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  Exploring Meso-/Microporous Composite Molecular Sieves with Core–Shell Structures

Qian, X. F., Li, B. S., Hu, Y. Y., Niu, G. X., Zhang, D. Y. H., Che, R. C., et al. (2012). Exploring Meso-/Microporous Composite Molecular Sieves with Core–Shell Structures. Chemistry-a European Journal, 18(3), 931-939. doi:10.1002/chem.201102505.

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 Urheber:
Qian, Xufang F.1, Autor
Li, Bing Sen1, Autor
Hu, Yuanyuan Y.1, Autor
Niu, Guoxing X.1, Autor
Zhang, D. Yahong H.1, Autor
Che, Renchao C.1, Autor
Tang, Yi1, Autor
Su, Dang Sheng2, 3, Autor           
Asiri, Abdullah M.4, Autor
Zhao, Dongyuan4, Autor
Affiliations:
1Department of Chemistry, Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Laboratory of Advanced Materials, Fudan University, 200433 Shanghai (P.R. China), ou_persistent22              
2Shenyang National Laboratory for Materials Science Institute of Metal Research, Chinese Academy of Science, ou_persistent22              
3Inorganic Chemistry, Fritz Haber Institute, Max Planck Society, ou_24023              
4Chemistry Department and the Center of Excellence for Advanced Materials Research, Faculty of Science, King Abdulaziz University, P. O. Box 80203, Jeddah (Saudi Arabia), ou_persistent22              

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Schlagwörter: composite materials; core–shell structures; mesoporous materials; molecular sieves; zeolites
 Zusammenfassung: A series of core–shell-structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM-5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant-directed sol–gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15–100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso-/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4–3.0 nm in diameter) to zeolite micropores (≈0.51 nm). The short-time kinetic diffusion efficiency of benzene molecules within pristine ZSM-5 (≈7.88×10−19 m2 s−1) is almost retainable after covering with 75 nm-thick mesoporous silica shells (≈7.25×10−19 m2 s−1), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core–shell composite shows greatly enhanced adsorption capacity (≈1.35 mmol g−1) for large molecules such as 1,3,5-triisopropylbenzene relative to that of pristine ZSM-5 (≈0.4 mmol g−1) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core–shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Brønsted acid sites). The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core–shell structure over pristine ZSM-5. Insight into the core–shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes.

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Sprache(n): eng - English
 Datum: 2011-12-142012-01-16
 Publikationsstatus: Erschienen
 Seiten: -
 Ort, Verlag, Ausgabe: -
 Inhaltsverzeichnis: -
 Art der Begutachtung: Expertenbegutachtung
 Identifikatoren: DOI: 10.1002/chem.201102505
 Art des Abschluß: -

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Titel: Chemistry-a European Journal
  Andere : Chem.-Eur. J.
Genre der Quelle: Zeitschrift
 Urheber:
Affiliations:
Ort, Verlag, Ausgabe: Weinheim, Germany : VCH Verlagsgesellschaft
Seiten: - Band / Heft: 18 (3) Artikelnummer: - Start- / Endseite: 931 - 939 Identifikator: ISSN: 0947-6539
CoNE: https://pure.mpg.de/cone/journals/resource/954926979058