WO3/钛铝胶体系的表面结构

WO_3/钛铝胶系列样品通过浸渍法制备. XRD 和XPS 测定结果表明WO_3单层分散在钛铝胶表面, 分散阈值为0.22 g WO_3/(100 m~2). 假定WO_3在钛铝胶表面按照密置单层模型分散, 其计算值为0.198 g WO_3/(100 m~2). 表明测定值与理论模型的计算值相接近. LRS测定表明: 当WO_3的载量低于0.082 g WO_3/(100 m~2钛铝胶)时, 只有四而体配位的钨存在; 当WO_3的载量超过0.082 g WO_3/(100 m~2钛铝胶)时, 钨主要以八面体配位存在. 同时, LRS的实验结果也表明, 550 ℃焙烧的WO_3/钛铝胶样品没有Al_2(WO_4)_3生成. 对高温焙烧条件下, Al_2(WO_4)_3的生成也进行了研究.

THE SURFACE STRUCTURE OF WO_3/TITANIA-ALUMINA SYSTEM

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.