论文部分内容阅读
Tungsten-containing hexagonal mesoporous silica(W-HMS)supported tungsten oxide catalysts (WOx/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 WOx/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 WO3 crystallites and the oxidation of W(V)to W(VI)on the catalyst surface.Furthermore,NH3-temperature-programmed-desorption (NH3-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%WOx/W-HMS catalyst calcined at 573 K after 14 h of reaction.
Tungsten-containing hexagonal mesoporous silica (W-HMS) supported tungsten oxide catalysts (WOx / 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 WOx / 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 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 a temperature of 623 K, the catalytic activity decreased due to the presence of WO3 crystallites and the oxidation of W (V) to W (VI) on the catalyst surface. Hottermore, NH3-temperature-programmed -desorption (NH3-TPD) analysis showed that the effects of W l oading 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% WOx / W-HMS catalyst calcined at 573 K after 14 h of reaction.