Effect of Si/Al ratio on catalytic performance of hydrothermally aged Cu-SSZ-13 for the NH3-SCR of NO in simulated diesel exhaust

Han, Shuai; Cheng, Jin; Chen, Zheng; Ye, Qing; Cheng, Shuiyuan; Kang, Tianfang; Dai, Hongxing

doi:10.1016/j.apsusc.2017.04.198

Cited by 96 publications

(49 citation statements)

References 40 publications

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“…Na Contents (%) 1 BET Surface Area ∆S (%) 2 F-Cu 0 792 -Na-Cu-0.3 0.7 747 5.6 Na-Cu-0. 5 1.2 737 6.9 Na-Cu-1.0 2.3 591 25.3 Na-Cu-1.…”

Section: Samples' Namementioning

confidence: 99%

“…Figure 3 shows the ex situ DRIFTs results of the fresh sample with those of Na-impregnated ones. The IR bands in the 3500-3800 cm −1 region were related to the stretching vibration modes of OH groups (-OH) [2,12,19]. IR bands at 3733 cm −1 corresponded to isolated silanols (SiOH) and at 3655 cm −1 to [Cu(OH)] + [2].…”

Section: Figurementioning

confidence: 99%

“…The IR bands in the 3500-3800 cm −1 region were related to the stretching vibration modes of OH groups (-OH) [2,12,19]. IR bands at 3733 cm −1 corresponded to isolated silanols (SiOH) and at 3655 cm −1 to [Cu(OH)] + [2]. Two strong bands at 3604 and 3580 cm −1 were assigned to the Brönsted OH groups as (Si-O(H)-Al) [2,12,19].…”

Section: Figurementioning

confidence: 99%

“…IR bands at 3733 cm −1 corresponded to isolated silanols (SiOH) and at 3655 cm −1 to [Cu(OH)] + [2]. Two strong bands at 3604 and 3580 cm −1 were assigned to the Brönsted OH groups as (Si-O(H)-Al) [2,12,19]. Moreover, the 1000-800 cm −1 region in the IR corresponded to a framework T-O-T vibration that was perturbed by the presence of exchanged Cu ions.…”

Section: Figurementioning

confidence: 99%

“…Cu/SSZ-13, one of the chabazite (CHA) zeolites with a simple topological structure, receives a lot of attention because it provides the opportunity to understand the SCR mechanism of zeolites [1]. Besides, compared with other commercial zeolites, such as ZSM-5 and BEA, Cu/SSZ-13 catalysts with outstanding NH 3 -SCR performance and hydrothermal stability are suitable for selection as a good candidate to meet the China VI emission regulation [2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

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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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“…Na Contents (%) 1 BET Surface Area ∆S (%) 2 F-Cu 0 792 -Na-Cu-0.3 0.7 747 5.6 Na-Cu-0. 5 1.2 737 6.9 Na-Cu-1.0 2.3 591 25.3 Na-Cu-1.…”

Section: Samples' Namementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Wang

et al. 2018

Catalysts

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Low‐silica Cu‐CHA Zeolite Enriched with Al Pairs Transcribed from Silicoaluminophosphate Seed: Synthesis and Ammonia Selective Catalytic Reduction Performance

et al. 2023

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Cu-exchanged low-silica CHA zeolites (Si/ Al � 4) synthesized without organic templates are promising candidate catalysts for ammonia selective catalytic reduction of nitrogen oxides (NH 3 -SCR), but their practical application is restricted due to the low hydrothermal stability. Here, inspired by the transcription from duplex DNA to RNA, we synthesized Al pairs enriched low-silica CHA zeolite (CHA-SPAEI, Si/Al = 3.7) by using silicoaluminophosphate (SAPO) featured by strict alternation of À AlÀ OÀ P(Si)À OÀ AlÀ OÀ tetrahedra as seed. The proportion of Al pairs in CHAÀ SPAEI is 78 %, which is much higher than that in the conventional low-silica CHA (CHA-LS, 52 %). After hydrothermal ageing at 800 °C for 6 h, Cu-exchanged CHA-SPAEI shows NO conversion above 90 % within 225-500 °C under a gas hourly space velocity of 200,000 h À 1 , which is much better than that of Cu-exchanged CHA-LS. The spatial close proximity of Al pairs in CHA-SPAEI is confirmed by the 27 Al double-quantum singlequantum two-dimensional NMR analyses. The strict À P(Si)À OÀ AlÀ OÀ P(Si)À O-sequence in the fragments from the dissolution of SAPO seed promotes the Al pairs with the À AlÀ OÀ SiÀ OÀ AlÀ OÀ sequence via a transcription process. The utilization of aluminophosphate-based zeolites as seeds opens up a new avenue for the regulation of the Al distribution in zeolites.

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Low‐silica Cu‐CHA Zeolite Enriched with Al Pairs Transcribed from Silicoaluminophosphate Seed: Synthesis and Ammonia Selective Catalytic Reduction Performance

et al. 2023

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Cu‐exchanged low‐silica CHA zeolites (Si/Al≤4) synthesized without organic templates are promising candidate catalysts for ammonia selective catalytic reduction of nitrogen oxides (NH3‐SCR), but their practical application is restricted due to the low hydrothermal stability. Here, inspired by the transcription from duplex DNA to RNA, we synthesized Al pairs enriched low‐silica CHA zeolite (CHA‐SPAEI, Si/Al=3.7) by using silicoaluminophosphate (SAPO) featured by strict alternation of −Al−O−P(Si)−O−Al−O− tetrahedra as seed. The proportion of Al pairs in CHA−SPAEI is 78 %, which is much higher than that in the conventional low‐silica CHA (CHA‐LS, 52 %). After hydrothermal ageing at 800 °C for 6 h, Cu‐exchanged CHA‐SPAEI shows NO conversion above 90 % within 225–500 °C under a gas hourly space velocity of 200,000 h−1, which is much better than that of Cu‐exchanged CHA‐LS. The spatial close proximity of Al pairs in CHA‐SPAEI is confirmed by the 27Al double‐quantum single‐quantum two‐dimensional NMR analyses. The strict −P(Si)−O−Al−O−P(Si)−O‐ sequence in the fragments from the dissolution of SAPO seed promotes the Al pairs with the −Al−O−Si−O−Al−O− sequence via a transcription process. The utilization of aluminophosphate‐based zeolites as seeds opens up a new avenue for the regulation of the Al distribution in zeolites.

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Effect of Si/Al ratio on catalytic performance of hydrothermally aged Cu-SSZ-13 for the NH3-SCR of NO in simulated diesel exhaust

Cited by 96 publications

References 40 publications

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

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

Low‐silica Cu‐CHA Zeolite Enriched with Al Pairs Transcribed from Silicoaluminophosphate Seed: Synthesis and Ammonia Selective Catalytic Reduction Performance

Low‐silica Cu‐CHA Zeolite Enriched with Al Pairs Transcribed from Silicoaluminophosphate Seed: Synthesis and Ammonia Selective Catalytic Reduction Performance

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