Direct incorporation of tungsten into ultra-large-pore three-dimensional mesoporous silicate framework: W-KIT-6

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.