MECHANISM OF THE DECOMPOSITION OF PT-CO BIMETALLIC PARTICLES IN NAY ZEOLITES

The decomposition mechanism of bimetallic particles encapsulated in th e Pt-Co/NaY zeolite system is discussed. The large decrease in hydroge n uptake observed in TPR measurements taken before and after mild oxid ation is interpreted in the light of the decomposition of bimetallic p articles. During mild oxidation, Co2+ ions are first enriched on the s urface of the bimetallic particles, then they become detached and migr ate to the hexagonal or sodalite cages leaving Pt2+-covered Pt-0 kerne ls in the supercage. No agglomeration or migration of these kernels to the external surface was observed.