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用XRD,XPS研究了V_2O_5在γ-Al_2O_3,SiO_2,TiO_2等载体上的分散状态,测定了最大分散容量。结果表明,V_2O_5在γ-Al_2O_3和SiO_2上能形成亚单层分散,分散容量分别为理论单层量的60％和45％;V_2O_5在TiO_2上优先形成单层,然后形成多层结构。V_2O_5在γ-Al_2O_3上分散可使表面酸性有所增加;V_2O_5在SiO_2上分散使表面酸性剧增,酸位数和表面V_(5+)的摩尔比高达0.5左右;V_2O_5在TiO_2上的负载不增加体系的表面酸性。对负载钒的分散状态及其存在形式进行了讨论。
The dispersion of V 2 O 5 on γ-Al 2 O 3, SiO 2 and TiO 2 supports was investigated by XRD and XPS. The maximum dispersion capacity of V 2 O 5 was determined. The results show that V 2 O 5 can form sub-monolayer dispersion on γ-Al 2 O 3 and SiO 2 with dispersion capacities of 60% and 45% of theoretical monolayers, respectively. V 2 O 5 preferentially forms single layer on TiO 2 and then forms multi-layer structure. The dispersion of V 2 O 5 on γ-Al 2 O 3 can increase the surface acidity. The dispersion of V 2 O 5 on SiO 2 increases the surface acidity sharply, and the molar ratio of acid sites to the surface V 5+ is as high as 0.5. The loading of V 2 O 5 on TiO 2 Increase the surface acidity of the system. The dispersion of vanadium and its existing forms were discussed.