摘要
研究了氦和丙烯预处理后的Re_2O_7/γ-Al_2O_3催化剂上丙烯歧化的温度效应和报导了反应后催化剂上铼离子的价态分布的XPS测定结果。氦处理后,高铼离子密度的催化剂在高温下显示较高的活性。相反,丙烯处理后低铼离子密度的催化剂在较低温度下显示较高的活性。反应后催化剂的XPS测定表明铼离子处于各种不同的价态。用丙烯处理的反应后的催化剂,其还原程度大于氦处理的经反应的催化剂。
The temperature dependence of propene metathesis over Re2O7/γ-A12O3 catalysts treated by He and/or propene, and XPS spectra of these samples were studied. After pretreated with He, catalysis with higher Re ion density show higher activity if the reaction is carried out at higher temperature. On the contrary, after propene pretreatment, the catalyst with low Re ion density displays higher activity at lower temperature. The catalyst pretreated by He shows a positive effect of the reaction temperature on its performance, but that pretreated by propene demonstrates a negative effect. XPS spectra of Re4f for the catalyst after reaction imply that the surface species are composed of Re ions in different valence states. The reductibility of the catalyst after pretreatment with propene and reaction is higher than that after pretreatment with He and reaction. But it is still not possible to confirm what species are responsible for propene metathesis over Re2O7/γ-Al2O8,
