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Why silver is the unique catalyst for ethylene epoxidation
- Ozbek, M.O., Onal, I., van Santen, R.A.
- Journal of catalysis 2011 v.284 no.2 pp. 230-235
- acetaldehyde, adsorption, catalysts, desorption, ethylene, ethylene oxide, isomerization, oxygen, silver
- The activities of Cu₂O(001), Ag₂O(001), and Au₂O(001) surfaces for direct ethylene epoxidation and alternative paths for EO isomerization are studied. Among these three oxide surfaces, only Ag₂O(001) surface enables direct path without a barrier. Au₂O cannot regenerate surface oxygen, and overall reaction on Cu₂O is endothermic. Furthermore, ring opening of ethylene oxide (EO) and subsequent acetaldehyde (AA) formation on Cu₂O is more favorable than EO desorption. Ethylene adsorption on an oxygen vacancy results in the oxametallacycle (OMC) formation, which causes AA formation and reduces EO selectivity. Cl adsorption removes these surface vacant sites and hence prevents the formation of the OMC intermediate.