EFFECT OF PARTICLE-SIZE UPON CATALYTIC AND ELECTRONIC-PROPERTIES OF SUPPORTED AG CATALYSTS - COMBINED CATALYTIC, AG-109 NMR AND QUANTUM-CHEMISTRY STUDIES

The rate of ethylene epoxidation over Ag/Al2O3 supported catalysts dem onstrates the drastic increase at a mean size of Ag particles about 40 0-500 Angstrom. The integral intensity of the Ag-109 NMR line from Ag metal particles of the same catalysts increases in the same range of p article 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 Angstro m. The self-consistent calculations of the electronic structure of sem i-infinite Ag(lll) crystal show the large deviation of the local densi ty of electronic states and Ag-109 MMR Knight shifts for the first sur face layers of Ag compared with Ag bulk.