Why silver is the unique catalyst for ethylene epoxidation


Ozbek M. O. , ÖNAL I. , van Santen R. A.

JOURNAL OF CATALYSIS, vol.284, no.2, pp.230-235, 2011 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 284 Issue: 2
  • Publication Date: 2011
  • Doi Number: 10.1016/j.jcat.2011.08.004
  • Title of Journal : JOURNAL OF CATALYSIS
  • Page Numbers: pp.230-235
  • Keywords: DFT, Cu(2)O, Ag(2)O, Au(2)O, Ethylene, Ethylene oxide, Oxide surface, DENSITY-FUNCTIONAL THEORY, HETEROGENEOUS EPOXIDATION, SUBSURFACE OXYGEN, SUPPORTED SILVER, ETHENE EPOXIDATION, OXIDATION, SURFACE, OXIDE, SELECTIVITY, AG(111)

Abstract

The activities of Cu(2)O(001), Ag(2)O(001), and Au(2)O(001) surfaces for direct ethylene epoxidation and alternative paths for EO isomerization are studied. Among these three oxide surfaces, only Ag(2)O(001) surface enables direct path without a barrier. Au(2)O cannot regenerate surface oxygen, and overall reaction on Cu(2)O is endothermic. Furthermore, ring opening of ethylene oxide (EO) and subsequent acetaldehyde (AA) formation on Cu(2)O 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. (C) 2011 Elsevier Inc. All rights reserved.