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用XPS、XRD、脉冲吸附和微反动力学评价等方法,研究铯的不同含量和分布对催化剂性能的影响。结果表明Cs在银催化剂表面含量和分布状态的不同,可能具有不同的助催作用本质,由于Cs与Ag间存在着d-d电子相互作用,能有效地调节Ag的价态和电子输出能力,有利于选择氧化生成环氧乙烷(EO),同时Cs能中和载体表面使EO异构化的酸中心,因此设法让催化剂表面存在适量的Cs并使Cs-Ag间有适当的距离是制备高选择性乙烯环氧化银催化剂的关键。
The effects of different contents and distribution of cesium on the catalyst performance were studied by XPS, XRD, pulse adsorption and micro-inverse kinetic evaluation. The results show that the content and distribution of Cs on the silver catalyst surface may have different nature of promoters. Due to the existence of dd electron interaction between Cs and Ag, Cs can effectively regulate the valence state and electronic output capacity of Ag, which is in favor of Selective oxidation to ethylene oxide (EO) while Cs neutralizes the isomerised acid sites on the support surface and therefore attempts to provide a suitable amount of Cs on the surface of the catalyst and a suitable distance between Cs-Ag Sex ethylene silver oxide catalyst key.