期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 25, 期 11, 页码 2675-2683出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201802912
关键词
aluminosilicates; dealumination; desilication; mesopore engineering; shielding effects
资金
- Natural Science Foundation of China [21776272]
Desilication has been proven an effective approach for the construction of well-defined hierarchical porosities inside zeolites with an optimal framework Al content (Si/Al=25-50). However, for the Al-rich aluminosilicate zeolites, desilication is constrained by the excess and extensive shielding effects from high Al-contents. The developments in the desilication of siliceous zeolites convey a simplified principle of controlled dissolution of the microporous matrix for the construction of hierarchical porosities, which benefits the innovation of synthetic approaches for Al-rich zeolites. The perturbations to the environments of framework Al species may alleviate the excess shielding effects. This review highlights two corresponding protocols of sequential fluorination-desilication and steaming-desilication for the construction of hierarchical porosities inside Al-rich ZSM-5 zeolites. The success of these two protocols revitalizes the prevailing understanding of the interplay between dealumination and desilication, and implies the necessity of investigating the overlooked roles of extra-framework Al species. Despite the long history and significant achievements in the last decade, fundamental understandings at the molecule level are still limited for the desilication-based top-down approaches. In particular, the investigations on Al-rich zeolites just find their growing. The bridging of dealumination and desilication is essential for other industrially relevant Al-rich zeolites (e.g., faujasite zeolites). The complexities in the inherent characters (topology, spatial distribution, proximity, etc.) and apparent parameters (morphology, crystal/particle size, etc.) demand constructive synthetic toolboxes and further fundamental understanding.
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