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 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 284 Issue: 2
  • Publication Date: 2011
  • Doi Number: 10.1016/j.jcat.2011.08.004
  • Journal Name: JOURNAL OF CATALYSIS
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • 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)
  • Middle East Technical University Affiliated: Yes

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.