Direct incorporation of tungsten into ultra-large-pore three-dimensional mesoporous silicate framework: W-KIT-6
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Tungsten was incorporated into ultra-large-pore silicate, KIT-6, via hydrothermal synthesis method using a Pluronic P123 triblock copolymer as the structure directing agent and n-butanol as additive. The Si/W ratio in the synthesis gel was varied from 10 to 100. Calcined W-KIT-6 samples were characterized by XRD, elemental analysis, N2 sorption, HR-TEM, XPS, DR-UV-Vis, H2-TPR and NH3-TPD. These samples possess surface areas ranging from 625 to 927 m2/g with corresponding pore volumes from 1.09 to 1.44 cm3/g and narrow pore size distributions from 6.3 to 6.9 nm. In all the samples, the framework incorporation of tungsten is evident from low angle XRD and DR-UV-Vis analyses. In samples with higher tungsten content, extra-framework WO3 species were also evident from high angle XRD, Laser Raman and DR-UV-Vis studies. NH3-TPD study revealed the presence of low to medium acid strength sites in these samples.
KeywordsKIT-6 Tungsten Hydrothermal synthesis Mesoporous Acidity
We gratefully acknowledge support from CEBC funds and the expert assistance provided by David Moore and Heather Shinogle in obtaining the TEM and SEM images. Dr. Daniel Resasco’s group at the University of Oklahoma is acknowledged for SAXS and XPS analysis.
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