In SituControlled Promotion of Catalyst Surfaces via NEMCA: The Effect of Na on the Ag-Catalyzed Ethylene Epoxidation in the Presence of Chlorine Moderators
In SituControlled Promotion of Catalyst Surfaces via NEMCA: The Effect of Na on the Ag-Catalyzed Ethylene Epoxidation in the Presence of Chlorine Moderators
复制标题
通过 NEMCA 对催化剂表面进行原位控制促进：氯缓和剂存在下 Na 对银催化乙烯环氧化反应的影响
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
C. Vayenas
中科院分区：
文献类型：
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作者：
Ch. Karavasilis;S. Bebelis;C. Vayenas
研究了在Na+导体β " -Al2O3上沉积的Ag薄膜，在温度240 ~ 280℃、总压500 kPa、氯代烃缓和剂存在的条件下，乙烯环氧化过程中，非法拉第电化学修饰对催化活性的影响。β”- al2o3载体允许控制和可逆的恒电位引入不同水平的钠在Ag催化剂表面。结果表明，0.03的钠含量可提高环氧化反应的速率，而不显著影响完全氧化的速率。钠对乙烯环氧化反应的促进指数高达40。当θNa = 0.03，二氯乙烷浓度为1 ppm时，对环氧乙烷的选择性最高（88%）。本文在综述前人对乙烯环氧化反应的原位促进研究的基础上，结合目前乙烯环氧化反应机理的主流观点，讨论了钠和氯的促进和协同作用。
The effect of non-Faradaic electrochemical modification of catalytic activity, orin situcontrolled promotion, was investigated during ethylene epoxidation on Ag films deposited on β′′-Al2O3, a Na+conductor, at temperatures 240 to 280°C and 500 kPa total pressure in the presence of chlorinated hydrocarbon moderators. The β′′-Al2O3support permits controlled and reversible potentiostatic introduction of various levels of sodium on the Ag catalyst surface. It was found that sodium coverages up to 0.03 enhance the rate of epoxidation without affecting significantly the rate of complete oxidation. The promotion index of sodium for ethylene epoxidation is up to 40. Maximum selectivity to ethylene oxide (88%) is obtained for θNa = 0.03 and 1 ppm dichloroethane. The promoting and synergistic action of sodium and chlorine is discussed on the basis of previousin situcontrolled promotion studies and the prevailing ideas about the mechanism of ethylene epoxidation.