Characterization of Tungsten-Based Catalyst Used for Selective Oxidation of Cyclopentene to Glutaraldehyde

Abstract

Tungsten-containing hexagonal mesoporous silica (W-HMS) supported tungsten oxide catalysts (WO x /W-HMS) was prepared for the selective oxidation of cyclopentene with aqueous hydrogen peroxide to glutaraldehyde. X-ray diffraction (XRD) results indicated that the crystal form of the active phase (tungsten oxide) of the WO x /W-HMS catalysts was dependent on the W loading and calcination temperature. X-ray photoelectron spectroscopy (XPS) analysis revealed that the dispersed tungsten oxides on the surface of W-HMS support consisted of a mixture of W(V) and W(VI). It was found that a high content of amorphous W species in (5+) oxidation state resulted in the high catalytic activity. When the W loading was up to 12% (by mass) or the catalyst precursor was treated at temperature of 623 K, the catalytic activity decreased due to the presence of WO 3 crystallites and the oxidation of W(V) to W(VI) on the catalyst surface. Furthermore, NH 3-temperature-programmed-desorption (NH 3-TPD) analysis showed that the effects of W loading and calcination temperature on the acidity of the catalysts were related to the catalytic activity. A high selectivity of 80.2% for glutaraldehyde with a complete conversion of cyclopentene was obtained over 8%WO x /W-HMS catalyst calcined at 573 K after 14 h of reaction.