Abstract: A series of WO_3/titania-alumina samples was prepared by impregnation method. The results of XRD and XPS show that WO_3 is dispersed as a monolayer on the surface of titania-alumina. The dispersion threshold is 0.22 gWO_3/(100 m~2). It approximately agrees with the value, 0.198 gWO_3/(100 m~2), calculated from the model on assuming that the WO_3 is dispersed as a elose-packed monolayer on titania-alumina surface. With LRS measurement, it can be found that as the loading of WO_3 is lower than 0.082 gWO_3/(100 m~2 titania-alumina), only distorted tetrahedral coordinated tungsten will be located on the surface, however as the loading of WO_3 is higher than 0.082 gWO_3/(100 m~2 titania-alumina), octahedral coordinated tungsten dominates. LRS measurements also show no Al_2(WO_4)_3 is formed as the WO_3/titania-alumina samples were calcined at 550 ℃. The formation of Al_2(WO_4)_3 at higher temperature also has been studied.

Key words: Tungsten oxide, Titania-alumina, Dispersion threshold, Surface structure, LRS, XPS, XRD