Correlation of the changes in the framework and active Cu sites for typical Cu/CHA zeolites (SSZ-13 and SAPO-34) during hydrothermal aging

The relative framework stability of Cu/CHA zeolites (SAPO-34 and SSZ-13) was studied during hydrothermal aging at 800 °C, and the fundamental mechanism for the framework change was investigated. Additionally, the relationship between the variation in the framework and active SCR reaction sites was e...

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Published inPhysical chemistry chemical physics : PCCP Vol. 17; no. 43; pp. 29142 - 29149
Main Authors Su, Wenkang, Li, Zhenguo, Peng, Yue, Li, Junhua
Format Journal Article
LanguageEnglish
Published England 01.01.2015
Subjects
Agglomeration
Crystal defects
Crystallinity
Detaching
Migration
Stability
Transformations
Zeolites
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Summary:The relative framework stability of Cu/CHA zeolites (SAPO-34 and SSZ-13) was studied during hydrothermal aging at 800 °C, and the fundamental mechanism for the framework change was investigated. Additionally, the relationship between the variation in the framework and active SCR reaction sites was established. SAPO-34 showed stronger stability during hydrothermal aging than SSZ-13. The results showed that dealumination occurred in the SSZ-13 zeolite, leading to the loss of crystallinity and a severe decrease of the Brönsted acid sites. Simultaneously, the detached Al(OH)3 species deactivated the Cu species by the transformation of isolated Cu(2+) ions to CuAlOx species. While the vacancy in the SAPO-34 framework caused by desilication could be healed with the migration of extra-framework Al and P atoms to the defects. And the Cu species showed a certain degree of aggregation with the improved redox ability of the aged Cu/SAPO-34 zeolite and the acidic properties were well maintained.
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ISSN:1463-9076
1463-9084
DOI:10.1039/c5cp05128b