【摘要】 应用X光衍射法（XRD）测定了WO₃/γ-Al₂O₃体系的物相组成和平均晶粒度,以及该体系的孔容和比表面;应用XRD相定量外推法和光电子能谱（XPS）峰强度比(I_W4f/I_Al2s法定量测定了WO₃在γ-Al₂O₃表面的最大分散量,测值分别为0.21和0.20gWO₃/100m²γ-Al₂O₃,与按照WO₃在γ-Al₂O₃表面作密置单层排布模型的计算值(0.189gWO₃/100m²,即4.9×10¹⁸W原子/m²)相近。对WO₃/γ-Al₂O₃体系与MoO₃/γ-Al₂O₃体系作了比较和讨论。更多还原

【Abstract】 The maximum monolayer dispersion （the threshold） for WO₃ on γ-Al₂O₃ calcined at 500℃, 550℃, 600℃ and 640℃ has been determined quantitatively by XRD （amount of crystalline phase） and XPS （intensity ratios W 4f/Al 2s）. The results show that if the amount of WO₃ loaded is lower than the maximum monolayer dispersion, WO₃ will react with γ-Al₂O₃ to form surface compound due to mutual ionic interaction, and will be dispersed on γ-Al₂O₃ surface as monolayer then. In case the amount is higher than this value, the residual crystalline WO₃ will remain. The maximum monolayer dispersion （threshold） is 0.21 and 0.20g WO₃/100m² γ-Al₂O₃ by XRD and XPS respectively. It agrees with the value (0.189g WO₃/100m² or 4.90×10¹⁸ W atoms/m²) calculated from the model on assumption that the WO₃ is despersed as a closed-packed monolayer on γ-Al₂O₃ surface. Inasmuch as WO₃/-Al₂O₃ system is stable up to higher temperature, e. g. 700℃, than MoO₃/γ-Al₂O₃ system, WO₃ seems unfavorable to form new bulk compound with γ-Al₂O₃ at that temperature. However, Al₂（MoO₄）₃ forms perceptibly in MoO₃/γ-Al₂O₃ system at 500℃. Besides, the size of residual cryatalline WO₃ in WO₃/γ-Al₂O₃ is much smaller than that of MoO₃ in MoO₃/γ-Al₂O₃. It might be the reason that WO₃/γ-Al₂O₃ catalyst is superior to MoO₃/γ-Al₂O₃ in hydrodesulfurization or hydrodenitrogenation in some cases.更多还原