Synthesis and characterization of mesoporous, tungsten-containing molecular sieve composites

Mesoporous, tungsten-containing molecular sieve (W-SBA-15) composites were successfully synthesized via one-step hydrothermal processing using tetraethyl orthosilicate (TEOS) as the silica precursor, sodium tungstate as the tungsten precursor, and pluronic P123 triblock polymer (EO20PO70EO20, M-av = 5800) as a structure-directing reagent. The influence of various synthesis factors, such as TEOS/sodium tungstate (Si/W) molar ratios, stirring solution temperatures, TEOS pre-hydrolysis time, and crystallization temperatures, on the structure of the W-SBA-15 composite were investigated. The prepared materials were characterized by using X-ray diffraction (XRD), infrared spectroscopy (IR), diffuse reflectance ultraviolet-visible spectroscopy (DR UV-vis), scanning electron microscopy (SEM), and nitrogen adsorption-desorption measurements. The results showed that all the W-SBA-15 composite materials retained the mesopore structure of SBA-15 and the tungsten oxide species successfully substituted silica in the framework. (C) 2009 Elsevier B.V. All rights reserved.