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用XPS、ESR及高分辨固体NMR考察了在PdY沸石上乙烯双聚反应中活性中心钯离子的价态和位置。XPS的实验结果表明,双聚反应的活性价态为一价的Pd~+离子。同时,ESR的结果表明,用乙烯对样品进行预处理,在诱导期消失,双聚反应开始时,ESR谱上出现一新信号,它可能是乙烯与Pd~+配位形成的表面活性物种所引起的,它的生成导致诱导期的消失。NMR的结果证实了PdY沸石中阳离子在沸石笼之间的迁移现象,而XPS的实验结果又证实了钯离子在催化剂体相和表面间的迁移。提出了乙烯双聚反应中PdY催化剂的活化图式。
XPS, ESR and high resolution solid state NMR were used to investigate the valences and positions of Pd (superscript 2 +) in PdD zeolite. The experimental results of XPS show that the active valency of the dimerization reaction is a monovalent Pd ~ + ion. At the same time, the results of ESR showed that pretreatment of samples with ethylene disappeared during the induction period, and a new signal appeared on the ESR spectrum at the beginning of the dimerization reaction, which may be the surface active species formed by the coordination of ethylene and Pd ~ + Caused by its generation led to the disappearance of the induction period. The results of NMR confirmed the migration of cations in the PdY zeolite between the zeolite cages and the XPS experiments confirmed the migration of palladium ions between the bulk and the surface of the catalyst. Proposed ethylene polymerization of PdY catalyst activation diagram.