synthesis and characterization of hierarchically structured aluminosilicates
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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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 !