【摘要】 <正> 一、前言对过渡金属交换的沸石催化剂上乙烯的双聚反应,众多的研究者均指出过渡金属离子直接参与催化活性中心的形成,但对于活性中心的价态却有许多不同的看法。对 Pd²⁺离子交换的 Y 型沸石,Lapidus 等借助于 XPS 实验证实了 Pd⁰对乙烯双聚无活性,指出活性中心应为离子态的 Pd⁺或 Pd²⁺。虽然 Kevan 等认为该更多还原

【Abstract】 Reaction active center valence and coordination state of ethylene dimeriza-tion over PdY and NiX zeolite catalysts were investigated with XPS and ESR. It was found that the active centers were uni-valent transition metal ions.Although uni-valent ions,Pd⁺ and Ni⁺ formed the active centers during ethylenedimerization,the appearance of a reactive induction period was not only due tothe coordination of uni-valent ions with ethylene to form active complex com-pounds,but rather also due to the reduction of bi-valent ions into uni-valentones.On disapperance of induction period and start of dimerization reactions,two complex species,[=Ni（C₂H₄）₂]⁺and[≡Ni（C₂H₄）₃]⁺ were detected on the NiYzeolite,which probably were active intermediates or their precursors of dimeriza-tion.Accordingly,a mechanism for activation of NiX zeolite catalyst as well as areaction mechanism for ethylene dimerization under the reaction conditionswere proposed.更多还原