A SINGLE-CRYSTAL STUDY OF THE SILVER-CATALYZED SELECTIVE OXIDATION AND TOTAL OXIDATION OF ETHYLENE
A SINGLE-CRYSTAL STUDY OF THE SILVER-CATALYZED SELECTIVE OXIDATION AND TOTAL OXIDATION OF ETHYLENE
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DOI：
10.1016/0021-9517(85)90270-2
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发表时间：
1985-01-01
影响因子：
7.3
通讯作者：
LAMBERT, RM
中科院分区：
文献类型：
--
作者：
GRANT, RB;LAMBERT, RM
研究了在高达50Torr的压力下，在特征良好的Ag(111)单晶表面上的乙烯氧化。在没有促进剂和慢化剂的情况下，化学吸附的原子氧与吸附的乙烯反应生成环氧乙烷和(CO2+H2O)。化学吸附的氧气虽然存在，但似乎在这两个反应中都没有直接作用；亚表层氧的存在是选择性氧化所必需的，但不是完全氧化所必需的。间歇反应器研究部分和全部氧化的产率参数，这些参数与报道的传统负载型催化剂的值一致；选择性随着温度、压力和乙烯覆盖率的增加而降低。乙醛、醋酸和草酸被确定为二氧化碳形成过程中的反应中间体。C_2D_4氧化的结果证实了这些观察结果，观察到的动力学同位素效应表明，在乙烯和环氧乙烷的燃烧中，H-转移而不是C-C裂解是起决定作用的。探讨了可能的反应途径和反应机理。
Ethylene oxidation has been investigated on a well-characterised Ag(111) single crystal surface at pressures of up to 50 Torr. In the absence of promoters and moderators, chemisorbed atomic oxygen reacts withadsorbedethylene to yield both ethylene oxide and (CO2+ H2O). Chemisorbed dioxygen, though present, appears to play no direct role in either of these reactions; the presence of subsurface oxygen is necessary for selective oxidation but not for total oxidation. Batch reactor studies yield rate parameters for both partial and total oxidation which are consistent with the values reported for conventional supported catalysts; selectivity decreases with increasing temperature, pressure, and ethylene coverage. Acetaldehyde, acetic acid, and oxalic acid are identified as reaction intermediates in the pathway to CO2formation. Results for the oxidation of C2D4confirm these observations, and the observed kinetic isotope effect indicates that H-transfer rather than CC cleavage is rate-determining in the combustion of both ethylene and ethylene oxide. Possible reaction pathways and mechanisms are examined.