摘要
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 Ag catalysts were prepared by different impregnation in order to discuss the effect of Cs different distributions. Relations between distribution of promoter Cs and catalytic properties are investigated by using XPS, XRD, pulse adsorption and microreador. The results show that Cs plays two types of promoting effects. Because of the d-d electronic interaction exists between Cs and Ag, it can efficiently adjust Ag valence states and control the ability of Ag output electron. So adsorbed β-O on the surface of Ag catalyst will possess appropriate negative charge, which can promote epoxidation to form EO. Meanwhile Cs can block acid center of the supporter to avoid isomerization of EO.
出处
《厦门大学学报（自然科学版）》
CAS
CSCD
北大核心
1992年第2期165-169,共5页
Journal of Xiamen University：Natural Science
关键词
铯
助催作用
银催化剂
Epoxidation of ethylene, Function of promoter Cs
