Importance of controllable Al sites in CHA framework by crystallization pathways for NH3-SCR reaction

Zhang, Juan; Shan, Yulong; Zhang, Ling; Du, Junjie; He, Hong; Han, Shichao; Lei, Chi; Wang, Qianqian; Fan, Weibin; Feng, Zhaochi; Liu, Xiaolong; Meng, Xiangju; Xiao, Feng‐Shou

doi:10.1016/j.apcatb.2020.119193

Cited by 53 publications

(31 citation statements)

References 48 publications

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“…Isolated Cu 2+ species in the CHA configuration are often considered to be the major active sites for the SCR reaction. 1,21 As shown in Fig. 5, Cu-CHA USY -0.40 exhibits a wider temperature window than Cu-CHA USY -0.25, because the former has more Cu 2+ species than the latter.…”

Section: Resultsmentioning

confidence: 95%

“…This is because 6MR has been considered as the key site for the location of copper ions which are active sites for catalyzing the NH 3 -SCR reaction. 21 As shown in Fig. 3, there are two possible arrangements including Al–Si–Al (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…20 Therefore, the key to CHA zeolite preparation via interzeolite transformation without using an organic template showing excellent NH 3 -SCR activity is the construction of a suitable framework that facilitates the dispersion and function of the active copper species. 21…”

Section: Introductionmentioning

confidence: 99%

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Understanding the superior NH₃-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Sun

Wang

et al. 2022

Inorg. Chem. Front.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

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Understanding the superior NH₃-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Sun

Wang

et al. 2022

Inorg. Chem. Front.

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“…Iorio et al found that the density of paired Al increased linearly with the Na + content incorporated into the crystallized solid when using TMAda + and Na + as organic and inorganic SDA [ 18 , 19 ]. Zhang et al also increased the amounts of close Al sites in SSZ-13 by adjusting the crystallization pathways using DMCHA + as the organic template, generating more Cu 2+ -2Al species than found in Cu-SSZ-13 synthesized using TMAda + as the organic template [ 20 ].…”

Section: Introductionmentioning

confidence: 99%

“…used a solvent-free method to successfully synthesize SSZ-13 substrate by using economical N,N,N-dimethylethylcyclohexylammonium bromide (DMCHABr) as an organic template to achieve 95.7% of efficiency of silica source usage. Interestingly, the Cu 2+ ion-exchanged SSZ-13 synthesized using DMCHABr as a template showed higher HTS than Cu-SSZ-13 synthesized by the traditional method using TMAdaOH as a template, since more spatially close Al sites (favouring Cu 2+ -2Z as elaborated in ‘Hydrothermal stability’ section) exist in the former Cu-SSZ-13 [ 20 , 90 ]. Furthermore, seed-assisted rapid synthesis of SSZ-13 through interzeolite transformation from FAU zeolite was achieved in the absence of solvent, which shortened the crystallization time to 1 day [ 91 ].…”

Section: Introductionmentioning

confidence: 99%

Selective catalytic reduction of NOx with NH3: opportunities and challenges of Cu-based small-pore zeolites

Shan

Zhang

et al. 2021

National Science Review

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164

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Zeolites, as efficient and stable catalysts, are widely used in the environmental catalysis field. Typically, Cu-SSZ-13 with small-pore structure shows excellent catalytic activity for selective catalytic reduction of NOx with ammonia (NH3-SCR) as well as high hydrothermal stability. This review summarizes major advances in Cu-SSZ-13 applied to the NH3-SCR reaction, including the state of copper species, standard and fast SCR reaction mechanism, hydrothermal deactivation mechanism, poisoning resistance, and synthetic methodology. The review gives a valuable summary of new insights on the matching between SCR catalyst design principles and the characteristics of Cu2+-exchanged zeolitic catalysts, highlighting the significant opportunity presented by zeolite-based catalysts. Principles for designing zeolites with excellent NH3-SCR performance and hydrothermal stability are proposed. On the basis of these principles, more hydrothermally stable Cu-AEI and Cu-LTA zeolites are elaborated as well as other alternative zeolites applied to NH3-SCR. Finally, we call attention to the challenges facing Cu-based small-pore zeolites that still need to be addressed.

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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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Importance of controllable Al sites in CHA framework by crystallization pathways for NH3-SCR reaction

Cited by 53 publications

References 48 publications

Understanding the superior NH₃-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Understanding the superior NH₃-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Selective catalytic reduction of NOx with NH3: opportunities and challenges of Cu-based small-pore zeolites

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

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Importance of controllable Al sites in CHA framework by crystallization pathways for NH3-SCR reaction

Cited by 53 publications

References 48 publications

Understanding the superior NH3-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Understanding the superior NH3-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Selective catalytic reduction of NOx with NH3: opportunities and challenges of Cu-based small-pore zeolites

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

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Understanding the superior NH₃-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation

Understanding the superior NH₃-SCR activity of CHA zeolite synthesized via template-free interzeolite transformation