synthesis and characterization of hierarchically structured aluminosilicates

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Synthesis and characterization of hierarchically structured

aluminosilicates

J. Mater. Chem. 2011, 21 (20), 7364-7375.

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

Abstract

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.

Indroduction

硅源：正硅酸乙酯 (TEOS)；铝源：仲丁醇铝 (TBOA)。A typical synthesis4ml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。

Preparation mothod

Results

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.

EDS (组成 )

Quantitative X-ray elemental compositions at various regions ofthe aluminosilicate obtained from premixed alkoxides with Si/Al at ratio 4

BET (组成 )

IR (组成 )

BET(温度 )

IR (温度 )

SEM(滴加顺序 )

SEM images of hierarchical porous aluminosilicate materialsobtained from synthesis techniques differing in addition order of alkoxides: (a) premixed, (b) TEOS first,(c) TBOA first

BET (滴加顺序 )

IR (滴加顺序 )

IR (pH)

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 poorTBOA first ： best hierarchical structure with highest extent of macroporosity, but had lower acidity

Conclusion

Thank you !