A Facile Top‐Down Protocol for Postsynthesis Modification of Hierarchical Aluminum‐Rich MFI Zeolites |
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| Authors: | Lili Yu Dr. Shengjun Huang Dr. Shu Miao Fucun Chen Shuang Zhang Zhenni Liu Prof. Sujuan Xie Prof. Dr. Longya Xu |
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| Affiliation: | 1. State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road No.?457, Dalian 116023 (P. R. China);2. University of Chinese Academy of Sciences, Beijing 100049 (P. R. China) |
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| Abstract: | High aluminum content constitutes a major hurdle for the postsynthesis modification of hierarchical zeolites. A facile protocol comprising fluorination and sequential alkaline treatment is presented for the postsynthesis modification of hierarchical Al‐rich MFI zeolites. By virtue of this protocol, uniform intracrystalline mesoporosity is introduced in an Al‐rich MFI zeolite (Si/Al=14.3). The obtained hierarchical zeolites exhibit a significant mesopore size distribution, centered around 6 nm, and show improved conversions in catalytic cracking of bulky aromatic molecules. The fundamental implications of the fluorination–alkaline treatment protocol are related to the formation of F‐bearing tetrahedral aluminum species in the antecedent fluorination step, which alleviates the resistance of Al sites to the alkaline medium and causes Al?F complexation for regulated hydrolysis of the Al species during the alkaline treatment process. This top‐down protocol and the derived mechanistic understandings are expected to be applied in the synthesis of hierarchical Al‐rich zeolites with other framework topologies. |
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| Keywords: | aluminum fluorides porosity postsynthesis modification zeolites |
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