Characteristics of vanadium-substituted mesoporous silica with wormhole framework structure: effects of vanadium content |
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Authors: | Wei-Jye Wang Hsin-Yu Lin Yu-Wen Chen |
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Affiliation: | (1) Department of Chemical Engineering, Far East College, Shin-shi, 605, Tainan, Taiwan;(2) Department of Materials Science and Engineering, National Dong Hwa University, Hualien, 974, Taiwan;(3) Department of Chemical Engineering, Nanocatalysis Research Center, National Central University, Chungli, 320, Taiwan |
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Abstract: | Vanadium-substituted wormhole framework structure (V-WMS) mesoporous silicas (V-WMS) with various Si/V ratios in the range
of 15 and 200 were prepared at ambient temperature by neutral surfactant templating pathway. The materials were synthesized
by using dodecylamine as a template and tetraethylorthosilicate as a silicon source. They were characterized by energy dispersive
X-ray spectroscopy (EDS), powder X-ray diffraction (XRD), N2 adsorption–desorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy
(SEM), transmission electron microscopy (TEM), Fourier-transform infrared absorption spectroscopy (FT-IR) and ultraviolet-visible
absorption spectroscopy. V-WMS samples shown characters of larger framework wall thickness, small crystallite domain sizes,
and complementary textural mesoporosities in comparison with M41S materials. These mesoporous V-WMS samples exhibited irregularly
shaped mesoscale fundamental particles which aggregated into larger particles. They also demonstrated better thermal stability
than MCM-41. An absorption band of FT-IR at ca. 960 cm−1 was assigned to the vibration of Si–O–V linkages. These samples also showed one strong UV–visible absorbance with overlapping
maxima at about 255 nm. The results show that vanadium was incorporated into the structure of wormhole mesoporous silica (WMS).
However, for V-WMS with high vanadium content (Si/V < 25), a broad shoulder in XRD pattern was observed at about 3–4°, suggesting
the presence of impurity phase of vanadium species in the sample. The efforts in preparing V-WMS specimens by neutral-template
synthesis route had led to new mesoporous silica molecular sieves with catalytically active vanadium centers. |
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Keywords: | Mesoporous material Surfactant Hexagonal mesoporous silica Vanadium Molecular sieve |
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