Optimization, synthesis and characterization of vanadium-substituted thick-walled three-dimensional SBA-16

A systematic study was carried out to examine the viable synthesis condition at high acidic condition for the direct incorporation of a high level of vanadium into the 3D cubic arrangement of SBA-16 molecular sieves. The extent of mesopore structural ordering was determined by X-ray diffraction, N2 physisorption, SEM and TEM analysis. The coordination and nature of the V sites were characterized by FT-Raman, electron spin resonance, 29Si nuclear magnetic resonance spectroscopy, UV–visible diffuse reflectance spectroscopy and NH3–TPD analysis. The surface area of calcined V-SBA-16 was ∼1000 m2/g, while the mesopore volume of the SBA-16 cage ranged from 0.3 to 0.6 cm3g−1. The pore size distribution was ∼3.0 nm with a wall thickness of ∼9.7 nm at the maximum. The Si/V ratios as determined by ICP-OES technique was varied from 438 to 8, respectively. The calcined samples exhibited promising catalytic activity in the oxidation of styrene with tert-butyl hydroperoxide as an oxidant.