Effect of particle size upon catalytic and electronic properties of supported Ag catalysts: combined catalytic, 109Ag NMR and quantum chemistry studies

Abstract

The rate of ethylene epoxidation over Ag Al 2O 3 supported catalysts demonstrates the drastic increase at a mean size of Ag particles about 400–500 Å. The integral intensity of the 109Ag NMR line from Ag metal particles of the same catalysts increases in the same range of particle sizes. This is due to the large line broadening of the signal from the Ag particles of which the sizes are less than 400–500 Å. The self-consistent calculations of the electronic structure of semi-infinite Ag(111) crystal show the large deviation of the local density of electronic states and 109Ag NMR Knight shifts for the first surface layers of Ag compared with Ag bulk.