摘要
用程序升温还原(TPR)方法研究了不同组成V_2O_5-SnO_2样品的还原性能,并对不同还原阶段样品进行了X射线衍射(XRD)及电子顺磁共振(EPR)测定。结果提供了还原过程中物相及钒离子价态变化的信息,发现由于钒离子在SnO_2中的高度分散及组分间的相互作用,V^(5+)的还原温度比纯V_2O_5有明显降低,说明V_2O_5-SnO_2二元氧化物体系比V_2O_5更易获得电子,上述现象与V_2O_5-SnO_2样品作为甲苯选择氧化催化剂所表现的相当高的活性密切相关。
The reducibility of V2O5-SnO2 catalyst samples with different composition was studied by temperature-programmed reduction. In order to understand the change of phases and valence states of vanadium ions in the reduction process, XRD and EPR experiments were performed at several different reduction stages. The results showed that the temperature at which vanadium ions of V2O6-SnO2 samples reduced was much lower than that of V2O5. It means that the electrons can be more easily obtained by V2O5-SnO2 catalysts than by V2O5. According to the analysis of the TPR profiles of V2O5-SnO2 samples, it was suggested that the properties of easily reduced vanadium ions of the V2O5-SnO2 samples were caused by the promotion action of SnO2 and the high dispersion of vanadium ions in SnO2. The phenomena were related to the high activity of V2O5-SnO2 catalyst with composition of V:Sn = 1:2.1 (atomic ratio) in the oxidation of toluene.
基金
南京大学现代分析中心测试基金
