摘要
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 Pd^(2+)离子交换的 Y 型沸石,Lapidus 等借助于 XPS 实验证实了 Pd^0对乙烯双聚无活性,指出活性中心应为离子态的 Pd^+或 Pd^(2+)。虽然 Kevan
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 ethylene
dimerization,the appearance of a reactive induction period was not only due to
the 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-valent
ones.On disapperance of induction period and start of dimerization reactions,
two complex species,[=Ni(C_2H_4)_2]^+and[≡Ni(C_2H_4)_3]^+ were detected on the NiY
zeolite,which probably were active intermediates or their precursors of dimeriza-
tion.Accordingly,a mechanism for activation of NiX zeolite catalyst as well as a
reaction mechanism for ethylene dimerization under the reaction conditions
were proposed.
出处
《石油化工》
CAS
CSCD
北大核心
1990年第9期612-616,共5页
Petrochemical Technology
