摘要
电解银作为乙烯环氧化催化剂有较好的催化性能,微量助催化剂BaO能大大提高反应活性,但过多的Ba会抑制反应活性和选择性。XPS,ICP,AES结果表明:钡在表面富集,反应前钡以BaO和BaCO_3形式存在,反应时以BaCO_3存在于表面。催化稳定性实验表明BaO和BaCO_3的作用相同。用功函数测量研究了氧的吸附,结合活性数据阐明了钡添加剂的电子效应。
The activities for ethylene epoxidation of electrolytic silver and silver containing barium have been studied with a fixed bed reactor.Electrolytic silver as catalyst has good activity and selectivity for ethylene epoxidation to ethylene oxide.Barium compound as additive can improve the activity, but excessive barium decreases both the activity and selectivity.The X-ray photoelectron spectroscopy, Auger electron spectroscopy measurements show that barium is rich on surface and two kinds of barium compound (BaO, BaCO3) exist on unreacted catalyst, but BaO turns to BaCO3 completely after reaction.BaO and BaCO3 as additive have the same property in the system.Under UHV conditions, the adsorption of oxygen has been studied with work function change measurement.The results are explained by electron effect.
基金
国家自然科学基金
关键词
电解银
氧化钡
乙烯
环氧化
Electrolytic silver,barium oxide,ethylene,epoxidation
