ZrO2催化剂表面Zr3+离子与F-T反应中异丁烯选择性的相关性

研究了ZrO2催化剂体系中的CO加氢反应，并对催化剂的使用前后以及特殊处理催化剂进行了EPR表征，在使用前催化剂中观测到了一个较强的EPR信号g⊥＝1.976和g||＝1.961，并指认为来自ZrO2表面的Zr3 离子，而F－T反应评价后催化剂均给出了唯一较强和尖锐的信号g＝2．0024并指认为来自催化剂表面的解离H原子．通过进一步的EPR表征，结果均显示Zr3 离子可能参与了反应过程．定量研究表明，催化剂表面Zr3 离子浓度与反应中异丁烯的选择性有一近似的线性关系.最后，推测了依其表面物种Zr（Ⅲ）（CO）2形成异丁烯的可能催化机理．

Correlation Between the Catalytic Property and Zr~(3 ) Ion for ZrO_2 in F-T Reaction

CO hydrogenation was studied over zirconia catalysts. The catalysts, which were classed into three types of samples-the fresh, used and specially treated catalysts, were characterized by means of EPR spectroscopy. A strong signal at g⊥=1 .976 and g||=1.961, which was assigned to Zr3+ ion on the surface of ZrO2, was observed for the fresh catalysts. In contrast, unique strong and sharp signal at g=2.0024, which was assigned to dissociated H atom, also was observed for the used catalysts. Further verification of the assignments was carried out by EPR characterization of the specially treated catalysts. These results show that Zr3+ ion might involve in CO hydrogenation. Quantitative studies reveal that there is a close linear relation between Zr3+ ion and the selectivity to isobutene for the reaction over ZrO2. Finally, a possible mechanism of the catalytic reaction via a surface species Zr(Ⅲ)(CO)2 was proposed.