Vi. Bukhtiyarov et Vv. Kaichev, The combined application of XPS and TPD to study of oxygen adsorption on graphite-supported silver clusters, J MOL CAT A, 158(1), 2000, pp. 167-172
Oxygen adsorption on supported silver depending on the cluster sizes is stu
died by XPS and TPD using a model carbon-supported silver catalyst. It has
been shown that the electrophylic oxygen active in ethylene epoxidation is
produced on the small silver clusters (less than or equal to 100 Angstrom)
more effectively than on the bulk metal, most probably, due to formation of
subsurface oxygen. The desorption of the electrophylic oxygen at 450 K pro
ves the thermodynamic possibility of its participation into ethylene oxide
formation. Enlargement of the silver particles decreases the amount of subs
urface oxygen and results in the appearance of nucleophylic oxygen. These r
esults are used for discussion of the possible explanation of the size effe
ct in ethylene epoxidation over Ag/Al2O3 catalysts. (C) 2000 Elsevier Scien
ce B.V. All rights reserved.