PREPARATION AND CHARACTERIZATION OF DISPERSED RUTHENIUM METAL SUPPORTED ON EX-BOEHMITE GAMMA-ALUMINA

Ru-3(CO)(12) supported on hydroxylated gamma-Al2O3 by an impregnation procedure was found to decompose into several subcarbonylic species; m ainly Ru2+(CO)(2), Ru-0(CO)(2) and Ru-3(n+) (CO)(6), as revealed by FT IR spectroscopy. Ru2+ (CO)(2) is a mononuclear species, Ru-0(CO)(2) co ntains Ru-Ru bonds and Ru-3(n+) (CO)(6) probably retains the triangula r Ru-3 skeleton. Thermal decomposition at 773 K in a dynamic vacuum ca uses decarbonylation of the supported species and formation of small m etal aggregates. Part of the metal is oxidized and the rest remains as zerovalent without the need for reduction treatments. The particle si ze distribution of the metal aggregates shows a maximum at 3.5 nm, as determined by transmission electron microscopy. (C) 1998 Elsevier Scie nce Limited. All rights reserved.