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首次用PASCA(化学分析正电子谱)及磁天平技术研究WO_3在_2γ-Al_2O_3表面的分散过程及γ-Al_2O_3的表面性质。结果表明:WO_3在γ-Al_2O_3表面最大单层分散量为0.120g WO_3/100m~2。这一结果只相当于文献报导理论值(0.189g WO_3/100m~2)的64％。还发现γ-Al_2O_3表面存在强和弱两类不同的中心:Sk和Sts,它们分别与WO_3作用生成不同稳定程度的“表面相互作用复合物”:WO_3-Sk和WO_3-Sts。提出γ-Al_2O_3表面可划分为两个区域:可吸附区A和隐蔽区S。这两个区域的比例大小既取决于γ-Al_2O_3本身的性质,也取决于吸附分子的性质及大小。WO_3首先吸附在可吸附区A中表面能最高的Sk中心上,然后再吸附到表面能较低的Sts中心,直到铺满整个可吸附区为止。
The dispersion process of WO_3 on _2γ-Al_2O_3 surface and the surface properties of γ-Al_2O_3 were studied for the first time using PASCA (chemical analysis of positron emission spectroscopy) and magnetic balance technique. The results show that the maximum monolayer dispersion of WO 3 on γ-Al 2 O 3 surface is 0.120g WO_3 / 100m ~ 2. This result is only equivalent to 64% of the reported theoretical value (0.189g WO_3 / 100m ~ 2). It is also found that there are two kinds of strong and weak centers: Sk and Sts on the surface of γ-Al 2 O 3, which respectively produce “surface-interacting complexes” of different stability with WO 3: WO_3-Sk and WO_3-Sts. The γ-Al 2 O 3 surface can be divided into two regions: adsorbable region A and concealed region S. The ratio of these two regions depends on both the nature of γ-Al 2 O 3 itself and the nature and size of the adsorbed molecules. WO_3 first adsorbed on the highest surface energy Sk center in the adsorbable zone A, and then adsorbed onto the center of the lower surface energy Sts until it covered the entire adsorbable zone.