Tungsten–modified HMS catalysts for high selective oxidation of styrene with aqueous hydrogen peroxide

Tungsten-modified HMS catalysts were obtained following the oxo-peroxo and oxo-polyoxo routes by microwave heating method in presence of cetyltrimethylammonium chloride or cetylpyridine chloride as surfactants. The obtained materials were characterized by XRD, N ₂ adsorption/desorption, SEM, TEM, FTIR and Raman spectroscopy. XRD patterns at small angle exhibit a peak with differences in intensity of the reflections, significantly influenced by the method and variables of the synthesis. A typical wormhole-like pore structure of W–HMS materials, with network channels and uniform pore sizes, was observed by TEM images. The obtained tungsten-silicates were active in oxidation with hydrogen peroxide of the hydrocarbons with double bonds as styrene. The best results were obtained for the catalysts synthesized by oxo-polyoxo route, with ordered porous structure, high surface area and lower Si/W molar ratio.