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Title: A merit synthesis of well-ordered two-dimensional mesoporous niobium silicate materials with enhanced hydrothermal stability and catalytic activity
Authors: Selvaraj, M.
Kawi, S. 
Park, D.W.
Ha, C.S.
Issue Date: 7-May-2009
Citation: Selvaraj, M., Kawi, S., Park, D.W., Ha, C.S. (2009-05-07). A merit synthesis of well-ordered two-dimensional mesoporous niobium silicate materials with enhanced hydrothermal stability and catalytic activity. Journal of Physical Chemistry C 113 (18) : 7743-7749. ScholarBank@NUS Repository.
Abstract: An environmentally friendly and efficient hydrothermal method has been used for the synthesis of mesoporous NbSBA-15 materials. To find better hydrothermal stability, the synthesized NbSBA-15 materials have been treated in boiling water and water steam at different temperatures with various times. The NbSBA-15 materials have been characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), N2 adsorption, UV-visible diffuse reflectance spectroscopy (UV-vis DRS), field emissionscanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). To investigate the effect of structural and textural properties with a higher Nb incorporation, NbSBA-15 has also been synthesized at different pH in sol-gel solution. The results of ICP-AES, TEM-EDS, and XPS show that a n Si/nNb ratio up to 6.7 is successfully prepared by changing the nSi/nNb ratio in the synthesis gel at pH 2.2. For all calcined NbSBA-15 materials, XRD reflection peaks shift to lower angle with increasing Nb content, resulting in the increase of the unit cell parameter. With increase in the incorporation of Nb in the framework of SBA-15, nitrogen adsorption measurement shows that the pore diameter of NbSBA-15 increases from 71.7 to 75.0 Å, the pore volume increases from 1.22 to 1.24 cm3/g with increasing surface area from 788 to 945 m2/g, and pore wall thickness increases from 32.3 to 35.13 Å. UV-vis DRS and XPS measurements show that not only the synthesized NbSBA-15(2.2pH) has a superior hydrothermal stability but also a higher amount of tetrahedral Nb5+ species is incorporated into SBA-15 with well-ordered mesoporous structure. TEM and FE-SEM images show the uniform pore diameter and ropelike hexagonal mesoporous structure of NbSBA-15. Furthermore, the NbSBA- 15 materials have been used as the catalysts for epoxidation of cis-cyclooctene, and in this study, NbSBA- 15(2.2pH) has a higher catalytic activity. © 2009 American Chemical Society.
Source Title: Journal of Physical Chemistry C
ISSN: 19327447
DOI: 10.1021/jp811334r
Appears in Collections:Staff Publications

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