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Synthesis and characterization of hierarchically structured aluminosilicates

Synthesis and characterization of hierarchically structured aluminosilicates. J. Mater. Chem. 2011, 21 (20), 7364-7375. Abstract. 内容： catalytically active aluminosilicate materials with hierarchical porous structures

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Synthesis and characterization of hierarchically structured aluminosilicates

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  1. Synthesis and characterization of hierarchically structured aluminosilicates . J. Mater. Chem. 2011, 21 (20), 7364-7375.

  2. Abstract • 内容：catalytically active aluminosilicate materials with hierarchical porous structures • 结构：regular array of macrochannels connected with micro-mesoporous walls(SEM&BET) • 酸性：both Brønsted and Lewis acid sites(FTIR) • 反应：esterification reaction of palmitic acid • 考察因素：composition, pH, temperature, and addition order

  3. Indroduction • Lewis acid site：the elimination of adsorbed water on Al3+sites, but could not be explained by dehydroxylation via elimination of Al-OH as such species were not detected. • Brønsted acidity：the acidity of the silanol groups was modified by the presence of neighboring Al atoms and could not be attributed to hydroxyl groups bridged between Si and Al, since such species were not detected by 1H NMR • Therefore, the authors suggested that (SiOH, Al) paired sites generate strongly acidic Brønsted acid sites, so amorphous aluminosilicates with homogeneous distribution of Si and Al would exhibit the strongest Brønsted acidity.

  4. Preparation mothod 硅源：正硅酸乙酯(TEOS)； 铝源：仲丁醇铝(TBOA)。 A typical synthesis • 4ml前驱体溶液加入40ml、一定pH溶液中(不搅拌)； • 一定温度下陈化24h； • 过滤洗涤，室温下干燥12h； • 100℃真空干燥5h； • 550℃焙烧5h。

  5. Results

  6. SEM(组成) SEM images of the hierarchical porous aluminosilicate materials from premixed alkoxides with Si/Al atomic ratios of (a) 4, (b) 1, (c) 0.25, (d) 0.

  7. EDS (组成) Quantitative X-ray elemental compositions at various regions of the aluminosilicate obtained from premixed alkoxides with Si/Al at ratio 4

  8. BET (组成)

  9. IR (组成)

  10. BET(温度)

  11. IR (温度)

  12. SEM(滴加顺序) SEM images of hierarchical porous aluminosilicate materials obtained from synthesis techniques differing in addition order of alkoxides: (a) premixed, (b) TEOS first, (c) TBOA first

  13. BET (滴加顺序)

  14. IR (滴加顺序)

  15. IR (pH)

  16. Conclusion hierarchical structures & maximum acidity Si/Al=4 acidic pH synthesis temperature of 70℃ Premix：A large percentage of the particles were macroporous TEOS fist：the macroporosity was poor TBOA first：best hierarchical structure with highest extent of macroporosity, but had lower acidity

  17. Thank you !

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