Abstract
A series of mesoporous lacunary Keggin tungstoborate (BW11)/TiO2 catalysts with various BW11 contents (4%, 8% and 10%) have been prepared by encapsulation sol-gel method. These catalysts were characterized by thermogravimetric analysis (TGA/DTA), X-ray diffraction (XRD), nitrogen adsorption-desorption isotherm, scanning electron microscopy (SEM), FTIR, and UV-vis-diffuse reflectance spectroscopy. The preservation of the Keggin structure is observed up to a calcination temperature of 470 degrees C. However, around 500-600 degrees C, the BW11 structure was no longer retained. The BW11/TiO2 catalysts were investigated for the selective oxidation of styrene with hydrogen peroxide (30%) as a green oxidant. Among all the prepared catalysts, the one with 4% loading of BW11 was found to be the truly heterogeneous active catalyst with a styrene conversion of 34.3% and a high benzaldehyde selectivity over than 90%.