cu+ reduction was responsible for irreversible deactivation over the Cu-SSZ-13 catalyst. Combined with the analysis of Ea values and pre-exponential factor of the SCR reaction, a more likely explanation for the irreversible deactivation was that active sites were lost mostly in sulfated and regenerated process sites.

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Steam and alkali resistant Cu-SSZ-13 catalyst for the selective catalytic reduction of NOx in diesel exhaust

Cited by 97 publications

References 41 publications

The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

The Role of SO3 Poisoning in CU/SSZ-13 NH3-SCR Catalysts

The Role of Impregnated Sodium Ions in Cu/SSZ-13 NH3-SCR Catalysts

Deactivation and Regeneration for the SO2-Poisoning of a Cu-SSZ-13 Catalyst in the NH3-SCR Reaction

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